Term
|
Definition
| text items on the map that are dynamically placed and whose text values are derived from one or more feature attributes. |
|
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Term
|
Definition
| references to data sources such as point, line and polygon shapefiles; geodatabase feature classes, raster images; and so forth, representing spatial features that can be displayed on a map. |
|
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Term
| What are absolute paths and how do they work? |
|
Definition
| saved as "C:\Gistutorial/Tutorial1.mxd" these maps gather data and layers from other locations using the full driver name so that all people wanting to use an absolute path map must do so on the same computer or have the data on their computer in the exact same folder structure. Not good for a computer lab classroom environment. |
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Term
| What are relative paths and how do they work? |
|
Definition
| Saved as "\Gistutorial/Tutorial1.mxd" relative paths in a map specific the location of the layers relative to the current location on disk of the map document (the .mxd file). The do not contain drivers names, like C or D, they enable the map and it's associated data to point to the same directory structure regardless of the driver the map resides on. If a project is moved to a new driver ArcMap will still be able to find the maps and their data by traversing relative paths. Also for easy sharing and copying. |
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Term
| What file is a map document saved as? |
|
Definition
|
|
Term
| What is a choropleth map? |
|
Definition
| A map in which polygon areas are colored or shaded to represent attribute values. |
|
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Term
| What are group layers and why use them? |
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Definition
| Group layers behave similarly to regular layers but they contain within them multiple layers allowing for better organization of the layers in your map. |
|
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Term
| How do you save a layer file? |
|
Definition
| using the .lyr extension under a right click "save as layer" file option. |
|
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Term
| what's the difference between minimum and maximum range? |
|
Definition
| minimum scale makes it so the layer is only displayed when zoomed in this close or closer, zooming out farther than the minimum scale will hide the later. Max scale is the opposite this makes it so the layer is not displayed when zoomed in beyond the maximum scale setting, zooming out will return the layer to view. |
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Term
|
Definition
| Also known as point maps, these maps show the exact locations of data or evens using individual point markers for each record . They are the symbology symbols as opposed to graduated color symbology. |
|
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Term
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Definition
| a collection of maps and database tables stored in a relational database management system. These are different than file-based systems such as shapefiles. |
|
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Term
| Why do we use ArcCatalog? |
|
Definition
| Many of the file maintenance tasks for which you would normally use My computer or Windows Explorer must be done using ArcCatalog. This is because a change in a single layer often affects several tables in the geodatabase, and Arc Catalog will maintain these relationships. |
|
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Term
| What are some major file formates used to create GIS basemaps? |
|
Definition
| Shapefiles, ArcInfo coverages, CAD files and Raster Images. |
|
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Term
| What is ESRI and why do we bother with them? |
|
Definition
| ESRI sit he world leader in GIS and mapping software. It maintains a website that is a useful resource for obtaining information and data used to create GIS maps. It maintains the geography network which provides valuable free and inexpensive GIS data. |
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Term
|
Definition
Topologically Integrated Geographic Encoding and Referencing, or TIGER, is a format used by the United States Census Bureau to describe land attributes such as roads, buildings, rivers, and lakes, as well as areas such as census tracts. TIGER was developed to support and improve the Bureau's process of taking the Decennial Census.
The TIGER files do not contain the census demographic data, but merely the map data. GIS can be used to merge census demographics or other data sources with the TIGER files to create maps and conduct analysis. |
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Term
|
Definition
| A type of GIS vector data format used to store geographic features. Typically it is used to store one or more feature classes that are topographically or thematically related. You can add coverage data to ArcMap and use it for analysis and presentation but coverage data cannot be edited with ArcMap. Can be exported as shapefiles or geodatabase feature classes to edit their attribute tables or geometry. |
|
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Term
|
Definition
another type of GIS vector data format used to store geographic features. Unlike coverage, which are made up of a collection of feature classes, a shapefile can represent only one feature class. Shapefiles can be created, edited and analyzed using ArcView.
Shape files consist of at least three files. a .dbf file, a .shx file and a .shp file. .dbf stores the attributes, .shp stores the geometry of the features and .shx sotres an index of spatial geometry. |
|
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Term
|
Definition
another type of GIS vector data format used to store geographic features. Unlike coverage, which are made up of a collection of feature classes, a shapefile can represent only one feature class. Shapefiles can be created, edited and analyzed using ArcView.
Shape files consist of at least three files. a .dbf file, a .shx file and a .shp file. .dbf stores the attributes, .shp stores the geometry of the features and .shx sotres an index of spatial geometry. |
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Term
| What are interchange (.e00) files? |
|
Definition
| Many local planning agencies and GIS consultants provide their coverage data as interchange (.e00) files. Interchangeable files are the preferred method for sharing coverage data because all of the folders and files associated with a coverage are placed into one .e00. ArcView can convert the file back into coverage. |
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Term
| What is annotation and how does it differ from Labels? |
|
Definition
| This allows for full control over where labels are placed in ArcGIS map and makes them independent from the layer they are labeling. |
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Term
|
Definition
| Computer-aided design files. ArcMap can view but not edit CAD files. They can be added in one of two formats: as native AutoCAD (.dwg) or as Drawing Exchange Files (.dxf). You can export shapefiles to a .dxf format which can allow people working with CAD software to use your data. |
|
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Term
|
Definition
| Tabular point data that contains x,y coordinates. Can be added to a map and can be collected using a Global positioning Device or GPS. |
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Term
| What are the two types of coordinate systems? |
|
Definition
| Geographic and projected. |
|
|
Term
| Geographic vs Projected Coordinate Systems? |
|
Definition
| Geographic Coordinate Systems use latitude and longitude coordinates on the surface of a sphere while projected coordinate systems use a mathematical conversion to transform latitude and longitude coordinates to a flat surface. Maps obtained from the U.S. Census are typically in geographic coordinates while local maps are typically based on projected coordinate systems. |
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Term
| Primary purpose for Mercator Projection? |
|
Definition
| Navigation because straight lines on the projection are accurate compass bearings. greatly distorts the polar regions and distances. Is conformal. |
|
|
Term
| Primary purpose for Mercator Projection? |
|
Definition
| Navigation because straight lines on the projection are accurate compass bearings. greatly distorts the polar regions and distances. Is conformal. |
|
|
Term
| Hammer-Aitoff Projection? |
|
Definition
| Is good for use on a world map being an equal area projection and preserving area but it greatly distorts direction and distance. |
|
|
Term
| Importance of defining projections? |
|
Definition
| All GIS layers should have a projection defined, but sometimes you will receive a shape file or other GIS layer that does not have a projection (.prj) file and you need to assign this yourself. |
|
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Term
| State Plan Coordinate system? |
|
Definition
| A series of projections, it dives the 50 US states, Puerto Rico and the Virgin Islands into more than 120 numbered sections, refereed to as zones, each with its own finely tuned projection. Used by most local government agencies. |
|
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Term
|
Definition
| The Universal Transverse Mercator was developed by the US military late in the 1940s. It includes 60 longitudinal zones defined by meridians that are 6* Wide. Quite good for areas about the size of a state or smaller. |
|
|
Term
|
Definition
| The Universal Transverse Mercator was developed by the US military late in the 1940s. It includes 60 longitudinal zones defined by meridians that are 6* Wide. Quite good for areas about the size of a state or smaller. |
|
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Term
|
Definition
| Metadata is often described as data about the data. Arc Catalog is used to create and view Metadata. Though some information such as spatial extent can be automatically created by Arc most Meta Data muse be entered manually. |
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Term
| Where can I get attribute data from? |
|
Definition
| Arc GIS allows direct use of data in a variety of formats and the program works with them as tables including form text (.txt, .asc, .csv, and .tab), dBASE (.dbf), Excel (.xls) and Access (.mdb) |
|
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Term
| Digitizing is useful for what? |
|
Definition
| For creating and editing spatial/vector features such as points, lines and polygons. |
|
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Term
|
Definition
| information that is collected "on location." In remote sensing, this is especially important in order to relate image data to real features and materials on the ground. The collection of ground-truth data enables calibration of remote-sensing data, and aids in the interpretation and analysis of what is being sensed. |
|
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Term
|
Definition
Geographic – the real world or spatial realities
Information – data and information and their meaning and use
Systems – computer technology and its supporting infrastructure |
|
|
Term
| What is a brief history of when GIS started and how it has developed? |
|
Definition
1960’s – 1975: pioneering stage
1973 – early 1980’s: experiment and practice
1982 – late 1980s: commercial dominance
1990s to 2000: user dominance and vendor competition |
|
|
Term
| What is Geographical Information Systems or GIS? |
|
Definition
| a computer based technology and methodology for collecting, managing, analyzing, modeling and presenting geographic data for a wide range of applications |
|
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Term
|
Definition
| anything that can be located on earth (or elsewhere) and any description or accompanying information |
|
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Term
|
Definition
| a collection of facts in a database, the raw and unprocessed observations from a survey. |
|
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Term
|
Definition
| a collection of related data, usually associated with a specific topic |
|
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Term
|
Definition
| the meaning or interpretation of data; the knowledge obtained from data after it has undergone some processing called either analysis or synthesis |
|
|
Term
| List some basic GIS operations (7): |
|
Definition
1. Data Collection
2. Storage and management
3. Retrieval
4. Conversion
5. Analysis
6. Modeling
7. Display |
|
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Term
|
Definition
| gathering data from many sources such as remote sensing from satellites, field work, the internet, published journals, expert opinion. |
|
|
Term
| Describe Data Storage and management: |
|
Definition
| administering and keeping track of data including the integration of many different types of data into a common database. |
|
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Term
|
Definition
| changing data from one form to another e.g. converting one geographic projection to another, rescaling, reclassifying |
|
|
Term
| What is Data Retrieval and Analysis? |
|
Definition
| Data Retrieval – easy and efficient selection and viewing of data in a variety of ways such as using the computer monitor display, printed maps and the internet. VS Data Analysis- analyzing data to produce insight and new information using various techniques. ((Both can be used when collecting new data for a new purpose)) |
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Term
| What is Data Modelling and Display? |
|
Definition
| Modeling – simplifying data to understand how things work or explain what data means – e.g. contour map from elevation data is a model of an area based on a few points of data vs Display- presenting data in various ways for ease of understanding – e.g. maps, graphs and reports |
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Term
| List some Geographic Information Technologies: |
|
Definition
| GPS, remote sensing and GIS |
|
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Term
| What systems are a part of Geographic information systems? |
|
Definition
| computer systems, software, spatial data, data management and analysis procedures, and the organization and people to operate the GIS. No GIS exists in isolation, there must be people to plan, implement and operate the system. |
|
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Term
| classified the three types of GIS analysis procedures: |
|
Definition
(1)Those used for storage and retrieval
(2)Constrained queries that allow user to look at patterns in data
(3) Modeling procedures for the prediction of what data might be at a different time or place. |
|
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Term
| What is Data input vs output? |
|
Definition
| copying maps using a digitizer, text and manual data entry using a key board, scanners, GPS, internet, CD’s and so on. VS. Output: ranges from data plotter, storage, internet and virtual reality |
|
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Term
|
Definition
Spatial data have a specific location according to some world geographic reference system or address system. (Davis 2001)
p.s. Maps are a traditional method for storing, analyzing and presenting spatial data. |
|
|
Term
| List the 8 steps to follow when producing a Map: |
|
Definition
1.Establish the purpose of the map
2.Define the scale at which map is to be displayed
3.Select features to display on the map
4.Choose a method to represent these features
5.Generalize the features in 2D
6.Adopt a projection and datum
7.Apply a spatial referencing system
8.Annotate the map with keys, legends and text
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|
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Term
| What is the Purpose of Maps? |
|
Definition
| In most cases the purpose of a map is to turn data into information which can be communicated to a third person. |
|
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Term
|
Definition
| Scale is the ratio of a distance on the map to the corresponding distance on the ground. Scale gives an indication of how much smaller than reality a map is. (All maps are smaller than the reality that they represent) |
|
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Term
|
Definition
| shows a large area on the earth’s surface (e.g. 1:250,000 or 1:1,000,000 or a world map) |
|
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Term
|
Definition
| shows a small area on the earths surface (e.g. 1:10,000 or 1:5000 or a city map such as Auckland) |
|
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Term
|
Definition
| It is closely tied to the precision and accuracy of your project where Precision is defined by the original scale data was collected and cannot be improved by ‘zooming in’. Additionally if you use several data sets, the smallest scale determines the accuracy of the project. The Purpose of your project determines what scale to use and the original scale needs to be documented in the metadata. |
|
|
Term
| What are the 3 basic symbols maps use to represent real world features? |
|
Definition
| Points, Lines and Areas (polygons) |
|
|
Term
|
Definition
| 0 dimensional. Are used to represent features that are too small to be represented as areas at the given scale of the map. |
|
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Term
|
Definition
| one dimensional having length. They represent features that are linear in nature. A line is an ordered set of points – or a string of x,y coordinates that are joined together in order and usually connected with straight lines. |
|
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Term
|
Definition
| 2 dimensional with length and width. They are represented by a closed set of lines. Can be referred to as polygons. They are a 2D feature with at least 3 sides, have area and perimeter. They can be adjacent (share a common boundary) or island polygons. |
|
|
Term
| Generalization and Spatial Data: |
|
Definition
All spatial data are a generalisation or simplification of real world features.
All data sources used in GIS contain inherent generalizations.
Generalizations are needed to maintain clarity in maps. |
|
|
Term
| The ___ the scale the nearer the objects are to their actual size? |
|
Definition
| Larger aka a 1:50m map (large scale) is closer to actual size than a 1:50000m map (small scale). |
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Term
| Why do some maps use Lats/Longs(degrees) while others us Easting and Northings(meters)? |
|
Definition
| The 1st type use geographic coordinate systems (3D) while the latter use projected coordinate systems (2D). |
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Term
| What do you need to know to use a Geographic Coordinate System? |
|
Definition
| need to have a datum to create an ellipsoid. You need a prime meridian. And in the end you get location in angular units. |
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Term
| What do you need to know to use a projected coordinate system? |
|
Definition
| You need projection parameters(origin, east& northing, projection type, ect) and you get locations in linear units. |
|
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Term
| Describe Geo Coordinate Systems. |
|
Definition
Defines locations using a 3-D spherical surface. Where a feature is referenced by its longitude and latitude values.
Longitude and latitude are angles measured from the Earth’s center to a point on the Earth’s surface.
Measured in decimal degrees or in deg, min, and seconds. Latitudes measured relative to the Equator &Longitudes relative to the Prime Meridian. |
|
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Term
| What are the two main Problems with Geographic Coordinate Systems? |
|
Definition
(1) Lat & Long OK for locating positions on Earth, BUT They are Not uniform units of measure. They vary by location.
Therefore, you can’t measure distances, areas, or direction between two points. (2) Earth is not evenly round, it's actually a lumpy spheroid!
South Pole closer to Equator than North Pole. |
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Term
| What are the four concepts of the earth? |
|
Definition
| Terrestrial surface >> Geoid >> Datum >> Ellipsoid |
|
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Term
|
Definition
| composition of the Earth is not uniform, it varies from place to place - mountain ranges, ocean trenches THEREFORE gravity field not uniform |
|
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Term
|
Definition
| the surface that has a constant value of gravity, you can’t see it but it’s there |
|
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Term
|
Definition
| a mathematical model (formula) that describes the size and shape of the Earth. very complex, their are multiple models fitted to different parts of the earth! Creates multiple geographic coordinate systems. |
|
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Term
|
Definition
| a reference surface on which to base mapping and GIS. >> created from the datum model. |
|
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Term
| Local Geodetic datum vs Geocentric datum |
|
Definition
| aligns the spheroid to fit to a particular area ex NAD27 the best fit for North America vs uses the Earth’s center of mass as the origin ex NZGD 2000. |
|
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Term
| Explain Projected Coordinate systems: |
|
Definition
| A map projection is used to portray all or part of the spherical Earth on a flat surface. Cannot be done without some distortion.Every projection has its own set of advantages and disadvantages and we must selected the one that best suits are needs (i.e. reducing distortions for the most important features). |
|
|
Term
|
Definition
| Projected coordinate systems seek to locate data from a spherical earth onto a flat surface, where units of data are similar throughout the dataset (unlike geographic coordinate systems). |
|
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Term
| Name some Projection parameters: |
|
Definition
(1) Origin - center from which measurements can originate
(2) Easting and Northing – linear distance east and north of origin
(3) False Easting and False Northing – used to avoid negative coordinates |
|
|
Term
| What are the types of projection surfaces? |
|
Definition
Cone, Cylinder or Parameter. A point or line of contact (i.e. tangent) is created when surface is combined with sphere. There is no distortion at contact points but distortion increases
away from contact points. |
|
|
Term
| What do projections distort? |
|
Definition
| Shape, Area, Distance and Direction. |
|
|
Term
| List the 4 main types of projection properties: |
|
Definition
| Conformal, Equal Area, Equidistant and Direction. |
|
|
Term
| Conformal vs Direction projections |
|
Definition
Conformal maintains shape of small areas by preserving angles locally
Examples (conformal maps preserve local shape) vs direction maintains certain true direction. |
|
|
Term
| Equidistant vs Equal Area Projections |
|
Definition
| Equidistant maintains certain distances vs equal-area maps maintain area. (equal-area or equivalent maps retain all areas at the same scale) |
|
|
Term
| Normal Mercator Projection |
|
Definition
Cylindrical & projected on a cylinder tangent to the Equator. This projection is conformal. Was used for navigation or maps of equatorial regions. Because any straight line on the map is a rhumb line (line of constant direction) and directions along a rhumb line are true between any two points on the map. Distances are true only along the Equator, but are reasonably correct within 15° of Equator. Large areas are distorted. Distortion increases away from Equator and is extreme in polar regions. Note the map is not perspective, equal area, or equidistant.
Equator and other parallels are straight lines and meet meridians at right angles. |
|
|
Term
| Uses of the different Mercator Projections |
|
Definition
Normal – good for equatorial / East-West regions while
Transverse – good for North-South regions while
Oblique – good for landmasses with other angles |
|
|
Term
| What is the chosen tangent of a Traverse Mercator? |
|
Definition
| Projected on cylinder tangent to a chosen meridian. Is conformal. |
|
|
Term
| Highlights of the Transverse Mercator |
|
Definition
| Since the central meridian of the Transverse Mercator can be chosen arbitrarily it may be used to construct highly accurate maps (of narrow width) anywhere on the globe.Distances are true only along the central meridian selected by the mapmaker or else along two lines parallel to it. All distances, directions, shapes, and areas are reasonably accurate within 15° of the central meridian. Distortion of distances, directions, and size of areas increases rapidly outside the 15° band. |
|
|
Term
| UTM (Universal Transverse Mercator) Projection |
|
Definition
The system divides the Earth into 60 zones (6° wide), then a rectangular grid within each zone. Each zone is based on a specifically defined transverse Mercator projection.
Distance, shape, area all have <0.04% distortion.
Good for area with greater north-south extent. |
|
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Term
|
Definition
Conic. Projected on a cone tangent at two standard parallels. Is also conformal. Often used to show a country or region that is mainly east-west in extent.Distances true only along standard parallels; reasonably accurate elsewhere in limited regions.
Directions reasonably accurate.
Distortion of shapes and areas minimal but increases away from standard parallels. |
|
|
Term
|
Definition
conic & Projected on a cone tangent at one parallel. Projection property is equidistant.
Used in atlases to show areas in the middle latitudes. Good for showing regions within a few degrees of latitude and lying on one side of the Equator.
Distances are true only along all meridians and along one or two standard parallels.
Directions, shapes and areas are reasonably accurate, but distortion increases away from standard parallels. |
|
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Term
|
Definition
Azimuthal- Geometrically projected onto a plane. Point of projection is at infinity. Used for perspective views of the Earth, Moon etc.
Directions are true only from center point of projection. Scale decreases along all lines radiating from center point of projection.
Areas and shapes are distorted by perspective; distortion increases away from center point.
Map is perspective but not conformal or equal area.
The Orthographic projection was known to Egyptians and Greeks 2,000 years ago. |
|
|
Term
|
Definition
States are broken into regions and different projection used for each region:
tall, narrow regions = Transverse Mercator vs
wide, short regions = Lambert conformal conic vs
Alaska panhandle = oblique Mercator |
|
|
Term
| How do you find out what coordinates system is your data? |
|
Definition
| MetaData! Should contain info on the datum and projection of a dataset. |
|
|
Term
| Converting from one coordinate system to another: |
|
Definition
| Coordinate system can be defined in ArcToolbox. Data can be projected (converted) in ArcToolbox as well. |
|
|
Term
| What are the two basic methods of storing real world data? |
|
Definition
|
|
Term
|
Definition
| in the RASTER model, you create a grid of equally sized squares or CELLS whose values correspond to the locations of real world features vs in the VECTOR model, you record the x,y coordinates of points, lines and polygons and store information about how they are connected. |
|
|
Term
|
Definition
Stores features as VALUES
within an equally spaced GRID. The position of each CELL within the grid stores its relative location and each cell must have a value assigned to it. X,Y coordinates are only needed to link the position of the grid boundary to real world >> all features are stored relatively. ). A value is stored in each cell indicating whether a feature is located there or not, and/or what that feature is. |
|
|
Term
|
Definition
| dividing the area of interest into equally-sized cells each having the same shape & area. Note, though, that each cell must have the same shape, and the same-sized cell! Squares are the shape most commonly used to tessellate the plane in raster GIS, and a square grid is called a raster grid. Thus, this is called the raster format. |
|
|
Term
|
Definition
| In the vector model, the locations of features are stored with x,y coordinates of points, which are connected to form lines, which are combined to form polygons. Each point is defined by an x, y coordinate (or a latitude, longitude or whatever coordinate system you’re using). Each feature (whether is is a point, line or polygon) is assigned an unique identification number. This is used by the GIS to tell each feature apart. These ID numbers are typically assigned in order of the position of each feature - number 1 usually is assigned to the feature that is located closest to the top, left section of the map extent. only locations where a feature exists are recorded (unlike in raster). |
|
|
Term
| Comparing features in different layers with raster vs vector |
|
Definition
| Raster: You need a specific layer for each attribute of interest and must have the same sized cells to compare features between grids! vs Vector each feature has a range of values or attributes associated to it. Vector features can be compared even if they are different sizes as long as the coordinate systems are the same. |
|
|
Term
| What are the major 4 differences between the two formats(Raster vs Vector)? |
|
Definition
1) How precisely you can store the locations of features in the GIS.
2) How much space your database will take up in the computer.
3) How long it will usually take to perform spatial analysis tasks.
4) How well you can represent the type of features that you want to show. |
|
|
Term
| Precision in data formats |
|
Definition
| If you know its position precisely, next time you go to that place you will end up nearly exactly back in the same spot. If you don’t you might end up near the same spot but not exactly on it. Vector can be a lot more precise than Raster(has to be 2 dimensional cells, bad for lines and exact distances). |
|
|
Term
| Resolution of Vector vs Raster |
|
Definition
Resolution is similar to MAP SCALE in that it refers to the level of detail of the information in your GIS database For Vector: resolution is just the shortest line that you can draw between any two points. RASTER =
size of each cell in the grid. Vector has no limit to how much resolution you can store |
|
|
Term
| Space for different formats |
|
Definition
| Vectors can take up less space for a higher resolution pictures than raster because vectors only need to store data where something exists. |
|
|
Term
|
Definition
| Maybe be less precise and take up more space however one major benefit of raster is that most spatial analysis tasks are completed much FASTER in RASTER! (( However ), if you need to do large spatial queries that involve lots of themes that all relate to the same spatial features, it may actually be faster in vector (because the computer could find all the information for the query in a single linked table, rather than a stack of different data layers).)) |
|
|
Term
| Boundaries and data formats |
|
Definition
| Most features with abrupt boundaries are best represented in GIS as VECTOR OBJECTS. While features with gradual boundaries are best represented as Raster fields. |
|
|
Term
| Job uses of Vector GIS vs Raster GIS |
|
Definition
| Vector GIS tends to form the basis of management information systems: its stores facts. Works with established facts or knowledge. Often used in resource management and LIS. (ArcInfo) While Raster GIS is the area of scientific work in GIS – advanced spatial analysis, predictive modelling, graphical simulation, visualisation, image analysis, and terrain analysis. Algorithmic and image-based approaches to data analysis are used with raster. (ArcGRID) |
|
|
Term
|
Definition
Use vector if the features you want to represent in GIS have abrupt boundaries because it can record those boundaries with greater precision.
Vector is also best if you need to examine spatial relationships between features along a network (a network is just a series of connected objects - like a system of roads or streams, or even fault lines).
if you need to maintain a large spatial database, with lots of attributes (themes) linked to a single set of features, vector is better because it allows you to locate each feature precisely and link as many attributes as you need.
And vector is more efficient to use if you need to create high quality, detailed maps, say where you need to show lots of detailed lines. |
|
|
Term
| When to use Raster Format? |
|
Definition
| You would use raster if the features you need to represent in your GIS have gradual boundaries, and they vary along a continuous surface. perhaps you want to map how depth varies across the Great Barrier Reef. This would be much more effectively done using raster format.Also, since most spatial analysis tasks are FASTER in RASTER, you would use raster if you need to combine lots of data layers quickly and cheaply. Satellite images in your GIS requires processing them in raster (at least to start). This is the case because satellites record information about the earth’s surface and send it back to computers on the ground in raster format. |
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Term
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Definition
| To compare layers they must have the same format. However you can display both types together in a map. If you want you can also store in one form (vector) and process in another (raster). |
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Term
| Name some spatial relationships: |
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Definition
| Distance,Distribution (dispersal or range of features), Density (number of items per unit area), and Pattern (consistent arrangement of features) |
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Term
| What are Proximity relationships? |
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Definition
Proximity refers to features that may have an association because they are spatially close to each other. Also referred to as “neighborhood”. The closer features are to one another the more likely they have a relationship, the further apart the less likelihood of relationship. Three common proximity relationships are: Connectivity, Contiguity, and Adjacency.
C |
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Term
| Describe the three common proximity relationships? |
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Definition
| (1)Connectivity – features that touch or connect, (2) Contiguity – degree of connection and (3) Adjacency – nearness of features that are close together |
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Term
| What does a feature know when it has Topology? |
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Definition
1. Knows where it is - a features position is part of the data 2. Knows what is around it - the connected and surrounding features are recognised
3. Has recognized spatial relationships
4. Has length, distance, perimeter and area information
5. Knows how to get around - gets from one location to another using connections and paths
6. Understands its environment. Understands its environment by virtue of the connections and spatial relationships (its surroundings), topology identifies features and uses their attributes to accomplish various spatial analysis tasks. |
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Term
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Definition
| In 1736 it was developed by mathematician Leonhard Euler. In 1970 the US Census Bureau pioneered the application of mathematical topology to maps to reduce the errors in tabulating massive amounts of census data. |
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Term
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Definition
| topology in GIS is generally defined as the spatial relationships between adjacent or neighboring features. In GIS, topology is the special data structure that establishes connections and links for the nodes and chains in order to recognize spatial relationships among geographic features. |
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Term
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Definition
| It is easy for humans to follow lines and identify features along the way – a computer is not as inherently intelligent and needs special programming aka TOPOLOGY! |
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Term
| How do you apply Topology? |
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Definition
| Topology is applied or “built” usually after digitizing. At first they are lines without connections aka the Spaghetti Model. Because features can exist only on a 2D plane, lines that cross are broken into separate lines that terminate at nodes representing intersections rather than simple vertices. |
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Term
|
Definition
1) they provide an automated way to handle digitizing and editing errors and artifacts. 2) they reduce data storage for polygons because boundaries between adjacent polygons are stored only once. 3)they enable advanced spatial analyses such as adjacency, connectivity, and containment.
4) they contain space-filling, non-overlapping polygons. |
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Term
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Definition
| Digitizing is the digital tracing of maps and is usually the primary means of entering map data. |
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Term
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Definition
| Topology can work on an integrated set of line features, called a network. Topology provides the connections and routing analysis. Network topology combined with GPS is used in new car direction systems, enhanced emergency response, transportation planning… |
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Term
| Sources of GIS Data include: |
|
Definition
Maps
Field data
Digital products
Tabular data
Reports
Human input
Remote sensing |
|
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Term
| What is one of the major sources of GIS data and what are its advantages? |
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Definition
| Remote Sensing. Advantageous because Images cover large areas (satellite images),have consistent data quality and conditions of collection, are delivered to end users very quickly and are permanent record that can be checked and used for a long time. Additionally they are good for Gather data from difficult or inaccessible areas. Moreover Remote sensing equipment can obtain information from a much great portion of the spectrum than the human eye can see. |
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Term
| What parts of the EM spectrum can remote sensing detect? |
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Definition
Visible range from blue to red:
Great for location photos. Near infrared:
Plant stress and health is apparent in this range before it is visible to the human eye. Thermal infrared: Detects small temperature differences – e.g. warmer water is brighter than cooler land
Radar and microwave:
Useful in penetrating cloud cover and some vegetation to help map topography. It has also been used to map subtle geological features such as fault lines |
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Term
| Using Remote Sensing in GIS: |
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Definition
Remote sensing data is usually in raster format and can be incorporated into a GIS.
However Preparation and use of the data is a multi-stage process. That involves cleaning the data to remove noise, enhancing it, analyzing and classifying it and integrating it into GIS. |
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Term
| Stages to prepare remote Sensing Data: |
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Definition
First the sensor scans and records the image in raster format. >> Then the imagery requires preprocessing – this cleans the data by removing electronic noise and correcting mistakes such as missing scan lines. >>
Then the user enhances the data so better information can be obtained – eg improve visual contrast by changing subtle difference in gray tones into shades that are more distinctive. >>
Thematic analysis is next – involves turning enhanced data into selected themes – eg vegetation types, land use, etc. >>
Classification of themes into distinct categories is next – vegetation theme might contain categories of land cover – forest, grassland, agriculture, land, barren areas, etc. >>
At this stage the imagery is ready to go into the GIS for interpretation. |
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Term
|
Definition
| Global Positioning System. A network of satellites that continuously transmit coded information, which makes it possible to precisely identify locations on earth by measuring distance from the satellites |
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Term
|
Definition
GPS refers to a group of US Department of Defense satellites constantly circling the earth. The satellites transmit very low power radio signals allowing anyone with a GPS receiver to determine their location on earth
This system cost the US billions of dollars, as well as the cost of ongoing maintenance. |
|
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Term
| NAVSTAR system & its 3 segments: |
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Definition
Navigation Satellite Timing and Ranging, the official US Department of Defense name for GPS. 1)The space segment (the satellites) 2)
The control segment (the ground stations)
3) The user segment (you and your GPS) |
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Term
| The Space Segment of NAVSTAR |
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Definition
Consists of at least 24 satellites (21 active with 3 operating spares).
Satellites in “high orbit” about 12,000 miles above the earth surface. by being up so high, the signals cover a greater area.
The satellites are arranged so that any GPS receiver on earth can always receive from at least 4 of them at any time. You need at least 4 to get an accurate location. The satellites travel at speeds of 7,000mph which allows them to circle the earth once every 12 hours.
They are powered by solar energy.
They last for about 10 years but
have small rocket boosters to keep them flying in the correct path.
The first GPS satellite was launched in 1978. |
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Term
|
Definition
Each satellite transmits low power radio signal on several frequencies. The signal travels line of sight and passes through clouds, glass and plastic. Each satellite transmits a unique code to allow the GPS receiver to identify the signals.
The coded signals allow for calculating the travel time from the satellite to the GPS receiver on the Earth.
This travel time multiplied by the speed of light equals the satellite range. |
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Term
| Control Segment of the GPS: |
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Definition
| segment controls GPS satellites by tracking them and then providing them with corrected orbital and clock (time) information. There are 5 control stations located around the world. 4 unmanned receiving stations which constantly receive data from satellites and then send that information to the master control station. 1 master control station – corrects the satellite data and sends the information to the GPS satellites. |
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Term
|
Definition
| This is the person and the GPS unit. |
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Term
| Finding Location with a GPS |
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Definition
| The GPS receiver has to know WHERE the satellites are (location) and how FAR AWAY they are (distance). The GPS receiver picks up 2 kinds of information from the satellites. 1) Almanac data containing approximate positions of the satellites – this is continuously transmitted. 2)Ephemeris data – this is the corrected and exact position data which is valid for 4 to 6 hours. Time is also essential! **At least 4 satellites must be tracked and 4 fixes recomputed to correct for the travel delay and GPS receiver clock error. |
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Term
|
Definition
1)Ionosphere and troposphere delays - the satellite signal slows as it passes through the atmosphere. The system uses a built in model that calculates an average amount of delay
2)Signal multi-path error – this occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver – it increases the travel time of the signal
3) Receiver clock errors – the built in clocks in the GPS units have very slight timing errors
4) Orbital errors – also know as ephemeris errors – slight inaccuracies in the satellites reported location
5) Number of Satellites visible – the more the better the accuracy. The clearer the view the better the reception. Buildings, terrain, electronic interference, dense foliage can block signal reception and cause error. IONOSPHERE is the most important natural source of error. Finally, number 6 is Intentional degradation of the satellite signal – the US military intentionally degrades the signal in order to prevent military adversaries from using accurate GPS signals – this was turned off in May 2000 so accuracies are currently 6-12 meters. At the beginning of the Iraq war it was around 80 to 100 meters. |
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Term
|
Definition
| Differential GPS is a more accurate GPS system. It works by placing a GPS receiver at a known location nearby – the reference station. Since the reference station knows its exact location it can determine errors in the satellite signal and because it is closer it increases your accuracy. DGPS accuracy is 1-5 meters or even down to centimeters. |
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Term
| Importance of GPS in GIS: |
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Definition
| GPS has become a major component of GIS. GPS provides highly accurate positions anywhere on earth- this can be used to ground truth remote sensing data, allow for precise mapping, allow for field data collection, help with correction of maps, etc. |
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Term
| What Factors must be considered in Assessing the Data quality of your map? |
|
Definition
1) Error
2) Accuracy
3) Precision
4) Generalization
5) Scale errors
6) Incomplete area coverage
7) Smallest scale rule – determines the accuracy |
|
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Term
|
Definition
| the degree to which information on the map matches true or accepted values |
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Term
|
Definition
| the level of measurement and exactness of description. |
|
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Term
|
Definition
| refers to the relative accuracy and precision of a GIS database |
|
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Term
|
Definition
| encompasses imprecision and inaccuracies in the data |
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Term
| Important Sources of Error: |
|
Definition
Age of data,
Aerials cover,
Map scale,
Density of observations,
Relevance,
Format,
Accessibility is not equal (Data may not be as readily available for free in NZ), and
Cost (You are constrained by your budget ) |
|
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Term
| Propagation and Cascading |
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Definition
| one error leads to another. and errors propagate unchecked from layer to layer repeatedly. |
|
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Term
| Data accessibility and Cost |
|
Definition
Accessibility can be hampered by Issues of ownership – fear, large investment.
Global distribution – the haves and have nots. And
Copyright issues – sensitive information (don't let poachers know where sensitive species are). As for cost there are no established price lists for geographic data.
Ranges from free to very expensive. |
|
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Term
|
Definition
| The spatial data transfer standard was established in the 1990’s and many companies have adopted this standard. In New Zealand and Australia we use the ANZLIC standards. |
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Term
| What is Included in MetaData? |
|
Definition
Identification – title, area, dates.
Data quality – accuracy and precision, etc.
Spatial data organization – raster-vector, location.
Spatial reference – projection, grid system, datum, coordinate system.
Features and attributes – database content.
Distribution – how to obtain the data, contracts, fees, formats, etc.
Describe acronyms and column headings. |
|
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Term
| How can you extract features? |
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Definition
Attribute Query “Pop is < 1,000” or “State Capital”....
Or Select by location “Census Tracts that are within the city of New York” or “Industrial plants within a distance of 1 mile from rivers” |
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Term
| Geoprocessing tools do what? |
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Definition
| GIS operations manipulate data sets to produce new output day. Ex) Clip, Dissolve, Intersect, Union, Append |
|
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Term
| List the 6 basic Geoprocessing Tools: |
|
Definition
| Clip, Dissolve, Intersect, Union, Append, Erase |
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Term
|
Definition
| Similar to us a 'cookie cutter' to select features and make them into a new layer. Gives cleaner lines than select by location. This tool uses a polygon boundary to cut features and their attributes from a feature class. |
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Term
|
Definition
| Dissolve takes data and aggregates items that have the same value. aka makes states into regions. Can also aggregate statistics about those states (aka find pop. of the region) This tool combines like features based on a specified attribute or attributes. |
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Term
|
Definition
| Append connects features together. You get data separated by neighborhood and you want to go ahead and create town wide data. You append it. This tool merges multiple feature classes together to create a single feature class. |
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Term
|
Definition
| Union combines attribute data of the polygons in the two inputs and contains all the polygons from the inputs, whether or not they overlap. Contains all the attributes but broken up into more parts. (must be polygons) |
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Term
|
Definition
| Like Union but only keeps the overlapping parts. Has the combined attribute data of the features from the two inputs but only has the features that fall within the spatial extent of the overlayed polygons. (Can be all polygons, polygon/lines, polygons/point, or line/line. NOT line/point or point/point.) |
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Term
| What does Model Builder do? |
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Definition
| Automates and strings functions together. It can help you with complicated tooling. |
|
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Term
| What’s the difference between Extracting Features and Geoprocessing Tools? |
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Definition
| The first is Quick and Dirty while the second is More precision. |
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Term
| What are the main guidelines you should take into consideration when publishing your map? |
|
Definition
Colour,
Legend design,
Shape,
Texture,
Density,
Size,
Text. |
|
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Term
| What are the main guidelines you should take into consideration when publishing your map? |
|
Definition
Colour,
Legend design,
Shape,
Texture,
Density,
Size,
Text. |
|
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Term
|
Definition
| One of the most powerful ways to stretch the capabilities of GIS maps is taking advantage of the extraordinary ability of humans to use color information to aid in visualizing data. |
|
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Term
| What 3 basic dimensions of color do you need to understand? |
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Definition
| Hue(wavelength- red vs orange pure vs non-pure hue), Lightness(Shade where darker usual implies higher values) and Saturation (Pure, a saturated color only has one hue, red-grey vs RED). |
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Term
| How can we use the 3 basic dimensions to aid our maps? |
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Definition
| Using Pure Hues or well defined hues make the map easier to understand. Lightness levels can help people visualize rising or increasing values. Saturation is the least understood dimension, use it's powers sparingly. |
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Term
|
Definition
| Different shapes for different symbols leds you to assume they represent different kids on thing (major road vs not, capital vs not) |
|
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Term
|
Definition
| Texture can help distinguish between different types of areas. |
|
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Term
|
Definition
| The density of a texture can represent ordered data to a limited extent. |
|
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Term
|
Definition
Size is a very important visual variable for ordered data.
As in proportional symbol maps, the relative size of icons gives the viewer a qualitative estimate of the relationships of the attributes of the spatial units in the display. |
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Term
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Definition
Have it be compact and organized (group sim features together), self contained and large enough to be fully readable & Comparable to the actual map. Also Good title. Also Good to have:
DATE!!!
Creator,
Affiliation,
Data Source. |
|
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Term
| Use of Text on the Display: |
|
Definition
| Make sure the style, size, color, & placement are well done! |
|
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Term
|
Definition
| San Serif, Italic fonts are common for water features such as rivers and oceans, help represent the fluidity of these features. |
|
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Term
|
Definition
| Don't go smaller than 8pt. And variations need to be at least 25% larger. (10, 12.5, 16) |
|
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Term
| 11 Required Map Elements For Future Maps: |
|
Definition
1. Title
2. Scale
3. Legend
4. Location
5. Sources
6. Projection
7. Datum and spheroid specific to projection
8. Orientation – north arrow
9. Who prepared map
10.Who map was prepared for aka AUT GIS class
11. Date
Date |
|
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Term
| Advance spatial analysis. Difference between Overlay tools and single data layer tools? |
|
Definition
| 1. Intersect, Union, Identify and Clip. 2. Eliminate, Dissolve, Buffer. |
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Term
| What if we want to look at the relationships between themes that are in different layers? |
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Definition
| As long as these themes share a common co-ordinate system, they can be related together using Overlay Operations. However it is not possible to overlay points and lines. |
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Term
|
Definition
| very similar to clip, except that the input layer features that overlap with the ‘erase layer’ polygons are erased rather than preserved. Input layer features can be polygons, lines, or points; but ‘erase layer’ features must be polygons. (Output of same class as input) |
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Term
| More information on Dissolving: |
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Definition
| DISSOLVE is used to create a simplified layer from one which is more complex. While the input layer may contain information concerning many feature attributes, the output layer contains information about the dissolve item only. |
|
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Term
|
Definition
| Input layer features can be polygons, lines, points, or nodes. Buffering then creates buffer 'polygons' around specified input layer features. (Proximity or Distance based operation) |
|
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Term
| 3 Types of Buffer Operation: |
|
Definition
1. Simple- uses a single buffer distance for all buffer zones.
2. Incremental- is incremental buffers, used for looking at ‘distance-decay- functions
3. Constrained- The buffer stops wherever a predefined constraint is encountered. whether a slope or some other limiting function such road, unsuitable land use, stream or ocean barriers. |
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Term
|
Definition
Roads
Stream barriers
Unsuitable vegetation or land use types. |
|
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Term
| Which queries are faster in raster, which queries are faster in vector? |
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Definition
| multiple SPATIAL queries are faster in raster, but single ATTRIBUTE queries are faster in vector (especially if many questions are being asked at once)... |
|
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Term
| Breifly describe boolean logic: |
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Definition
| It is used to design queries by creating yes or no questions. It works differently in vector vs. raster. |
|
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Term
| Define a spatial vs an attribute query: |
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Definition
| A spatial query is asking what is there? while an attribute query is asking where is that? (Note: Complicated analysis will often require a mixture of spatial and attribute queries.) |
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Term
| What is the difference between single and multiple queries? |
|
Definition
Single queries ask questions about one data layer at a time.
Multiple queries ask questions about several data layers at a time. (multiple spatial queries can also involve asking about rain value at multiple spatial locations) (Single attribute queries ask about one attribute, multiple attribute queries involves questioning two or more attribute conditions that relate to more thane one set of spatial features. ) |
|
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Term
| Describe ways to conduct vector queries. |
|
Definition
For single spatial analysis you can use the identify button. You can also select the feature by clicking on it. This feature can then be the subject of analysis or exported as a new shapefile.
When working with two layers you can use select by location to select features in one layer based on their relationship to features in another layer. |
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Term
| So, how do you actually do a query in GIS for raster data? |
|
Definition
| How you do the query depends on the kind of query you want to do. The easiest type of query in raster is a single spatial query. In this case, all you have to do is click on the feature of interest (where) and your GIS will tell you the value of its attributes (what). You can use the identity tool. |
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Term
| Another way to do raster queries is to use the spatial analyst toolbar. Which can be found in two locations? |
|
Definition
1. Using the spatial analysis toolbar.
2.Found in the spatial analysis -> math section of the tool box. |
|
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Term
| How do you do an attribute query in raster? |
|
Definition
| Essential you must specify your question using GIS boolean logic. GIS checks the cells to see if the question is true or false making a new raster data layer based on the answers. 1 for true, 0 for class. Thus the grid is reclassified. 1. Go to spatial analyst toolbox ‘reclassify’. 2. Set True 1, False 0. So say you want to find elevations above 300 you go would set the old values of 1 to 300 to 0 and the old values of 300 to 1000 1 and then all elevation above 300 will be marked with 1 as in true and others 0 as in false. Or go to spatial analysis toolbar raster calculator [Elevation] > 3000 which will do the same thing ( 1 to 300 being 0 and 300+ being 1). |
|
|
Term
| How do you do multiple queries in raster? |
|
Definition
| You must use Map algebra to compare features between data layers using overlay techniques. |
|
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Term
| What is required to do raster overlay? |
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Definition
| A raster overlay which compares the data values at each cell for various laters and produces the results requires certain consistencies in the layers. the size and number of grid cells in each data layer must be the same. Also, each data layer must cover the same area on the earth (have the same map extent). And, of course, all the grids must be referenced to the same datum, map projection and resultant coordinate system to ensure that the grids line up and that the results make sense. |
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Term
| How do you use OR and AND in Map Algebra? |
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Definition
| 1st + 2nd = boolean OR while 1st x 2nd = boolean AND. AND can also be acheived by using the minimum tool which picks the minimum number for each cell between both layers. OR you end up with 1 or 2 being true. |
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|
Term
| The efficiency of map algebra to add, multiple, subtract, ect layers form each other is the primary reason why doing multiple spatial queries is faster in raster. |
|
Definition
|
|
Term
| What are Cartographic models? |
|
Definition
| A step-by-step flow chart used to graphically represent the GIS data and procedures performed in a GIS based study |
|
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Term
| What are the benefits of using a Cartographic model? |
|
Definition
| Organize the procedures, Identify data required, Problem solving - identify why & in which steps problems occur, and Valuable source of reference and documentation for your metadata. |
|
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Term
| How do you use design a cartographic model? |
|
Definition
| Work backwards in order to achieve the best possible final product. Don’t let the exist data control your output. Start with the final product and find out what data you need how you can get that from the existing data. Use different symbols for different data types, indictate GIS operations and connect symbols with arrows. |
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Term
|
Definition
| A problem in a computer program, an inadvertent error that can usually be fixed. In your case likely a human error in how you are trying to use the software. |
|
|
Term
| What are the four main type of errors that you can encounter? |
|
Definition
| Network/hardware, syntax, data and logic. |
|
|
Term
| Define Hardware errors and how to correct them: |
|
Definition
| Hardware errors occur when there is a problem at a layer of programming below where your GIS operates. The error messages from these type of errors typically make the least sense because they are the farthest removed from how you are thinking about what you are doing. AND they don’t necessarily indicate that you’ve done something wrong. An overloaded computer, or one low on space, starts acting very strangely. That’s why these are often termed WEIRD, GLITCHY ERRORS and have prompted yet another golden rule of GIS: when in doubt, REBOOT! |
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Term
|
Definition
| Syntax errors are the simplest type of errors in your analysis and result from incorrectly specified SYNTAX (the rules for writing a command). Likely something was spelled wrong, an option was forgotten or done incorrectly or the file name was too long. (Don’t use gaps, special characters or names >12 digits. ) |
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Term
|
Definition
Data errors are more complicated and tricky than syntax errors. In this case you have the right command options and everything is spelled correctly, but there are problems with the data itself, such as indicated below (using the wrong data, mistake in an earlier step, using units that don’t match the data or using the wrong type of data for what you want to do).
Check to make sure you are using the right data, the units and coordinate system are correct, check the meta data and then if you can’t find a problem backwards looking at previous steps until you find the error. Prevention by checking the outputs at each stage can help prevent you have to work backwards! |
|
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Term
|
Definition
| Logic errors are the trickiest of all errors because these errors are not noticed by the GIS software and will not result in an error message. With logic errors, the commands you run work perfectly, but the resulting images don’t make any sense when considered in light of the original questions you wanted to answer. To identify these errors requires thinking logically about what you are trying to do and why. It may be that you are asked to do a GIS project where the instructions you are given contain logic errors - it is up to you to determine this, and sort it out with your client. If you identify any of these in your team project, make sure to note them in the sources of error section of your final report. to help identify logic errors: Think about the question you are trying to answer, what the final product should look like and what your results look like and check your decision rules looking for possible errors. |
|
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Term
|
Definition
| However, unlike other simple graphic data structures, shapefile polygons are represented by one or more rings. A ring is a closed, non-self-intersecting loop. This structure can represent complex structures, such as polygons, that contain "islands." The vertices of a ring maintain a consistent, clockwise order so that the area to the right, as one "walks" along the ring boundary, is inside the polygon, and the area to the left is outside the polygon |
|
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Term
|
Definition
| A primary advantage of shapefiles is that this simple file structure draws faster than a coverage does. This may be why the shapefile data structure was developed for ArcView GIS, a software program that was originally designed for data viewing rather than analysis. In addition, shapefiles can easily be copied and do not require importing or exporting as do .e00 format files. The shapefile specification is readily available, and a number of other software packages support it. These reasons have contributed to the emergence of the shapefile as a leading GIS data transfer standard. |
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Term
|
Definition
| - Must be done in an editing session. Can combine selected features within a layer. Combines input features from multiple input sources (of the same data type) into a single, new, output feature class. The input data sources may be point, line, or polygon feature class or table. |
|
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Term
|
Definition
| A database or tabular file containing information about a set of geographic features, usually arranged so that each row represents a feature and each column represents one feature attribute. |
|
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Term
|
Definition
| The operation of relating and physically merging two attribute tables using their common item. |
|
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Term
|
Definition
| Creates a table join in which fields from one layer's attribute table are appended to another layer's attribute table based on the relative locations of the features in the two layers. Data tables to a shapefile? |
|
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Term
|
Definition
| The ModelBuilder interface provides a graphic modeling framework for designing and implementing geoprocessing models that can include tools, scripts, and data. |
|
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Term
|
Definition
| A reference framework consisting of a set of points, lines, and/or surfaces, and a set of rules, used to define the positions of points in space in either two or three dimensions. |
|
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Term
|
Definition
Breaks the Input Features into multiple output feature classes.
The boundary of each unique value in the Split Field is used to split the Input Features. Splitter must be polygon. |
|
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Term
|
Definition
| - Used to perform queries for raster. Using Boolean Logic. |
|
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Term
|
Definition
| The use of Geoprocessing Tools to manipulate data inputs and product outputs. |
|
|
Term
| What are some examples of spatial analysis overlays? |
|
Definition
|
|
