Review of Key Geographic Concepts Review of Key Geographic Concepts and Principals and Principals

Nancy Lemay, University of Ottawa

Barbara Znamirowski, Trent University

Jenny Marvin, Guelph University

2006 Ontario DLI training2006 Ontario DLI training

Presentation OutlinePresentation Outline

• Defining certain concepts and terms: Map scales, coordinate systems, datum and projections.

• ArcGIS Desktop software collection: ArcReader, ArcView, ArcEditor and ArcInfo.

• Review of the Main Features of ArcGIS 9.0 : ArcMap, ArcCatalogue and ArcToolbox.

Map ScalesMap Scales• A defined dimensional relationship between reality and

the map (Robinson et al., 1995).

• Scale is “unitless” because it is a ratio.

Small scale: 1:250,000

Large scale: 1:50,000

Map Scales (cont’d)Map Scales (cont’d)

Maps are made to scale. In each case, the scale represents the ratio of a distance on the map to the actual distance on the ground. For example, if 2 cm on a map ...

represents 1 km on the ground ...

the scale would be 2 cm = 1 km, or...

Co-ordinate SystemCo-ordinate System

A co-ordinate is a reference system based on mathematical rules for specifying positions ( locations) on the surface of the earth.The co-ordinate values can be spherical ( latitude and longitude) or planar ( such as the Universal Transverse Mercator)

Types of Coordinate SystemsTypes of Coordinate Systems

– Geographic coordinate system:– Uses latitude and longitude for locating

positions on the uniformly curved surface of the earth.

– Rectangular/plane coordinate systems:– Used to locate positions on a flat map.

– For example: Lambert Conformal Conic

ExampleExample

• Let’s project a “shapefile” of Canada….

Unprojected versus ProjectedUnprojected versus Projected

Projected

Unprojected

Geographic Coordinate SystemGeographic Coordinate System• The Equator (latitude) and Prime Meridian (longitude) are the

reference points.

• The Cartographic Boundary Files, the Road Network Files are disseminated in latitude/longitude coordinates.

Prime meridian

Equator

Datum: A Datum is a geodetic reference point that specifies the size and shape of the earth, and the base point from which the latitude and longitude of all other points on the earth’s surface are referenced

DatumDatum• Geodetic reference system that specifies the size and shape of the

earth. Types of datums: (1) Earth-centered (WGS84, NAD83), (2) Local (NAD27, ED50).

• The spatial data disseminated for the 2001 Census are based on the North American Datum of 1983 (NAD83).

http://www.geod.nrcan.gc.ca/index_e/geodesy_e/reference04_e.html

Example: NAD27 vs NAD83Example: NAD27 vs NAD83

Different File FormatsDifferent File Formats

Shapefile “.shp” is used in ArcGIS and is accompanied by the following auxiliary files:

• “.dbf” the dBASE file that stores the attribute information of features. Required.

• “.shx” the file that stores the index of the feature geometry. • “.sbn & .sbx” the files that store the spatial index of the features. • “.prj” - the file that stores the coordinate system information.• “.xml” - metadata for ArcInfo 8.0, for using shapefiles on the

Internet.

Coverages are often published in a compacted form with the extension “.e00”:

• Proprietary file format used to distribute Arc/Info datasets. Topology and attributes are properly maintained in this format.

ExampleExample

• Let’s import a “.e00” file….

• For instructions on how to import an .e00 file: http://www2.lib.uoguelph.ca/resources/gis/HELP/e00.cfm

ArcGIS Desktop software collectionArcGIS Desktop software collection

ArcGIS Desktop

ArcReader ArcView ArcEditor ArcInfo

Free viewer to view, print and query maps.

Extensive mapping, data use, and analysis along with simple editing and geoprocessing capabilities.

Advanced editing for shapefiles and geodatabases in addition to the full functionality of ArcView.

Extends the functionality of both ArcView and ArcEditor.

Main Features of ArcGIS 9.0*Main Features of ArcGIS 9.0*

• ArcCatalog:– To access and manage geographic data.  Data can be copied, moved,

deleted, and viewed before it is added to a map.  In addition, metadata can be either read or created in FGDC or ISo19115 format.

• ArcMap:– To display and query maps, create hardcopy maps and perform spatial

analysis tasks.

• ArcToolbox:– An environment for performing geoprocessing operations (i.e., operations

that involve alteration or information extraction). ArcToolbox is embedded in both ArcCatalog and ArcMap.

*http://libinfo.uark.edu/gis/tutorial_sec1.asp

ArcCatalogArcCatalog

Help with ArcGISHelp with ArcGIS

• http://webhelp.esri.com/arcgisdesktop/9.1/index.cfm?TopicName=welcome