Unit Nine: Georeferenced Unit Nine: Georeferenced Data Data In this unit… In this unit… Data Supported by ArcGIS Data Supported by ArcGIS Geodesy Geodesy Datum Datum Coordinate Systems Coordinate Systems Projections Projections ArcGIS and Projections ArcGIS and Projections ArcCatalog ArcCatalog
Unit Nine: Georeferenced Data. Data Supported by ArcGIS Geodesy Datum Coordinate Systems Projections ArcGIS and Projections ArcCatalog. In this unit…. Review. GIS’ depict reality only approximately! Required: Reality A model A referencing system - PowerPoint PPT Presentation
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Unit Nine: Georeferenced Unit Nine: Georeferenced DataData
4.4. Methods for referencing data Methods for referencing data within the referencing systemwithin the referencing system
3Unit Nine – Georeferenced DataUnit Nine – Georeferenced Data
Data Supported by ArcGISData Supported by ArcGIS
► Several types of data are Several types of data are supported by ArcGISsupported by ArcGIS ShapefileShapefile
ArcInfo CoverageArcInfo Coverage
GeodatabaseGeodatabase
CADCAD
GRID & TINGRID & TIN
► ArcGIS uses icons to differentiate.ArcGIS uses icons to differentiate.
4Unit Nine – Georeferenced DataUnit Nine – Georeferenced Data
Data Supported by ArcGISData Supported by ArcGIS
► Some data is of a complex Some data is of a complex structure:structure: Coverages ‘expand’Coverages ‘expand’
Layers Layers are are
‘inside’‘inside’
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Data Supported by ArcGISData Supported by ArcGIS
► Geodatabases can:Geodatabases can:
1.1. Store all other types of dataStore all other types of data
2.2. Have “Rules”Have “Rules”
3.3. Support Support Data modelsData models
4.4. Be stored in MS AccessBe stored in MS Access
5.5. Create hierarchical structure of Create hierarchical structure of relationships relationships (data sets and data classes)(data sets and data classes)
ggeodatabaseeodatabase
coveragecoverage
shapefileshapefile
……or a or a reallyreally complex structure complex structure
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Spatial ReferenceSpatial Reference
1.1. DATUMDATUM
2.2. PROJECTIONPROJECTION
3.3. COORDINATE SYSTEMCOORDINATE SYSTEM
4.4. MAP UNITSMAP UNITS
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Ellipsoid SizeEllipsoid SizeEllipsoid ShapeEllipsoid ShapeLocation of ellipsoidLocation of ellipsoid (relative to Earth)
DatumDatumis is
defineddefinedby...by...
Datum
A “Model” Starting Place
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Datum
History
LumpyLumpyPotatoPotato
Sphere
Ellipse
Our idea of the earth’s shape evolved…
Our idea of the earth’s shape evolved…
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Datum
Common Datum(s?)
NAD - 83 (North American Datum - 1983)based on GRS-80 ellipsoid
NAD - 27 based on Clarke 1866 ellipsoid
WGS -84 (World Geodetic System - 1984)based on ellipsoid very similar to GRS-80
GPS
USGS
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Projection
The Basic Idea
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.
12Unit Nine – Georeferenced DataUnit Nine – Georeferenced Data
Projection
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Coordinates & Map Units:
A Reference Grid
Planar Coordinates
coordinates arecoordinates are
NH State PlaneNH State Planemap units aremap units are