Different kinds of data Example of Elevation Topographic DEM (Digital Elevation Model)

How can elevation be represented in a GIS?

GIS Data Specifics Getting into the guts of GIS data structure …

Basic structure of Vector and Raster: Points Lines Polygons Attributes Grid cells

Remember the idea of a Data Model: Keep the concept of data compression and machine code in mind…

The Roles of Raster v. Vector Data

Going Back to Elevation… Cartography Precision (?) of isolines Calculations Triangular Irregular Network Data compression

Converting from vector to raster

Converting from raster to vector

Editing! Yes, you can change data, but do it very VERY carefully! Vector data editing Geoprocessing Hand digitizing Attribute table Raster adjustments Calculations Classification Deletion of classes Resampling Always work in a disposable data copy and save Save SAVE!

Hand digitizing For example: Creating vector feature classes based off aerial imagery

Snapping

What this looks like in ArcMap: Warning: Opening an editing session in ArcMap changes how your.mxd functions! Feature being edited appears with green box vertices:

Topology Topology: The study of geometric properties that do not change as the forms are bent, stretched or undergo similar transformations

Issues with editing – topology rule fixes Slivers!

Vector feature topology and tables These tables allow for fast indexing and searching!

Network example for vector data: NHD (National Hydrography Dataset) Nodes Stream Order Modeling Flow

Direct editing of raster data is limited… The “Delete Selected” button is what you can use to edit in a raster table

… instead, change rasters with processing!

More Raster Processing Resampling Classification

Raster Compression Examples Run-length coding Quad-tree compression

Working with vector data attribute tables Edit attributes directly Hand editing in vector data attribute tables is possible Joins and Relates – a powerful technique! (Excel is useful here)

Join Types: One to One One to Many

Managing Data DBMS: Database Management System Control points for editing Potential conflicts Our shapefiles Not centralized

Shapefiles <> File Geodatabase spatial index format (.sbx) attribute format (.dbf) projection format (.prj) spatial index format (.sbn) shape format (.shp) shape index format (.shx) geospatial metadata (.xml)

For Further Reference! Author: Paul Bolstad