An overview of GIS data

1. An overview of GIS data

2. Today’s Topic: • GIS Data Models • Data Types • ArcGIS terminology • Review of coordinate systems

3. 2 basic types of Data Models • Raster • Vector 2 Kinds of GISs • Raster GIS • Vector GIS

4. Pixel Raster Raster GIS • Raster is nothing but an array of grid cells • Each cell is called Pixel (Picture element) • Example: IDRISI, ERDAS, GRASS

5. 400 450 500 600 600 300 350 450 400 450 250 200 150 150 400 0 50 100 250 450 DEM (Digital Elevation Model):An example of Raster Data

6. Raster representation of reservoir and highway

7. Raster GIS • In Raster, each cell is homogeneous • It represents either one class or another, nothing in between • However, in reality, a cell is not one thing or another.

8. Rasterizing of features Pixel Mixel

9. Raster Data • Raster is good for Continuous Data • Continuous Data: When data varies smoothly across the area. Ex: elevation, precipitation, etc. • Raster model provides the best representation for continuously changing data

10. Vector Data • Vector is good for Discrete Data • Discrete Data: When data value remain same for an area and then abruptly changes to another value. • Ex: landuse, soils, etc.

11. VectorGIS Vector GIS is based on POINTS LINES & POLYGONS Example: ArcView, ArcGIS, Manifold, etc.

12. Points Lines In the vector world everything is a point, a line, or a polygon Polygons

13. Vector representation of reservoir and highway

14. GIS Data Most of the available GIS data have been developed using ARC/INFO • Arc/INFO was a flagship product from ESRI • It was widely used all over the world

15. Software Year Data Format 1980’s Coverage Arc/Info 1990’s ArcView Shapefile 2000’s Geodatabase Geodatabase ArcGIS 8 & 9 ArcGIS 10 Brief history of ESRI’s GIS software evolution 2010

16. Spatial Data Format • Shapefile • Raster • Coverage • CAD • Geodatabase • Tables ArcGIS can work with spatial data in multiple formats

17. Coverages Shapefiles Common data formats Geodatabase

18. Shapefiles in Windows Explorer Shapefiles in ArcCatalog Shapefiles A shapefile consists of multiple files, and the common ones are *.dbf, *. shp, *.shx

19. 2 types of Geodatabase • File geodatabase (soils.gdb-newer type) • Personal geodatabase (soils.mdb-older type)

20. Feature dataset Feature classes What can be in a Geodatabase • Feature datasets - Collection of related feature classes • Feature classes • Tables • Annotations • Rasters

21. Why Geodatabase? 33% 66% • It is not only a container of different types of data but also provide enhanced functionalities • Domains • Rules (split and merge policies) • Topological association

22. Other types of data Tables Layer file • Does not contain data • But stores the symbology

23. Layer and Layer file? • A layer represents geographic data displayed in ArcMap • A layer references the data on a disk and keep it in memory rather than storing the data • A layer is created when you add a dataset to ArcMap

24. Layer and Layer file? • Layer is drawn with a default set of drawing properties (symbology) • Layer can be saved to a file as a layer file (.lyr) to store the symbology and shared with others

25. Map Documents 1.When you save a map in ArcMap, it will be saved as a file on disk called map document (.mxd) 2. Map documents (.mxd) do not store the data in it except the link to the data source 3. Map documents make it easy to save, reuse, and share your work in ArcMap

26. More on data • GIS data may be projected or unprojected • Projected or unprojected, GIS data is usually attached to a coordinate system • How do you determine the coordinate system of your data?

27. Two types of coordinate systems • Geographic coordinates: • Unprojected • Map units are in decimal degrees • Projected coordinates: • Data is projected • Map units are in feet or meters

28. Projected or Unprojected ?

29. Projected/Unprojected?

30. Projected Coordinate Systems (SPC)

31. How do you know the UTM zone of a place?

32. ?