1. Introduction to Cartography GEOG 2016 E
Lecture-7
Geographical Information System

2. What is GIS? GIS is a system for capturing, storing, retrieving,
analyzing and
displaying
geographic data.

3. GIS Concept
Use databases to keep spatial data and their attributes so that analyses could be performed.
ESRI 2004

4. GIS Software Personal Computer Workstation Mainly Vector-Based ArcGIS
ArcView
GeoMedia
MapInfo
PAMAP/TerraSoft
ArcInfo
Intergraph
Microstation
GRASS
Mainly Raster-Based
IDRISI
ERDAS Imagine
ENVI

5. ArcGIS Developed by ESRI (Environmental Systems Research Institute).
Components: ArcMap, ArcScene, ArcCatalog, ArcInfo

6. MapInfo
Developed by MapInfo Corporation.

7. GRASS
Open-source software.

8. Spatial Data Structures in GIS
Raster
Points
Lines
Polygons
Surfaces
Vector
Points
Lines
Polygons

9. Data Structures – Points
Examples
Owl locations
Wildlife observations
Inventory plot locations
Homes
Archeological features

10. Data Structures – Lines
Examples
Roads
Streams
Contour lines
Logging trails / corridors
Cruise lines
Trails

11. Data Structures – Polygons
Examples
Stands (management units)
Soils
Ownership boundaries
Lakes

12. Vector Data Structures
Points
Lines
Polygons

13. Vector Data Structures Advantages and Disadvantages
Highly precise.
Compact data structure. Requires less storage space in computer memory.
Closely approximates hand-drawn maps.
Disadvantages
More complex than raster data structure.
Overlay operations are more difficult to process.
Representing a high-level of spatial variation is difficult.

14. Raster Data Structures

15. Raster Data Structures – Grid Cells
Examples
Spectral reflectance (image)
Other EM radiation (thermal)
Classified data
Rasterized vector data
Digital elevation models
Scanned data

16. Raster Data Structures Linear Features
Raster representation of linear features has inherent error.

17. Raster Data Structures Advantages and Disadvantages
Simple data structure.
Computationally efficient.
Overlay operations are easy to process.
Representing a high-level of spatial variation is easy.
Disadvantages
Topological relationships are difficult to understand.
Less compact – requires large storage space.
Display may not be visually appealing.

18. GIS Databases General Characteristics
Includes one spatial data structure (point, line, polygon, raster).
Includes one thematic description.
Includes an attribute table.
A large GIS database may be a combination of several smaller databases.
May or may not include metadata.

19. Metadata A description of an accompanying spatial data file.
Should include information about:
When created
Who created
Minimum Mapping Unit (MMU)
Projection / Datum / Coordinate system
Attribute information
Accuracy Assessment
Maintenance policy
Source location
Copyright information
Contact

20. GIS Database Errors
These errors can occur in GIS databases of either data structure (vector or raster):
1) Positional errors - coordinates of a map feature differ from their true locations
2) Boundary errors - uncertainty in the location of edges of features
3) Classification errors - features are not identified correctly

21. Positional Errors
Property boundary
Roads v. Digital Orthophotograph

22. Boundary Errors
Fuzzy boundaries (stands)

23. Classification Errors
Typing errors (recent harvest)
Vegetation classification (incorrect vegetation type)
Remember: All image classifications have error.

24. GIS Terminologies Coverage Shapefile DEM TIN A GIS layer.
Digital file format of ESRI’s ArcView software.
DEM
Digital Elevation Model in raster data format.
TIN
Digital Elevation Model in vector data format.