1. GIS concepts, skills and tools
Midterm Review
GIS concepts, skills and tools

2. A GIS is a tool for making and using spatial data
Cartography
Data Processing & Analysis

3. Functions Supported by GIS Software

4. Today’s Overview: Earth Model and Projections Cartography
Spatial Analysis
Software and File Structure

5. Modeling the Earth: Describing the Ellipsoid: • Flattening:
f = (semimajor-semiminor) / semimajor
• Value often given inversely: 1/f

6. Ellipsoids Approximate the Geoid
Why an Ellipse still isn’t perfect…
Earth’s Geoid

7. Add coordinates to ellipse to get a datum
NAD83
NAD87
WGS84

8. Ways of Measuring Position on Earth

9. Geographic Coordinate System!
Taking Spherical Coordinates and plotting them in X Y:

10. General Types of Projections
These different methods
of projection lead to
different map perspectives
and different areas of distortion

11. Example: Cylindrical Projections
This projection is how the
well-known (much to the
disappointment of many)
Mercator map is created.
UTM maps
are common!

12. Why are Projections in ArcGIS Important?
Three Spatial Orientation Situations:
data has no coordinate system – project
data has mismatching coordiante system – reproject
project “on the fly”
- Projecting data creates a new feature class
- Think about editing!

13. Cartography: Representing Data Well
Symbology
Color Ramps
Examples for Point Features:
Certain color ramps work with certain map types

14. Binning Data Where should the data be split? Possible Options: Manual
Natural Breaks
Equal Interval
search “Data Classification”

15. Elements of a good map: The 5 Ds: DOGSTAILS
Design, Density, Description, Distance, Direction
DOGSTAILS
D Date When the map was made
O Orientation Directions (north arrow)
G Grid Locates places on the map
S Scale What the map distance is
T Title What, where, and when
A Author Who made the map
I Index Map address of places
L Legend What the symbols mean
S Sources Basis for map information

16. Spatial Analysis - Spatial Data Model
GIS is a simplified
version of reality
Definition: Objects in a spatial database
plus the relationships between them

17. In GIS, data holds the answers to:
Where?
Location of features
What?
Properties and attributes of features

18. Main data model types Calculations Spatial selection Imagery…
Spatial selection
Cartography …

19. The Roles of Raster v. Vector Data

20. Different data examples we’ve used:

21. Skill List Selection & Geoprocessing
Raster manipulations – reclassification, calculations, etc.
DEM modeling – slope, flow, etc.
Statistics
Interpolation
Editing - Hand digitizing, attribute data entry
Georeferencing
Clear Symbolization
Conversion – moving data between formats

22. Common Geoprocessing Operations
Querying
Example of a spatial operation:
SQL language:
Selecting data subsets
Spatial Operations
Buffer
Clip
Intersect
Union
Merge
Dissolve

23. Raster Calculations
Math
Conditional Statements
Reclassification

24. Using rasters for analysis…
Zonal Statisitics

25. Flow Direction on a Raster:
The Hydrology Toolbox
let us model flow in the
Boulder Creek watershed

26. Editing How we change data: Projections Vector data editing
Geoprocessing
Hand digitizing
Attribute table
Raster adjustments
Calculations
Classification
Deletion of classes
Resampling

27. Georeferencing
World Files
Create one …
Export one…

28. We use different Arc software for different functions
Software Structure
File and data management
Interactive space
Cartography and spatial processing
3D visuals
We use different Arc software for different functions

29. ArcGIS Toolbox – what we’ve used (via the red box interface)
Buffer
Clip
Intersect
Union
Merge
Dissolve
Geoprocessing menu

30. ArcGIS Toolbox – More of what we’ve used

31. 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)
Sometimes writing to a
Geodatabase works better!