1. Introduction to GIS

2. What is GIS? Stands for “Geographic Information System”
For display and analysis of geographic information with computers
Also known as “computer mapping”

3. Types of GIS Symbols Points Lines Polygons Images
Type Symbol Example
Points
Lines
Polygons
Images
Towns, points of interest, campgrounds,…
Rivers, roads, railroads,…
States, countries, boroughs,…
Satellite image, topographic map, shaded relief,…
Image source: MapTEACH

4. Themes and Layers GIS organizes information into layers
Layers represent different “themes”
A GIS map may have one or more layers
Roads
Villages
Rivers
Airports
Vegetation
Image source: MapTEACH

5. Example Thematic Maps National Parks Sedimentary Basins Topography
Museum Locations
Image sources:

6. How is GIS Used? Navigation Emergency response
Natural resource management
Military
Business analysis
Education
And many more…
Image sources:

7. Why use a GIS? GIS maps are dynamic (can be changed).
Any information that has a location component can be mapped.
A GIS anchors information to its real-world location on a map.
We can display, measure, and compare features.

8. From Sphere to Flat Map The Earth is a slightly squished sphere
We can describe any location with degrees of Longitude: vertical lines W   E of zero (prime meridian) Latitude: horizontal parallel lines N ↕ S of zero (equator)
A globe is a model of the Earth
Image sources:

9. From Sphere to Flat Map For Alaska, the most common datums are:
One simple way is to make a grid of latitude and longitude.
Then you can plot locations like x and y on graph paper.
This is called the “geographic coordinate system.”
The coordinate system is based on an approximation of the shape of the Earth (or “datum”).
Since the Earth is irregular, the surface is changing (continental drift), and we have gotten better at measuring it.
There are many “datums” to go with the geographic coordinate system.
For Alaska, the most common datums are:
WGS84 (World Geodetic System 1984)
NAD83 (North American Datum 1983)
NAD27 (North American Datum 1927)
Image source: MapTEACH

10. Why Make a Flat Map?
The globe doesn’t fit in my desk drawer or my pocket.
The globe doesn’t work very well for mapping detail.
It is hard to measure distances and areas on a curved surface.
So what do we do?
Get the computer to “project” the map with mathematics.
Image source: and

11. Which Projection? There are many,many projections to choose from.
Most common types are:
Cylindrical
Conic
Planar
Transverse Cylindrical
Each projection distorts
Your choice depends:
on the theme or purpose of your map
the scale (large or small detail)
the location of the area on the Earth a. b. c. d.
Image source:

12. Which Projection? For Alaska, we use two basic types:
For Statewide small-scale data: “Albers Equal Area Conic - Alaska”
For Local large-scale data: “Universal Transverse Mercator” (UTM)
Image source: MapTEACH

13. Types of GIS Files Points Lines Polygons Images
Type Symbol Example
Points
Lines
Polygons
Images
“Vectors” (shapefiles, .shp, .dbf, shx, …)
Towns, points of interest, campgrounds,…
Rivers, roads, railroads,…
States, countries, boroughs,…
Satellite image, topographic map, shaded relief,…
“Raster files or image files” (.jpg, .gif, .tif, .png, .bmp, …)
Image source: MapTEACH