1. Learn R! GIS

2. What is GIS? GIS = “Geographic Information System” Ideally In practice
Answer questions related to proximity
In practice
A method of job security
A method of intimidation
A method of making money
Tools better understood than ideas behind them

3. Disclaimer: Why I don't use ArcGIS
QGIS is a free replacement with better features
Faster than ArcGIS to an order of 10x
ArcGIS is a pain to install/set up licenses
Useless for Linux/Mac users
ArcGIS expense limits use: government/industry/universities
ESRI spends $$$ promoting and “locking in” ArcGIS users
Point-and-click is nice for making maps, but “toolbox” style analysis is painful for reproducible/dynamic work

4. ESRI's Legacy: “Shapefile” Format
Most common GIS data format (90's relic)
Information stored across many files
.shp geometry feature information (i.e. counties)
.shx index of features
.dbf attributes of each geometry (i.e. population)
Sometimes also
.prj projection information
.shp.xml metadata
Imagine if Word docs were split into 5 files!

5. Geometry features (.shp)
Actually just a list of coordinate sets
Software connects each set into a polygon
(1,3)
X Y
0 0
0 2
1 3
2 2
(0,2)
(2,2)
(0,0)

6. Geometry projection (.prj)
The earth isn't flat, but maps are!
Are my points GPS coordinates, or what?
TWO Basic Types:
Geographic (“GPS”)
Latitude/longitude
Pseudo-spherical
Projected (“Survey”)
Feet/meters
Rectangular

7. Geometry attributes (.dbf)
Really just a dataset
Contains one row per polygon in dataset
ID Area Toxins Cases

8. GIS Junk (but don't delete!)
Shapefile index (.shx)
Helps ArcGIS go faster (but still slower than QGIS)
Metadata (.shp.xml)
Data source, notes, etc.
Other things in the (.shp)
Presence of holes
Bounding box
Shape type (point, line, polygon)

9. The sp package in R Packs GIS data into an addressable object
You can also use [ ] notation to subset
SpatialPointsDataFrame @ @ @
proj4string
polygons
data
bbox $ $
plotOrder
var1
var2

10. Working with spatial data
With rgeos and rgdal installed, common data commands will be intuitively translated!
plot(myshape)
myshape$var1
myshape[1:2,]
myshape[myshape$var1==FALSE,]
Sp objects work like any other object:
mile3 <- gbuffer(myshape,3*5280)
cents <- gcentroid(myshape)

11. Caveat: Don't use merge()!
Sometimes need to link attribute/shape data
US Census Data
TIGER Line Files
Don't use merge()! Looks good but doesn't work
This re-orders the data, but NOT the shapes!
Instead, re-order the new data & append to old
Example in lab

12. Lab Import an ESRI shapefile (w/built-in data) Basic maps with plot()
Link attribute data to spatial data
Write to .kml so you can show your maps on Google Earth (good for interactivity).
Examples of working with Google Earth/QGIS