1. Spatial Analysis in R Points, lines, polygons, & raster! 06/16/2016
GUND institute for Ecological Economics
University of Vermont
Insu Koh

2. Review Read spatial data Check projection:
Reproject raster data
Three options!
projectRaster( …, method= ‘bilinear‘ or ‘ngb’)
for DEM data: ‘bilinear‘
for NLCD data: ‘ngb’
Additional work for NCDL data
Check DBF file
Check legend slot in raster layer
Overlay data set
Make legend!
ArcGIS

3. Google map in R library(dismo) Additional material:
gmap: download base google map
Google Earth is in a geographic coordinate system with the wgs84 datum. (EPSG: 4326)
+init=epsg:4326
+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs
Google Map is in a projected (Mercator) coordinated system that is based on the wgs84 datum. (EPSG: 3857)
SR-ORG:7483 = EPSG: WGS84 Web Mercator
+init=epsg:3857
+proj=merc +a= b= lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +wktext +no_defs
Additional material:

4. Google map in R library(googleVis)
Plotting point data on a google map web
gvisMap
gvisGeoMap

5. Point
1. Create spatial data from GPS information 2. Calculate distance among points: Euclidean distance, Great Circle distance. 3. Sample points randomly spsample() : sample types: random, stratified, … spsample set.seed(): define your random number then keep return same result! 4. Make buffer: use gBuffer{rgeos} 5. Subset & query point data same as subseting dataframe in R
Bivand et al P. 35

6. Line Polygon Zonal statistics: how many points are in each polygon?
Create lines
Make buffer
Distance from point to lines
Polygon
Assessing coordinate information
Bivand et al P. 40
Zonal statistics: how many points are in each polygon?

7. Raster Class: extent, resolution, projection.
Basic functions in raster packages
Create your own raster
Get or assign the value
Crop raster boundary
[1,1] or [1]
[1,10] or [10]
[?,?] or [?]
[10,10] or [100]
newr = raster(nrows=10, ncols=10)
values(newr) = 1:ncell(newr)

8. Raster RasterStack and the RasterBrick Raster algebra
The principal difference between these two classes is that a RasterBrick can only be linked to a single (multi-layer) file. In contrast, a RasterStack can be formed from separate files and/or from a few layers (’bands’) from a single file.
Raster algebra
Math
Aggregation/moving window
Overlay
Reclassification
Zonal statistic .