Basic GIS in R
in R / Software on Code, Example, Gis, R, Software
Recently I had to help out a colleague with processing some spatial data in R. The overall goal was to find landscape parameters (topography, soil characteristics, etc.) within the neighbourhood of a flux tower.
The below code gives a short introduction on how to extract data from both raster and shapefiles (vector data), very common operations . I will add more tips and tricks as I come across them.
# Load libraries. # For raster data require(raster) # For vector data require(sp) # Set flux tower coordinates. lat= 45.2041 lon=-68.7402 # Define lat / lon projection. lat_lon <- CRS("+init=epsg:4326") # Define UTM projection. utm <- CRS( "+proj=utm +zone=19 +north +ellps=WGS84 +datum=WGS84 +no_defs") # Read in the coordinates and assign them a projection, # otherwise they remain just 'numbers' location <- SpatialPoints(cbind(lon,lat), lat_lon) # Convert to utm using the above projection string # using spTransform. location_utm <- spTransform(location, utm) # Load raster Digital Terrain Map (DTM) data. # If the raster data has no projection, # you will have to assign a projection. # I assume the file has a projection. dtm <- raster('DTM.tif') # Relative height of the location of the tower. dtm_data <- extract(dtm,location_utm) # Read in soil shapefile. soils <- readShapeSpatial("soils.shp") # Assign projection to the soils.shp file # if not provided. proj4string(soils) <- utm # Extract soil polygon attributes. soil_attributes <- over(location_utm,soils)