NLCD Land Cover
About
- Raster grid covering the Continental US at 30 meter resoltion
Obtaining data from the USGS
The classic Spearfish GRASS sample dataset contains a landcover.30m raster map which is an excerpt from an older version of the NLCD dataset.
- Download site: https://www.mrlc.gov/data
- Data is provided in ERDAS Imagine .img format.
- As of April 2019 the zipped dataset is a 1.4 GB.
- Create an Albers location
- this can also be done automatically with the Location Wizard using the downloaded .img file.
Here are the values for the CONUS dataset:
name: Albers Equal Area proj: aea datum: wgs84 ellps: wgs84 lat_1: 29.5 lat_2: 45.5 lat_0: 23 lon_0: -96 x_0: 0 y_0: 0 towgs84: 0,0,0,0,0,0,0 no_defs: defined
- It is very large, connect to it with r.external then crop out the section you need with g.region and r.mapcalc.
Categories
These can be applied with the r.category module.
0:Unclassified 11:Open Water 12:Perennial Snow/Ice 21:Developed, Open Space 22:Developed, Low Intensity 23:Developed, Medium Intensity 24:Developed, High Intensity 31:Barren Land 41:Deciduous Forest 42:Evergreen Forest 43:Mixed Forest 52:Shrub/Scrub 71:Herbaceous 81:Hay/Pasture 82:Cultivated Crops 90:Woody Wetlands 95:Emergent Herbaceous Wetlands
Colors
These should load in automatically, but if they don't here are the official colors:
Legend
Use the -n and -c flags of d.legend to limit the legend to named categories.
Manning's n
For using as a basis for Manning's n friction coefficients, you can make a reclass map with the r.reclass. The module will only reclass as integers so the table below is reclassed into parts per thousand. Crop your area of interest with r.mapcalc and divide by 1000.0 at the same time to get the Mannings n number.
- TODO: values of 999 require values from the literature
0 = 0 Unclassified 11 = 999 Open Water 12 = 999 Perennial Snow/Ice 21 = 0404 Developed, Open Space 22 = 0678 Developed, Low Intensity 23 = 0678 Developed, Medium Intensity 24 = 0404 Developed, High Intensity 31 = 0113 Barren Land 41 = 3600 Deciduous Forest 42 = 3200 Evergreen Forest 43 = 4000 Mixed Forest 52 = 4000 Shrub/Scrub 71 = 3680 Herbaceous 81 = 3250 Hay/Pasture 82 = 999 Cultivated Crops 90 = 0860 Woody Wetlands 95 = 1825 Emergent Herbaceous Wetlands