Difference between revisions of "NLCD Land Cover"

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(Manning's n: +cite)
(Manning's n)
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Actual values for your location will vary widely, the following is simply a starting point.
Actual values for your location will vary widely, the following is simply a starting point.
: ''TODO: values of 999 require values from the literature''
<!-- : ''TODO: values of 999 require values from the literature'' >
0 = 0  Unclassified
0 = 0  Unclassified
11 = 0250 Open Water
11 = 0250 Open Water
12 = 999    Perennial Snow/Ice
12 = 0220 Perennial Snow/Ice
21 = 0404 Developed, Open Space
21 = 0404 Developed, Open Space
22 = 0678 Developed, Low Intensity
22 = 0678 Developed, Low Intensity

Revision as of 21:12, 19 August 2019

NLCD2016 land cover example, south shore of Long Island, NY


  • Raster grid covering the Continental US at 30 meter resolution

From the Spearfish dataset's landcover.30m history file:

National Land Cover Data Set NLCD, U.S. Geological Survey (USGS)
The NLCD was compiled from Landsat TM imagery (circa 1992) with a spatial resolution of 30 meters supplemented by various ancillary data (where available). The satellite images were analyzed and interpreted by using very large, sometimes multi-State, image mosaics (that is, up to 18 Landsat scenes). Because a relatively small number of aerial photographs were necessarily conducted from a broad spatial perspective. Furthermore, the accuracy assessments correspond to Federal Regions, which are groupings of contiguous States. Thus, the reliability of the data is greatest at the State or multi-State level. The statistical accuracy of the data is known only for the region.

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.

  • 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


Rather than import the entire 16GB raster image, just make a virtual link to it:

r.external in=NLCD_2016_Land_Cover_L48_20190424.img out=NLCD_2016_Land_Cover_L48_20190424 title="Land Cover 2016"

Then use g.region to zoom to your area of interest and r.mapcalc to extract a subset

g.region -p n= s= e= w= res=30 align=NLCD_2016_Land_Cover_L48_20190424
r.mapcalc "NLCD.extract = NLCD_2016_Land_Cover_L48_20190424"


These can be applied with the r.category module.

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
82:Cultivated Crops
90:Woody Wetlands
95:Emergent Herbaceous Wetlands


NLCD2016 land cover classification legend from mrlc.gov

These should load in automatically, but if they don't here are the official colors which you can load in with the r.colors module's rules= option:

11 70:107:159
12 209:222:248
21 222:197:197
22 217:146:130
23 235:0:0
24 171:0:0
31 179:172:159
41 104:171:95
42 28:95:44
43 181:197:143
52 204:184:121
71 223:223:194
81 220:217:57
82 171:108:40
90 184:217:235
95 108:159:184


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 virtual reclass map with 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 Manning's n number.

Actual values for your location will vary widely, the following is simply a starting point.