Soil Datasets

Lambert Azimuthal Projection Files for soil fraction data Files for soil fraction data Data set reference code -- 1997-0012 To accommodate users with a variety of GIS software, the data giving the soil fraction percents for each of the 11 standard layers are available in several different formats. The files needed by each of the types of user below are described separately. Arc/Info polygon file users Arc/Info grid file users Other users of gridded data Local users on the ESSC network NOTE: Most of these files have been compressed using the GNU `gzip` program, as indicated by the `.gz` file extension. Users who do not have access to the `gunzip` decompression program can request that files be uncompressed prior to transfer via ftp. In some cases, however, the uncompressed file may be very much larger than the compressed version, greatly increasing file transfer time. Arc/Info polygon file users The orginal STATSGO mapunits for the 48 states have been merged into a single Arc/Info polygon (vector) coverage. The percent sand, silt, and clay in the less than 2 mm soil component for each of 11 standard layers and the mean depth to bedrock data for each mapunit are given by an auxilliary INFO table, which may be RELATEd to the mapunit coverage using "MUID" as the relate item. The needed files are mu_poly.e00.gz (116 Mbyte, uncompresses to 274 Mbyte) Mapunit polygon coverage in Arc/Info EXPORT format. mu_fract.e00.gz (382 kbyte, uncompresses to 1.9 Mbyte) INFO table giving percent sand, silt, and clay for each layer, plus depth to bedrock, in Arc/Info EXPORT format. stdlayer.e00 INFO table defining the 11 standard soil layers for which the sand/sit/clay percents were computed. Arc/Info grid file users The mapunits have been gridded at 1-km cell size. The value attribute table (VAT) for the Arc/Info grid listed below contains the mapunit indentifier, MUID, the mapunit serial number, MUSERIAL, the mean depth to bedrock, and the percents sand, silt, and clay for each standard layer. Warning -- The uncompressed version of the grid file below is very much larger than the compressed version. fractgrid.e00.gz (8.2 Mbyte, uncompresses to 123 Mbyte) 1-km grid of mapunits, including VAT, in Arc/Info format. stdlayer.e00 INFO table defining the 11 standard soil layers for which the dominant soil fraction classes were computed. Other users of gridded data The 1-km gridded data are also available as a set of three, three-dimensional arrays of 8-bit binary values, in band-sequential (BSQ) form. There are separate arrays for percent sand, silt, and clay. Each array is arranged as a set of 11 two-dimensional subarrays, givng data for each of the 11 standard layers. Within each layer, the values are arranged by horizontal rows. All values for the first layer are given first, starting with the value for the left (western) end of the top (northern-most) row, and continuing left to right along the row. The data for the last row of the first layer are then followed by the top row of the second layer, and so on. Each array contains 11 layers each containing 2889 rows of 4587 values. Code for reading the binary array is available in Fortran 77 and C. Warning -- The uncompressed version of the BSQ files below is very much larger than the compressed version. clay.bsq.gz (14 Mbyte, uncompresses to 146 Mbyte) Three dimensional array of percent clay for each grid cell and soil layer. sand.bsq.gz (15 Mbyte, uncompresses to 146 Mbyte) Three dimensional array of percent sand for each grid cell and soil layer. silt.bsq.gz (15 Mbyte, uncompresses to 146 Mbyte) Three dimensional array of percent silt for each grid cell and soil layer. mu_fract.ascii.gz (292 kbyte, uncompresses to 2. Mbyte) Table giving, for each STATSGO mapunit, the mapunit ID, mapunit serial number, mean depth to bedrock in cm, and percents sand, silt, and clay for each standard layer. stdlayer.ascii Table defining the 11 standard soil layers for which the soil fractions were computed. The same BSQ arrays are also available in LAS format (files sand.img.gz, silt.img.gz, clay.img.gz and the corresponding .ddr files). Local users on the ESSC network The filesystems containing the datasets are cross-mounted on the local ESSC computer network. Local Arc/Info users may find it more convenient to copy necessary files directly to their own workspaces using the Arc/Info COPY and COPYINFO commands. The needed directories and files (under directory $DSREF/1997-0012/) are fractgrid Arc/Info grid representation of mapunits; the soil fraction information from table MU_FRACT is included in the VAT for this grid. ../mapunits/mu_poly Arc/Info coverage containing polygon version of mapunit boundaries. info!MU_FRACT INFO table giving percent sand, silt, and clay in the lesss than 2 mm soil fraction for each standard layer of each mapunit, plus depth to bedrock. info!STDLAYER Table defining the 11 standard soil layers for which the dominant soil fraction classes were computed. Last change: 2006 Apr 14, R. A. 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Comments and Questions 3/8/2006