8/14/2003 DESCRIPTION: GLOBAL SOIL TYPES, 0.5-DEGREE GRID (MODIFIED ZOBLER) - 106 SOIL TYPES REFERENCE: Post, W.M., and L. Zobler. 2000. Global Soil Types, 0.5-Degree Grid (Modified Zobler). Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. COMMENTS: --------- In addition to providing the Zobler soil type data in several formats, this data set also contains a series of codes used for converting the original Zobler Soil Types at 1 degree resolution to a grid containing 0.5 x 0.5 degree cells. Please note that while this data is at a 0.5 degree resolution, the true resolution and accuracy of the map is not actually increased. Rather, the 1 degree squares are divided into 4 0.5 degree squares to better represent continental boundaries and shorelines/islands. Please note that the source data for this map are distributed by Webb et al. (1991) and (2000) and include the full range of soil type classes (106). The source data, which is included with this data set, contains 2 columns of information. The first column contains a continent code and the second column is a soil type code (please see keys zsoiltype_key.txt and cont_codes.txt). NOTE: At the request of our user community, we have included GRID ASCII and ARC/INFO export file (*e00) versions of these data. These files were created using a combination of awk and perl scripts. (8/2003) If you are interested in these data files, please read ahead to the FILES and FORMAT sections of these documents. CREATING THE .5 DEGREE GRID: ---------------------------- A code was written (one2half.c) to take the file CONTIZOB.LER and divide the cells into quarters. This code also reads in a land/water file (land.wave) that specifies the cells that are identified as land at 0.5 degrees. The code checks for consistency between the newly quartered map and the land/water map to which the quartered map is to be registered. If there is a discrepency there was an attempt to fix it (a call to fixcell.c). For example, cells identified as water by the land/water mask are forced to be water in the soils map. If cells are identified as land by the land/water mask but were considered water at 1 degree, the code looks at the surrounding 8 cells and assigns the majority soil type value for the neighborhood to the cell in question. If there are no surrounding land cells then it is kept as water in the hopes that on the next pass one or more of the surrounding cells might be converted from water to a soil type. The process is iterated 5 times for the globe. The remaining cells that should be land but couldn't be determined from surrounding cells (mostly islands that are resolved at 0.5 degree but not at 1 degree) were output to a file with coordinate information. A temporary map was outputted with a flag of -9 indicating where data was required. This process was repeated for the continent codes in CONTIZOB.LER as well (one2halfc.c and fixcellc.c). The areas coded with a -9 were used to consult the printed versions of the soil map. The program manfix.c was used by an operator to interactively input the correct soil and continent codes for the map. This process could be done manually or by preparing a file of changes (new_fix.dat) and redirecting stdin. The result (contizob.half) is in the form of the original CONTIZOB.LER file but is 4 times larger. GRID ASCII (zsoiltype.dat and contcode.dat) and ESRI EXPORT file (zsoiltype.e00 and contcode.e00) versions of this data are also available for GIS users. FILES: ------ COMPANION FILES in /comp: ------------------------_ readme.txt - this file zsoiltype_key.txt - a key including the names and abbreviations of the soil types included in this data set. cont_codes.txt - a key including the continent codes used in this data set. postzobler.jpg - graphic README_images - note reminding ftp users to download all graphics and companion files. create_half_degree_grid.tar.gz - This archive contains 9 files described below. Gzip and tar utilities were used to compress these files in UNIX. The file is available at http://daac.ornl.gov/daacdata/global_soil/ZoblerSoilDerived/comp/ The following original data file, documentation, and code files are referenced in the description for creating the .5 degree grid data. readme.txt - original readme documentation CONTIZOB.LER - original data file, 1 degree resolution, contains continent code and soil type information in 2 columns land.wave - land water mask, .5 degree resolution one2half.c - c code written to divide the 1 degree soil type cells into .5 degree cells. Please see section titled "CREATING THE .5 DEGREE GRID" for more information. one2halfc.c - c code written to divide the 1 degree continent cells into .5 degree cells. Please see section titled "CREATING THE .5 EGREE GRID" for more information. fixcell.c - called from one2half.c to reassign values (soil types) of cells flagged by the land/water mask. Please see section titled "CREATING THE .5 DEGREE GRID" for more information. fixcellc.c - called from one2half.c to reassign values (continent code) of cells flagged by the land/water mask. Please see section titled "CREATING THE .5 DEGREE GRID" for more information. manfix.c - c program written to aid user in interactively assigning soil and continent codes to pixels incorrectly identified as "water". Please see section titled "CREATING THE .5 DEGREE GRID" for more information. new_fix.dat - input file written as a companion to manfix.c DATA FILES in /data: -------------------- contizob.half - data file containing continent codes and soil types, in ASCII format. (2 columns of data) z_soiltype.dat - GRID ASCII file containing soil type codes from contizob.half. contcode.dat - GRID ASCII file containing continent codes from contizob.half. z_soiltype.e00 - ESRI export file containing soil type codes from contizob.half. contcode.e00 - ESRI export file containing continent codes from contizob.half. GIS FORMATS: ------------------------------------------------------------------------------ 1. GRID ASCII - a single ASCII array with integer values. (Coordinates listed below are in decimal degrees.) The ASCII file consists of header information containing a set of keywords, followed by cell values in row-major order. The file format is: {NODATA_VALUE xxx} row 1 row 2 . . . row n where xxx is a number, and the keyword NODATA_VALUE is optional and defaults to -9999. Row 1 of the data is at the top of the grid, row 2 is just under row 1 and so on. The end of each row of data from the grid is terminated with a carriage return in the file. First six lines of file (header): ncols 720 nrows 360 xllcorner -180 yllcorner -90 cellsize 0.5 NODATA_value -9999 To import this file into ArcInfo use the following command at an ARC prompt: ASCIIGRID {INT | FLOAT} Arguments - the ASCII file to be converted. - the user specified name of the grid to be created. {INT | FLOAT} - the data type of the output grid. INT - an integer grid will be created. FLOAT - a floating-point grid will be created. Note: This data can also be imported into ArcView (with Spatial Analyst) and ArcGis as ASCII Raster data. 2. ESRI EXPORT file (*.e00) - is a proprietary format that can be imported into ARC/INFO GRID using the following command at an ARC prompt: IMPORT