SAFARI 2000 Potential Vegetation, 5-Min (Ramankutty and Foley) --------------------------------------------------- Abstract -------- The data set consists of a southern Africa subset of the 5min resolution Global Potential Vegetation data set developed by Navin Ramankutty and Jon Foley at the University of Wisconsin. The original map was derived at a 5min resolution and contains natural vegetation classified into 15 types. This data set is derived mainly from the DISCover land cover data set, with the regions dominated by land use filled using the vegetation data set of Haxeltine and Prentice (1996). The data set represents the world's "potential" vegetation (i.e., vegetation that would most likely exist now in the absence of human activities), and not necessarily "natural" pre-settlement vegetation. This is because human activities such as fire suppression have modified the stages of succession at which vegetation communities exist. ========================================================================= Background Information ---------------------- Investigators: Navin Ramankutty nramanku@students.wisc.edu Jonathan Foley jfoley@facstaff.wisc.ed Project: SAFARI 2000 Data Set Title: SAFARI 2000 Potential Vegetation, 5-Min (Ramankutty and Foley) Site: Southern Africa Westernmost Longitude: 5 Easternmost Longitude: 60 Northernmost Latitude: 5 Southernmost Latitude: -35 Data Set Citation: Ramankutty, Navin, and Jonathan A. Foley. 2002. SAFARI 2000 Potential Vegetation, 5-min (Ramankutty and Foley). Available on-line [http://www.daac.ornl.gov/] from the Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. Southern African subset extractions of this data were performed by Oak Ridge National Laboratory: ORNL DAAC User Services Office ornldaac@ornl.gov +1 (423) 241-3952 ========================================================================= ASCII File Information ---------------------- The data file is in ASCII Grid format for ArcInfo. The file contains a single ASCII array with integer values. Data values range from 1 to 14 and the nodata value is -9999. Coordinates listed below are in decimal degrees. Rows 480 Columns 660 UpLeftX 5 UpLeftY 5 LoRightX 60 LoRightY -35 cellsize 0.083333336 Projection geographic The ASCII file consists of header information containing a set of keywords, followed by cell values in row-major order. The file format is: {NCOLS xxx} {NROWS xxx} {XLLCORNER xxx} {YLLCORNER xxx} {CELLSIZE xxx} {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. To import this file into ArcInfo use the following command at an ARC prompt: ASCIIGRID {in_ascii_file} {out_grid} {INT | FLOAT} Arguments: {in_ascii_file} - the ASCII file to be converted. {out_grid} - the 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. Binary File Information ----------------------- The ASCII data file has also been converted into a binary image file that can be viewed in any standard image viewing package. The file is a single-byte image, no header, 660 columns by 480 rows. Missing data (ASCII -9999) have been converted to the maximum value of 255. File Compression Information ---------------------------- For this archive, the data files have been compressed with the MS Windows-standard Zip compression scheme. These files were compressed using Aladdin's DropZip on a Macintosh. DropZip uses the Lempel-Ziv algorithm, also used in Zip and PKZIP programs. The compressed files may be uncompressed using PKZIP (with the -expand option) on MS Windows and UNIX, or with StuffIt Expander on the Mac OS. You can get newer versions from the PKZIP Web site at http://www.pkware.com/shareware/. ========================================================================= Procedure Used to Create the Southern Africa Subset --------------------------------------------------- The original data were obtained and read following the directions in the original documentation. The data were converted to ASCII arrays and then imported into ArcInfo using the ASCIIGRID command. Using GRID (a raster- or cell-based geoprocessing toolbox that is integrated with ArcInfo) the SETWINDOW command was used to define the subarea of interest. This subarea was defined by identifying the bounding coordinates as follows: x_min 5 y_min -35 x_max 60 y_max 5 The "snap_grid" option of the SETWINDOW command was used. This snaps the lower-left corner of the specified window to the lower-left corner of the nearest cell in the snap_grid and snaps the upper-right corner of the specified window to the upper-right corner of the nearest cell in the snap_grid. In this case the snap_grid is an original data grid. The purpose of this is to ensure the proper registration of the newly set analysis window. The command format used is as follows: SETWINDOW x_min y_min x_max y_max original_grid Once the window was set, creating the new grid was simply a matter of setting the new subset grid equal to the original grid. subset_grid = original_grid An ASCII array was created from the new subset grid using the GRID command GRIDASCII. file.dat = GRIDASCII(subset_grid) ========================================================================= Legend & Additional Sources of Information ------------------------------------------ The following legend is used for the 15 vegetation types contained in the original data set: 1 Tropical Evergreen Forest/Woodland 2 Tropical Deciduous Forest/Woodland 3 Temperate Broadleaf Evergreen Forest/Woodland 4 Temperate Needleleaf Evergreen Forest/Woodland 5 Temperate Deciduous Forest/Woodland 6 Boreal Evergreen Forest/Woodland 7 Boreal Deciduous Forest/Woodland 8 Evergreen/Deciduous Mixed Forest/Woodland 9 Savanna 10 Grassland/Steppe 11 Dense Shrubland 12 Open Shrubland 13 Tundra 14 Desert 15 Polar Desert/Rock/Ice Although not all of these categories may be represented in the subset of the data, the original legend has been retained. Complete information on the Potential Vegetation data set generated by Navin Ramankutty and Jonathan Foley at the University of Wisconsin can be found in the following publication: Ramankutty, N., and J.A. Foley (1999). Estimating historical changes in global land cover: croplands from 1700 to 1992, Global Biogeochemical Cycles 13: (4) 997-1027 DEC 1999.