Soils Map (5.9 kb)
Background Extent of Coverage Acquisition Sources Processing Steps Data Characteristics Spatial Resolution Temporal Coverage Data Organization Data Availability Procedures for Obtaining Data Products and Services Applications and Related Data Sets References Appendix
The World Soil data set was compiled from the FAO Soil Map of the World by L. Zobler (1986). The major components of the data set are soil classification, soil texture, soil slope and a file reconciling the differences between Matthew's Global Vegetation Data Set and FAO sources. The resolution of the data is one degree latitude by one degree longitude. Details of the data files are:
The World_Soil data set is global in extent.
In the compilation of the original FAO Soil Map of the World, about 11,000 maps were reviewed. These maps varied widely in reliability, detail, scales, and methodologies. Source maps were ranked for reliability as 1 - systematic surveys, 2 - reconnaissance surveys, and 3 - general information surveys. These rankings were not considered during compilation of the soil data set, but were recorded to give a summary of source reliability for each continent.
This data set is compiled by generalizing the FAO Soil Map of the World. Data completeness is cross-referenced to the Matthews' Global Vegetation Data Set. For example, where the Zobler data set was coded as water, and the Matthews data set was coded as land, an adjacent value was included from the the soil map.
The Zobler soil classification scheme differs from most other soil data sets in that more complete information on texture, slope, and phase is included for each map unit. Compared with the Wilson and Henderson-Sellers soil data set, the Zobler compilation provides more detailed information for each one by one degree cell. The Wilson scheme has 21 soil types based on combinations of three colors, three textures, and three drainage classes. Zobler separates soil type from both texture and slope, having ten texture and nine slope classes. The Zobler compilation is also easily converted for compatibility with either Matthews' global vegetation data set or the FAO Soil Map of the World.
Separation of soil classification, texture, slope, and phase are useful as independent data sets. Comparisons between each parameter and with the Matthews global vegetation data are also useful for studies in forestry, agriculture, hydrology, and other research areas. A dot grid overlay was used to determine the predominate map unit present in each one-degree cell.
The Zobler classification scheme addresses several important soil characteristics that influence climate parameters, such as soil texture, structure, depth, permeability, mineralogical data and color. Explicit rules for gathering data were followed. Land cells are defined as a one degree by one degree cell covered by more than 50 percent land. Land glaciers are included as land cells, but inland water bodies are labeled water cells only if the area of water is greater than 50 percent.
Each cell is identified by the latitude/longitude coordinates of its northwest corner. Latitudes increase positively north of the equator, negatively south. Longitudes are positive east of the prime meridian and negative to the west.
The soil classification units are arranged in a scheme based on inherent soil profile properties. The FAO system has two levels: the upper level with 26 soil classes, and the lower with 106. The following table lists the 26 primary soil classes:
Soil Classification Code Soil Classification Code =================== ==== =================== ==== Fluvisols J Arenosols Q Solonchaks Z Kastanozems K Gleysols G Rendzinas E Solonetz S Chernozems C Rankers U Regosols R Andosols T Yermosols Y Phaeozems H Lithosols I Vertisols V Xerosols X Greyzems M Cambisols B Podzoluvisols D Acrisols A Histosols O Podzols P Nitosols N Luvisols L Planosols W Ferralsols F
Soil texture codes are obtained from the upper 30 cm of the dominant soil unit in the cell. The codes represent the relative proportions of clay (less than 2 micrometers in size), silt (2-50 micrometers), and sand (50-200 micrometers). Three basic classes are named coarse, medium and fine. Varying combinations of these three classes give a total of seven texture classes. Slope is patterned similarly, with three basic classes of: level to gently undulating (0% - 8%), rolling to hilly (8% - 30%), and steeply dissected to mountainous (> 30%). A list of the ten texture and nine slope classes, as well as their associated codes, can be found in the Texture and Slope Table.
Soil phases are properties of soil units that influence its use and management, but are not diagnostic for the separation of the soil units. This information is provided by the FAO map as overprints apart from the soil map unit association. A list of each soil phase along with the associated codes can be found in the Soil Phases Table.
A special code (SP) is used to identify land cells that have missing data in some of the fields and to identify cells that have conflicting nominal classification (land, land-ice, water) between Matthews and Zobler. These codes allow the user to reproduce the actual FAO map unit chosen to characterize a cell by checking for these codes in the SP field and masking the appropriate fields.
Spatial Resolution
The resolution of the data set is one degree latitude by one degree longitude.
The source for these compilations is the FAO Soil Map of the World published in ten volumes between 1971 and 1979. Matthews' global vegetation data set (1984) was used for the insertion of land type, land-ice and water information.
Both the National Center for Atmospheric Research (NCAR) and NASA Climate Data System (NCDS) standard format for this data set is one 9-track, 1600 bpi labeled EBCDIC CCT. Each tape has four files ordered in a standard 360 by 180 data matrix. The first three files are subsets of the fourth file. The tape contains soil classification as the first file, soil texture as the second, surface slope as the third, and the complete FAO Soil Map of the World as the fourth. NCDS has also reformatted the data set into the NCDS Common Data Format (CDF). This format is stored in a special data set independent format which is self-describing in that it allows the user to use all manipulation and display functions created by NCDS by simply specifying the CDF name as input.
Zobler data are available from the National Center for Atmospheric Research and the NASA Climate Data System data center.
To place orders and to obtain additional information regarding technical details, ancillary products, and pricing schedules, contact:
National Center for Atmospheric ResearchNASA Climate Data SystemThe GLIS INVENTORY and ORDER screens may also be used for further information on ordering Zobler World Soils data.
The standard format from all of the distributing centers for this data is one 9-track, 1600 bpi labeled EBCDIC CCT. NCDS has also reformatted the data set into the NCDS Common Data Format (CDF). This format is stored in a special data set independent format which is self-describing in that it allows the user to use all manipulation and display functions created by NCDS by simply specifying the CDF name as input.
Applications and Related Data Sets
Elaine Matthews of the Goddard Institute for Space Studies has produced a global data set of vegetation type, cultivation intensity, and seasonal albedo. It is compiled from about 100 published map sources with reference to a large collection of satellite imagery. The resolution is 1 degree by 1 degree, making it suitable for direct comparison with the Zobler soils data. More information is available from the Matthews Global Vegetation (GVDS) Guide.
Texture Class Code Slope Class (%) Code ============= ==== =============== ==== Coarse 1 0 - 8 1 Medium 2 8 - 30 2 Fine 3 > 30 3 Coarse-Medium 4 0 - 30 4 Coarse-Fine 5 0 - 8, > 30 5 Medium-Fine 6 8 - 30, > 30 6 Coarse-Medium-Fine 7 0 - 8, 8 - 30, > 30 7 Organic 8 Land-Ice 9 Land-Ice 9 Water ` ' Water ` '
Soil Phase Code Soil Phase Code ========== ==== ========== ==== Stony 01 Cerrado 12 Lithic 02 Sodic 13 Petric 03 Permafrost 21 Petroferic 04 Intermittant Permafrost 22 Petrocalcic 05 Glacial 23 Petrogypsic 06 Ponded 24 Fragipan 07 Dunes, Sands 25 Duripan 08 Rock Debris 26 Saline 09 Salt Flats 27 Phreatic 11SOILWRLD Data Fields
Mnemonic Data Type Field description
======== ========= =================
LAT I5 Latitude of northwest corner of cell
LON I5 Longitude of northwest corner of cell
SU A2 Two-letter SOIL UNIT code
SUBSID A6 Associated and included SUBSIDIARY
soil units
TEX A3 TEXTURE codes
SLP A3 SLOPE codes
PHS A15 A string of one- and two-digit PHASE
symbols, if any
SP(3) A2 A three-element array of two-digit
SPECIAL codes used to mask record
attributes
AREA A3 A three-letter code that nominally
identifies a broad regional
location of the cell
Notes:
Texture Code Texture Class ============ ============= '1 ' coarse '2 ' medium '3 ' fine '12 ' coarse-medium '13 ' coarse-fine '23 ' medium-fine '123' coarse-medium-fine '9 ' organic ' ' land-ice
Slope Code Percent Slope Class ========== =================== 'A ' 0 - 8 'B ' 8 - 30 'C ' > 30 'AB ' 0 - 30 'AC ' 0 - 8, > 30 'BC ' 8 - 30, > 30 'ABC' 0 - 8, 8 - 30, > 30 ' ' land-ice
Phase Code Meaning Phase Code Meaning
========== ======= ========== =======
'1' stony '11' phreactic
'2' lithic '12' cerrado
'3' petric '13' sodic
'4' petroferric '21' permafrost
'5' petrocalcic '22' intermittent
permafrost
'6' petrogypsic '23' glacier
(e.g., land-ice)
'7' fragipan '24' ponded
'8' duripan '25' dunes, sands
'9' saline '26' rock debris
SP Code Meaning
======= =======
'99' No soil information present on the map;
SU, TEX and SLP fields filled
'88' Texture information missing; TEX field filled
'77' Slope information missing; SLP field filled
'44' Land cell not present on FAO map, classified
as land-ice
'33' Land cell not present on FAO map, classified
as soil; SU, TEX and SLP fields filled
'66' Cell classified as land-ice by Zobler, and as
vegetation (soil implied) by Matthews
'55' Cell classified as soil by Zobler, and as
land-ice by Matthews
Area Area Code Meaning Code Meaning ==== ======= ==== ======= 'AUS' Australia, S. Pacific 'SAM' South America 'AFR' Africa 'NCA' North Central Asia 'EUR' Europe 'SAS' Southern Asia 'NAM' North America 'SEA' South East Asia