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Data Set ID:
NSIDC-0278

SMEX02 Land Surface Information: Soils Database, Version 1

This data set includes soil moisture data for the following 10 Iowa counties: Boone, Dallas, Franklin, Hamilton, Hardin, Jasper, Marshall, Polk, Story, and Wright. These data were created by appending existing county digital soils data provided by the Iowa Cooperative Soil Survey (ICCS) and clipping them by the SMEX02 project area boundary.

Geographic Coverage

Parameter(s):
  • Boundaries > Boundary Surveys
  • Land Use/Land Cover > Land Use Classes
  • Soils > Soil Classification
Spatial Coverage:
  • N: 42.73229, S: 41.69459, E: -93.16104, W: -93.84162

Spatial Resolution: Not Specified
Temporal Coverage:
  • 25 June 2002 to 12 July 2002
Temporal Resolution: Not specified
Data Format(s):
  • ESRI Shapefile
Platform(s) AERIAL PHOTOGRAPHS
Sensor(s): CAMERAS
Version: V1
Data Contributor(s): Douglas Miller
Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Miller, D. 2006. SMEX02 Land Surface Information: Soils Database, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/RS5JQW0QA5XG. [Date Accessed].

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Detailed Data Description

Format

These data files are ESRI shapefiles. A general description of each file type follows:

A detailed description of the "soils.dbf", "soils_wc_all.dbf", and "iaregnsoil.dbf" file variables is described in the Soils Database: Fields Table.

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File and Directory Structure

The "soils_database" directory contains two subdirectories, "Iowa" and "Walnut Creek". The "Iowa" subdirectory contains regional data, whereas the "Walnut Creek" subdirectory contains only the data for the Walnut Creek watershed.

.shp cartographic vector data with a database table lookup association using .dbf and .shx files
.shx file holding data for the actual vertices
.dbf file holding index data pointing to specific structures in the .shp file
.prj a text description of the coordinate system; external projection file
.sbn file holding additional shapefile components and spatial indices
.sbx file holding additional shapefile components and spatial indices
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File Naming Convention

"Iowa Regional Data" subdirectory (260 MB):

regnDrain.* This line coverage contains data about drainage features from the ICSS.
regnSect.* This polygon coverage contains geographical boundaries from the Public Land Survey System (PLSS) of the Iowa Department of Natural Resources GIS Library.
regnTwps.* This polygon coverage contains PLSS township boundaries from the of the US Geological Survey (USGS) National Atlas.
regnRR.* This line coverage contains geographic information about railroads from the Census 2000 Topologically Integrated Geographic Encoding and Referencing (TIGER) database.
regnPts.* These files contain SMEX02 regional sample points.
regnRoads.* This line coverage contains geographic information about road centerlines from the Census 2000 TIGER database.
iaregnsoil_read_me.htm This file contains the SMEX02 Regional Soils data set notes.
iaregnsoil.* This polygon coverage contains digital soil map units from the ICSS.
regnStreams.* This line coverage contains geographic information about stream centerlines from the Census 2000 TIGER database.
Iowa_soils_metadata.pdf This file contains the ICSS digital soil map data documentation.

"Walnut Creek Data" subdirectory (39.7 MB):

drainage.* This line coverage contains data about drainage features from the ICSS.
fields.* This polygon coverage contains SMEX02 field boundaries.
plss_sect.* This polygon coverage contains geographical boundaries from the PLSS of the Iowa Department of Natural Resources NRGIS Library.
plss_twp.* This polygon coverage contains PLSS township boundaries from the of the USGS National Atlas.
railroad.* This line coverage contains geographic information about railroads from the Census 2000 TIGER database.
roads.* This line coverage contains geographic information about road centerlines from the Census 2000 TIGER database.
soils_wc_all.* This polygon coverage contains digital soil map units from the ICSS.
soils.* This polygon coverage contains digital soil map units from the ICSS clipped by research field boundaries.
streams.* This line coverage contains geographic information about stream centerlines from the Census 2000 TIGER database.
townLimits.* This polygon coverage contains the town limits from the Census 2000 TIGER database.

Both directories contain the "ispaid_user_guide.pdf" file, which is the Iowa Soil Properties and Interpretation Database (ISPAID) guide and includes a description of the attributes contained in digital soils data shapefiles.

The "*" symbol represents the various file extensions described in the Format section.

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File Size

File sizes range from 1 KB to about 174 MB.

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Volume

The entire data set, including both of the subdirectories, is 293 MB

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Spatial Coverage

The following 10 counties comprise the data set:  Boone, Dallas, Franklin, Hamilton, Hardin, Jasper, Marshall, Polk, Story, and Wright.

Southernmost Latitude: 41.69459° N
Northernmost Latitude: 42.73229° N
Westernmost Longitude: 93.84162° W
Easternmost Longitude: 93.16104° W

Spatial Resolution

The minimum size delineation of soil polygons is two acres.

Projection Description

Data are based on the North American Datum of 1983 (NAD83). The data were collected from Universal Transverse Mercator (UTM) Zone 15.

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Temporal Coverage

Because this data set was created by appending existing county digital soils data provided by ICCS and clipping them by the SMEX02 project area boundary, the dates of data acquisition are highly variable; therefore, they are unspecified.

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Parameter or Variable

Parameter Description

The data contain geographic information such as railroad, road, and stream locations; drainage features; political boundaries; and soil classifications. Please refer to the File Naming Convention section.

Parameter Source

Data were derived from aerial photography and topographic maps of the study area.

Sample Data Image

As displayed in ENVI, the image below was created with data from the Walnut Creek subdirectory including streams, drainage, soils, and field coverage.

ENVI image created with Walnut Creek data

Sample Data Record

The sample data below is from the "soils.dbf" file. Because the file includes 85 columns, only the first 9 columns and last column of data are shown below.

OBJECTID
SITE_ID
Measure_Ty
SMS
SMU
SCSSOIL5
SOILNAME
LCC
PRIMELND
...
Shape_Area
1
28
SM
138B
0138B1
IA0074
CLARION
2E
P
...
8745.915014
2
28
SM
138B
0138B1
IA0074
CLARION
2E
P
...
9098.510097

The column headings correspond to the following (as is described in "ispaid_user_guide.pdf"):

OBJECTID Object identification number
SITE_ID Site Identification number
Measure_Ty This field is not applicable and should be disregarded.
SMS The Soil Map Symbol is the symbol as used on the soil map sheets.
SMU The Soil Map Unit symbol identifies the soil type, the slope class, and the erosion phase.
SCSSOIL5 The Soils-5 Number is a record number from a National Resources Conservation Services form, NRCS-SOI-5. The first two letters indicate the state.
SOILNAME The Soil Name can be the soil series name or may include specific soil phase modifiers, such as texture of the surface horizon, profile depth limits, flooding frequency, overwash characteristics, etc.
LCC In general, the Land Capability Classification shows the suitability of soils for most kinds of field crops.
PRIMELND The United States Department of Agriculture (USDA) Prime Farmland rating defines land that is best suited to food, feed, forage, fiber, and oilseed crops.
Shape_Area This field is not applicable and should be disregarded.
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Software and Tools

The data can be viewed using ArcView/GIS software.

Quality Assessment

With the exception of Polk county, the source of all soil property attributes is the Iowa Soil Properties and Interpretations Database (ISPAID).  Soil Survey Geographic Database (SSURGO, version 2) and Map Unit Interpretation Record (MUIR) databases were used to populate a selected set of soil property attributes for Polk county.  Due to dissimilarity between these data sets, attribute values for Polk county may differ from those of similar soils observed in neighboring counties.

Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of soils of other taxonomic classes. Consequently, every map unit is made up of the soil or soils for which it is named and some soils that belong to other taxonomic classes. Please see "iowa_soils_metadata.pdf" for more details.

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Data Acquisition and Processing

Data Acquisition Methods

This data set was created by appending existing county digital soils data provided by the ICSS and clipping these data by the SMEX02 project area boundary.

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Derivation Techniques and Algorithms

Processing Steps

At a ground resolution of two meters, 1:15,840 and 1:20,000 scale mylar map sheets were scanned with an Optronics camera at 200 dots per inch (DPI). The map sheets were originally drawn on black and white, rectified aerial photographs. These aerial photographs were not ortho-rectified; thus, soil lines contain terrain distortions inherited from the imagery. The maps were edited with Map Editing Software (MES) at the University of Minnesota. The map sheets were clipped to individual sections having a raster resolution of 320 x 200 pixels (a typical ground resolution of 5 x 8 meters). The raster images were converted to vector format, and then converted to Arc/Info format. 

Soil data was transformed to fit the UTM coordinate system using the map registration marks from Iowa Department of Natural Resources (DNR), Natural Resources Geographic Information Systems (NRGIS) county PLSS files. PLSS coverages were digitized from 24,000 USGS topographic maps and have 22-meter root-mean-square (RMS) accuracy.

Section files were appended to the township level by the Iowa Geological Survey Bureau and the Iowa State University GIS Facility. Township level data that was appended to county-wide level data and projected to UTM Zone 15 North American Datum of 1983 (NAD83) Geodetic Reference System 1980 (GRS80) was converted to ESRI shapefile format by USDA Natural Resources Conservation Service in Ames, Iowa.

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Contacts and Acknowledgments

Douglas Miller 
Pennsylvania State University 
2217 Earth-Engineering Sciences Bldg. 
University Park, PA 16802 USA 

Document Information

DOCUMENT CREATION DATE

February 2006

No technical references available for this data set.
No FAQs or How Tos available for this data set.

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