This data set combines various ancillary data (geolocation, surface roughness, and photographs) collected for the Iowa Soil Moisture Experiment 2002 (SMEX02) study region.
SMEX02 Land Surface Information: Geolocation, Surface Roughness, and Photographs, Version 1
This is the most recent version of these data.
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Geographic Coverage |
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Jackson, T., M. Cosh, W. P. Dulaney, and L. McKee. 2004. SMEX02 Land Surface Information: Geolocation, Surface Roughness, and Photographs, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/R9AA6FC58HES. [Date Accessed].Detailed Data Description
This data set combines various ancillary data (geolocation, surface roughness, and photographs) collected for the Iowa Soil Moisture Experiment 2002 (SMEX02) study region.
Geolocation data are in 14 ASCII text files, including 13 tab-delimited (row/column) data files and one text document that describes the study areas and bounding boxes.
Surface roughness data are provided in two ASCII files.
Photographs are provided as JPEG image files.
Table 1 describes the variables used in the column headings for the surface roughness data files.
Heading | Description |
---|---|
file name |
Name of the original file. Includes: site ID (for example, WC08) location in the field (A, B, C, or D) 1 for in-row pictures 2 for cross-row pictures |
np |
Number of points |
sigma |
rms height |
L |
Correlation length |
adj. sigma |
Slope-corrected (adjusted) rms height |
Exp. |
The power coefficient of the autocorrelation function |
Data are available on the HTTPS site in the https://daacdata.apps.nsidc.org/pub/DATASETS/AVDM/data/soil_moisture/SMEX02/ancillary_data/
directory. Within this directory therer are five folders: geolocation_information
, landuse_classification
, photographs
, soils_database
, and surface_roughness
.
This section explains the file naming convention used for this product with an example.
Geolocation Data Files
These files are named for the locations around the study site as shown in Table 2.
File Name | Description |
---|---|
ASOS_Stations.txt |
Automated Surface Observing System (ASOS) stations |
AWOS_Stations.txt |
Automated Weather Observing System (AWOS) stations |
Bounding_Boxes.txt |
SMEX02 study areas and bounding boxes (this is a text document) |
IA_Field_Boundaries.txt |
Iowa regional field boundaries |
IA_Sites.txt |
Iowa regional sampling sites |
ISUW_Stations.txt |
Iowa Agriculture Climate Network - Iowa State University (ISU) Crop, Soil, and Environmental Sciences |
KCCI_Stations.txt |
School Network for KCCI-TV in Des Moines, Iowa |
Vegetation_Sites.txt |
Walnut Creek vegetation sampling sites |
WC_Basin.txt |
Walnut Creek watershed boundary |
WC_Field_Boundaries_V2.txt |
Walnut Creek field boundaries |
WC_Flux_Towers.txt |
Flux tower locations |
WC_Raingages.txt |
Walnut Creek rain gages |
WC_Sites.txt |
Walnut Creek sampling sites |
WC_Streamgages.txt |
Walnut Creek stream gages |
Surface Roughness
These data files are named for the type of scanning.
Example File Names
Grid: grid_scanning.txt
Slope: slope_scanning.txt
.
Photograph
Example File Name: IA13_03_062902.jpg
is from the Iowa regional area, field 13, index 03, and was taken on 29 June 2002.IAff_nn_mmddyy.jpg
WCff_nn_mmddyy.jpg
Where:
Variable | Description |
---|---|
IA |
Indicates the the Iowa Regional study region and WC indicates the Walnut Creek watershed. |
ff |
The field number in which the photograph was taken. |
nn |
The picture index number for that field. |
mmddyy |
The date (month, day, and year). |
Geolocation: Range from approximately 1 KB to 51 KB (102 KB total)
Surface Roughness: 17.2 KB and 18.5 KB
Photographs: Range from 240 KB to 2,000 KB (53.1 MB total)
Total volume of all files is approximately 54 MB.
Southernmost Latitude: 41.7° N
Northernmost Latitude: 42.66° N
Westernmost Longitude: 93.8° W
Easternmost Longitude: 93.2° W
Data were collected from 22 June 2002 through 12 July 2002.
Parameter Description
Geolocation data are provided as latitude and longitude coordinates, in decimal degrees, and in UTM coordinates, in meters.
Surface roughness data include root-mean-square height in centimeters and correlation length in centimeters.
Photographs of the study area are also provided.
Sample Data Records
The following geolocation sample is taken from the file IA_sites.txt
.
Site_ID Latitude Longitude Easting Northing IA01 42.6599 -93.7174 441207 4723296 IA02 42.5872 -93.7058 442086 4715215 IA03 42.5066 -93.7192 440911 4706278 IA04 42.4122 -93.7280 440099 4695803 IA05 42.3417 -93.7287 439977 4687974
The following surface roughness sample is from the file grid_scanning.txt
.
<------------- surface output ------------------><---Scorelat ---> grid scanning (1 cm) file name np sigma L adj.sigma Exp. Exp wc01a1 101 0.778 4.079 0.772 1 wc01a2 101 2.142 14.838 2.137 1.75 wc01b1 101 0.557 3.734 0.557 1 wc01b2 101 1.855 9.744 1.850 1.5 1.3 wc01c1 101 0.467 5.107 0.467 1
Software and Tools
Data Acquisition and Processing
Geolocation
Geolocation data are provided in both latitude and longitude (decimal degrees) and in UTM coordinates (Zone 15, in meters). Georeferencing is based on the WGS84 ellipsoid. Geolocation data were collected by a variety of methods. Some site locations were determined using Landsat Thematic Mapper (TM) imagery, some by global positioning system (GPS) measurements, some from a combination of aircraft and GPS data, and some by other methods. Table 5 shows the geolocation data sources for the various types of SMEX02 locations.
Type
|
Subtype
|
Georegistration Source
|
Data Type
|
Data Points
|
---|---|---|---|---|
ASOS Stations | Points | Unknown | Point | 15 |
AWOS Stations | Points | Unknown | Point | 33 |
Bounding Box | Boundary | TM Image | Corners | 4 |
Ground Soil Moisture | IA Sites | GPS | Point | 47 |
WC Sites | GPS | Clusters | 14*31 | |
IA Field Boundaries | TM Image | Lower Left and Upper Right Corners | 47*2 | |
WC Field Boundaries | TM Image | Lower Left and Upper Right Corners | 31*2 | |
Flux Towers | Point | GPS | Point | 14 |
ISUW Sites | Point | Unknown | Point | 12 |
KCCI Sites | Point | Unknown | Point | 40 |
Rain Gages | Point | GPS | Point | 22 |
Stream Gages | Point | GPS | Point | 5 |
Watershed | Boundary | TM Image | Boundary | 1465 |
Vegetation | Points | GPS | Point | 31*3*5 |
Surface Roughness
The surface roughness data were derived from digital photographs, then processed to produce root-mean-square (rms) height, correlation length, and correlation function. Figure 1 shows the measuring board and how it was used in the field to photograph surface roughness. The commercial program SigmaScan pro 4 was used to digitize the roughness photographs.

Before scanning, the dimensions of the board were identified using reference points on the board. The surface was scanned in two ways:
- Taking a height measurement at every cm (grid scanning)
- Taking a height measurement at every point where the slope of the surface was changing or at least every cm (slope scanning)
The grid scanning method provides a random (or normal) distribution of the surface height, which is required for a correct computation of the rms height. With this method, some variation in the surface height is neglected, which could influence the computation of the correlation length.
The slope method approximates the surface roughness more accurately by taking a height measurement at each point the slope changed, or at a minimum of every centimeter. By increasing the density of the height measurements at points with many slope changes, the sampling of height measurements may be biased. This could influence the correct computation of the rms height. Therefore, two surface height data set were created:
- Grid scanning data
- Slope scanning data
Roughness parameters were calculated using programs named surface and scorelat. The surface program calculates the rms height and the correlation length and writes the computed autocorrelation curve to a file. This program also corrects for the slope of the roughness board using a least-square fit and calculates an adjusted rms height. The investigators recommended using the adjusted rms height ("adj.sigma" in the data files). The scorelat program was used only to create an autocorrelation curve, but it uses a different algorithm than does the surface program. Both autocorrelation curves of surface and scorelat were used to determine the autocorrelation function. The scorelat program was successfully applied to only some of the digitized surfaces of the grid scanning and the slope scanning data set.
Photographs
Teams were assigned cameras throughout the experiment. Not all fields were photographed.
References and Related Publications
Contacts and Acknowledgments
Tom Jackson
US Department of Agriculture (USDA) Hydrology and Remote Sensing Lab
Beltsville, MD
USA
Mike Cosh
US Department of Agriculture (USDA) Hydrology and Remote Sensing Lab
Beltsville, MD
USA
The investigators thank the Soil Moisture Experiment 2002 Science Team, the National Soil Tilth Laboratory, the National Aeronautics and Space Administration (NASA), NASA Aqua AMSR Terrestrial Hydrology and Global Water Cycle Programs, and all those who collected and analyzed the data, including: Rogier Van der Velde, Ann Hsu, and Laura Kimes. They also want to thank the many graduate students and volunteers who collected field photographs.
Document Information
DOCUMENT CREATION DATE
January 2004
DOCUMENT REVISION DATE
November 2005