SMEX02 Land Surface Information: Geolocation, Surface Roughness, and Photographs

Summary

This data set combines various ancillary data (geolocation, surface roughness, and photographs) collected for the Iowa Soil Moisture Experiment 2002 (SMEX02) study region. The geolocation files provide geographic coordinates for the SMEX02 test sites, study areas, and instrumentation. The surface roughness data are derived from photographs taken at representative watershed sampling locations. The photographs were taken in the field at various locations during the experiments.

Data are provided in ASCII text files and JPEG image files, and are available via FTP.

These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.

Citing These Data

Please note that the citation depends on the type of data you are using, as follows:

Geolocation: Jackson, T. J., M. H. Cosh, and W. Dulaney. 2004. SMEX02 land surface information: geolocation, surface roughness, and photographs. Boulder, CO: National Snow and Ice Data Center. Digital media.
Surface roughness: Jackson, T. J. and L. McKee. 2004. SMEX02 land surface information: geolocation, surface roughness, and photographs. Boulder, CO: National Snow and Ice Data Center. Digital media.
Photographs: Jackson, T. J. and M. H. Cosh. 2004. SMEX02 land surface information: geolocation, surface roughness, and photographs. Boulder, CO: National Snow and Ice Data Center. Digital media.

Overview Table

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigator(s) Name and Title

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

Technical Contact

Acknowledgements

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.

2. Detailed Data Description

Format

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. The following table describes the columns in the surface roughness data files.

Photographs are provided as JPEG image files.

File and Directory Structure

Geolocation, surface roughness, and photographs directories are located under the SMEX02 ancillary data directory on the FTP site, as shown in this image:

File Naming Convention

Geolocation data files are named for the locations around the study site, as shown in the following table:

Surface roughness data files are named for the type of scanning; either grid ("grid_scanning.txt") or slope ("slope_scanning.txt").

Photograph files are named "IAff_nn_mmddyy.jpg" or "WCff_nn_mmddyy.jpg" where:

• IA indicates the the Iowa Regional study region and WC indicates the Walnut Creek watershed.
• ff is the field number in which the photograph was taken.
• nn is the picture index number for that field.
• mmddyy is the date (month, day, and year).

For example, the file "IA13_03_062902.jpg" is from the Iowa regional area, field 13, index 03, and was taken on 29 June 2002.

File Size

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)

Spatial Coverage

Southernmost Latitude: 41.7° N
Northernmost Latitude: 42.66° N
Westernmost Longitude: 93.8° W
Easternmost Longitude: 93.2° W

Temporal Coverage

Data were collected from 22 June 2002 through 12 July 2002.

Parameter or Variable

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    

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

Total volume of all files is approximately 54 MB.

Related Data Collections

• AMSR-E Validation Data
• AMSR-E Data at NSIDC
• NASA Land Surface Hydrology/Soil Moisture Field Experiments Archive

4. 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. The following table shows the geolocation data sources for the various types of SMEX02 locations.

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. The image below 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:

1. Taking a height measurement at every cm (grid scanning)
2. 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:

1. Grid scanning data
2. 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.

5. References and Related Publications

Please see the SMEX02 Web site for more information.

Dobson, M. C. and Ulaby, F. T. 1998. Mapping soil moisture distribution with imaging radar. In Principles & application of imaging radar, Henderson, F. M. and Lewis, A. J., 407- 430, New York: John Wiley & Sons.

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

Document Creation Date

January 2004

Document Revision Date

November 2005

Document URL

http://nsidc.org/data/docs/daac/nsidc0204_smex_ancillary.gd.html