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

We kindly request that you cite the use of this data set in a publication using the following citation example. For more information, see our Use and Copyright Web page.

Jackson, T., M. Cosh, W. P. Dulaney, and L. McKee. 2004. SMEX02 Land Surface Information: Geolocation, Surface Roughness, and Photographs. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.

Overview Table

Category Description
Data format Geolocation data: ASCII text files
Surface roughness: ASCII text files
Photographs: JPEG image files
Spatial coverage and resolution Southernmost Latitude: 41.7° N
Northernmost Latitude: 42.66° N
Westernmost Longitude: 93.8° W
Easternmost Longitude: 93.2° W
Temporal coverage and resolution Data were collected from 22 June 2002 through 12 July 2002.
Tools for accessing data None
File naming convention Geolocation: Named for the locations around the study site
Surface Roughness: Two files named for the type of scanning, either grid ("grid_scanning.txt") or slope ("slope_scanning.txt")
Photographs: Files are named "IAff_nn_mmddyy.jpg" or "WCff_nn_mmddyy.jpg"
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)
Parameter(s) Geolocation coordinates, surface roughness measurements, and photographs
Procedures for obtaining data Data are available via FTP.

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

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

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.

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

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:

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 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:

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

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.

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. 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.

Surface roughness measuring board photograph

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.

AMSR-E Advanced Microwave Scanning Radiometer - Earth Observing System
ASCII American Standard Code for Information Interchange
FTP File Transfer Protocol
GPS Global Positioning System
JPEG Joint Photographic Experts Group
NASA National Aeronautics and Space Administration
NSIDC National Snow and Ice Data Center
RMS Root Mean Square
SMEX Soil Moisture Experiment
TM Thematic Mapper
URL Uniform Resource Locator
UTM Universal Transverse Mercator

Document Creation Date

January 2004

Document Revision Date

November 2005

Document URL

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