Data Set ID:

SMAPVEX12 Probe-Based In Situ Soil Moisture Data for Agricultural Area, Version 1

This data set contains in situ soil moisture data collected at several agricultural sites as part of the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12).

This is the most recent version of these data.

STANDARD Level of Service

Data: Data integrity and usability verified

Documentation: Key metadata and user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools

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Data Format(s):
  • ASCII Text
Spatial Coverage:
N: 49.96, 
S: 49.44, 
E: -97.85, 
W: -98.51
Spatial Resolution:
  • 0.8 km x 0.8 km
Temporal Coverage:
  • 7 June 2012 to 19 July 2012
Temporal Resolution2 days to 3 daysMetadata XML:View Metadata Record
Data Contributor(s):Paul Bullock, Aaron Berg

Geographic Coverage

Other Access Options

Other Access Options


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.

Wiseman, G., A. Berg, and P. Bullock. 2014. SMAPVEX12 Probe-Based In Situ Soil Moisture Data for Agricultural Area, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: [Date Accessed].
20 February 2020
Last modified: 
20 February 2020

Data Description

This data set is comprised of in situ measurements for the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX2012). The study site was divided into regional squares, approximately 800 m by 800 m in size, with several sample point locations.


Parameters in this data set include volumetric soil moisture and real part of the dielectric constant. Table 1 describes the units of measurement and sources of each parameter.

Table 1. Parameter Units and Sensors
Parameter Unit of Measurement Sensor Valid range
Volumetric soil moisture Water Fraction Volume (m3/m3) Theta and Hydra Probes 0 - 60% 
Real part of the dielectric constant Unitless Theta and Hydra Probes 0 - 110

File Information

Format and File Contents

Data are provided in ASCII text files.
SV12PSMA_Soil_Moisture_Handheld_ver4.txt contains the soil moisture data from ground sampling.
Field_Sites_ver4_coords.txt contains the UTM coordinates for the sampling points.

Table 2 describes the soil sampling data columns of the data file, while table 3 describes the columns of the geolocation file.

Table 2. Data Fields and Descriptions

Column Heading


OBJECT_ID ID of the sample
Sample_Date 2-digit month/2-digit day/4-digit year
Sample Time 2-digit hour:2-digit minute:2-digit second
Site_ID ID of the field and the sample point within the field
Soil_Moisture_Cal Calibrated volumetric soil moisture in m3/m3
Soil_Real_Dielectric Real part of the dielectric constant measured by the probe
Source Identifies the type of the probe used (either Hydra or Theta probe)
Calibration Identifies whether general or field specific calibration was applied
Comments Any remarks regarding the sample

Missing data are represented by a blank [ ], and by -9999 for soil moisture and real part of the dielectric constant.

Table 3. Data Fields and Descriptions

Column Heading


OBJECTID ID of the data record
Site_ID ID of the field and the sample point within the field
X UTM easting coordinate (meters)
Y UTM northing coordinate (meters)

Spatial Information


Southernmost Latitude: 49.44°N
Northernmost Latitude: 49.96°N
Westernmost Longitude: 98.51°W
Easternmost Longitude: 97.85°W


Sampling was performed on sites approximately one quarter section (0.8 km by 0.8 km) in size.


Data are provided in Universal Transverse Mercator (UTM), Zone 14 N, World Geodetic System 1984 (WGS84) coordinates.

Temporal Information

Coverage and Resolution

Measurements were taken every one to five days from 07 June 2012 through 19 July 2012.

Software and Tools

No special tools are required to view these data. A spreadsheet program which recognizes tab-delimited text files, such as Microsoft Excel, is recommended. Any word-processing program or Web browser will also display the data.

Data Acquisition and Processing


Section Sampling

Sampling was performed on sites approximately one quarter section (800 m by 800 m) in size. Three soil moisture samples were taken at 16 locations in a field. See more details in sections 1.1 and 2.1.1 of the SMAPVEX12 Database Report, released 18 December 2012.


Investigators used Stevens Hydra Probe II and Delta-T Devices ThetaProbe to measure surface volumetric soil moisture.

Hydra Probes

Hydra Probes are based on coaxial impedance dielectric reflectometry. The probes were connected to a PDA. They use an oscillator to generate an electromagnetic signal at 50 MHz that is propagated through three metal tines into the soil. The part of the signal that is reflected back to the unit is measured in volts and is used to numerically solve Maxwell's equations, to calculate the impedance and the real and imaginary dielectric permittivity.

Theta Probes

The Theta Probes have 4 separate 6-cm stainless steel rods inserted vertically into the soil. Each instrument was connected to a handheld reader, which delivers the electrical pulse, detects the return signal, and converts the period to a voltage between 0 V and about 1 V.

See the SMAPVEX12 Hydra and Theta Probe Calibration document, released 19 December 2012.

References and Related Publications

Alharthi, A., and J. Lange. 1987. Soil Water Saturation: Dielectric Determination. Water Resour. Res. 23:591-595.

Cosh, M. H, T. J. Jackson, R. Bindlish, J. S. Famiglietti, and D. Ryu. 2005. Calibration of an Impedance Probe for Estimation of Surface Soil Water Content over Large Regions.J. Hydrol. 311: 49-58.

Huang, Q., O. O. Akinremi, R. Sri Ranjan, and P. R. Bullock. 2004. Laboratory and Field Evaluation of Five Soil Water Sensors. Can. J. Soil Sci. 84:431-438

Ledieu, J., P. de Ridder, P. de Clerck, and S. Dautrebande. 1986. A Method of Measuring Soil Moisture by Time-Domain Reflectometry. J. Hydrol. 88:319-328.

Seyfried, M. S., and M. D. Murdock. 2004. Measurement of Soil Water Content with a 50-MHz Soil Dielectric Sensor. Soil Sci. Soc. Am. J. 68:394-403.

Seyfried, M. S., L. E. Grant, E. Du, and K. Humes. 2005. Dielectric Loss and Calibration of the Hydra Probe Soil Water Sensor. Vadose Zone J. 4:1070-1079.


Grant Wiseman
Science and Technology Branch
Agriculture and Agri-Food Canada
200-303 Main Street
Winnipeg, MB R3C 3G7, Canada
phone: +1 204.259.4006

Paul Bullock
Department of Soil Science
University of Manitoba
13 Freedman Crescent
Winnipeg, Manitoba R3T 2N2, Canada
phone: +1 204.474.8666

Aaron Berg
Department of Geography
University of Guelph
Guelph, ON, N1G 2W1, Canada
phone: +1 519.824.4120


Agriculture and Agri-Food Canada, National Aeronautics and Space Administration, U.S. Department of Agriculture, Environment Canada, U. Manitoba, U. Guelph, Massachusetts Institute of Technology, U. South Carolina, U. Colorado, U. Sherbrooke, Ohio State, U. Montana, Florida International U., U. Southern California, Texas A&M, Georgia Institute of Technology, U. Washington are acknowledged for their support for the campaign.

Field Sampling Team

Aaron Berg, University of Guelph
Alan Rich, University of Manitoba
Alicia Joseph, NASA GSFC
Alexandra Konings, MIT
Amine Merzouki, Agriculture and Agri-Food Canada
Bin Fang, U.S. Carolina
Brandon Wyryha, Agriculture and Agri-Food Canada
Brian Miller, University of Manitoba
Catherine Champagne, Agriculture and Agri-Food Canada
Craig Smith, Environment Canada
Christina Neva Rivera, Agriculture and Agri-Food Canada
Dominik Schneider, University of Colorado
Erika Podest, JPL
Erle Einarsson, Agriculture and Agri-Food Canada
Evan Rodgers, Agriculture and Agri-Food Canada
Grant Wiseman, Agriculture and Agri-Food Canada
Greg Gibbons, Agriculture and Agri-Food Canada
Heather McNairn, Agriculture and Agri-Food Canada
Hida Manns, University of Guelph
Hoda Jafarian, University of Sherbrooke
Jacqueline Freeman, Agriculture and Agri-Food Canada
Jeff Ouellette, Ohio State
Jennifer Watts, University of Montana
Jiali Shang, Agriculture and Agri-Food Canada
John Fitzmaurice, Agriculture and Agri-Food Canada
Jon Belanger, University of Guelph
Justin Adams, University of Guelph
Kalifa Goïta, University of Sherbrooke
Karel Janik, University of Sherbrooke
Kaighin McColl, MIT
Kurt Gottfried, Agriculture and Agri-Food Canada
Luis Perez, FIU - Florida International University
Marco Carrera, Environment Canada, Meteorological Research Division
Maria Abrahamowicz, Environment Canada
Mariko Burgin, University of Southern California
Maheshwari Neelman, Texas A&M
Matt Jones, University of Montana
Mehdi Hosseini, University of Sherbrooke
Mike Cosh, USDA, ARS Hydrology and Remote Sensing Laboratory
Mustafa Aksoy, Ohio State
Najib Djamai, University of Sherbrooke
Nandita Gaur, Texas A&M
Narendra Das, JPL
Parag Narvekar, MIT
Parinaz Rahimzadeh, University of Guelph
Patrick Rollin, Agriculture and Agri-Food Canada
Paul Bullock, University of Manitoba
Peggy O'Neill, NASA GSFC
Rachel Molloy, Agriculture and Agri-Food Canada
Rebecca Warren, University of Guelph
Rebecca Scriver, University of Guelph
Ramata Magagi, University of Sherbrooke
Robert Terwilleger, University of Florida
Rotimi Ojo, University of Manitoba
Ruzbeh Akbar, University of Southern California
Sab Kim, JPL
Sarah Banks, Agriculture and Agri-Food Canada
Sarah Dyck, Environment Canada
Saeid Homayouni, Agriculture and Agri-Food Canada
Shawna McKnight, Georgia Institute of Technology
Sonia Becenko, Agriculture and Agri-Food Canada
Stacie Westervelt, University of Manitoba
Steven Chan, JPL
Syed Anwar, Agriculture and Agri-Food Canada
Tien-Hoa Liao, University of Washington
Tracy Rowlandson, University of Guelph
Vanessa Escobar, NASA GSFC

Document Information


October 2013


February 2020

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