Data Set ID: 

SnowEx17 Ground Penetrating Radar, Version 1

This data set contains the results of a ground penetrating radar survey conducted at Grand Mesa, Colorado. Data include the two-way travel time, calculated snow depth, and calculated snow water equivalent. Data were collected between 08 February 2017 and 23 February 2017 as part of the 2017 SnowEx campaign.

The unprocessed, raw data can be found here:

There is a more recent version of these data.

Version Summary: 

new data set

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

See All Level of Service Details

  • SNOW/ICE > SNOW WATER EQUIVALENT > Snow Water Equivalent
Data Format(s):
  • ASCII Text
Spatial Coverage:
N: 39.11115, 
S: 38.9935, 
E: -107.85785, 
W: -108.22367
Spatial Resolution:Not applicableSensor(s):GPR
Temporal Coverage:
  • 8 February 2017 to 23 February 2017
Temporal ResolutionNot applicableMetadata XML:View Metadata Record
Data Contributor(s):Webb, R., D. McGrath, K. Hale, and N. P. Molotch.

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.

Webb, R., D. McGrath, K. Hale, and N. P. Molotch. 2018. SnowEx17 Ground Penetrating Radar, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: [Date Accessed].
20 July 2018
Last modified: 
16 August 2018

Data Description


Table 1. Parameters 
Parameter Description Units
Two-way travel time Time between the transmission of the ground penetrating radar (GPR) signal and the reflection of that signal back to the transmitting device nanoseconds, ns
Snow depth Calculated from two-way travel time, assuming a velocity of 0.234 m/ns meters, m
Snow water equivalent (SWE) Calculated from snow depth, assuming a density of 335 kg/m3 millimeters, mm

File Information


Data are provided in plain text (.txt) format. 

File Contents

Each plain text file includes 12 columns of data. Column titles and descriptions are shown below:

  1. COLLECTION_Date: Collection information in the format of GPR_[LineNumber]_[date], where:
  • Table 2. Column Definition 
    Variable Description
    GPR Short for ground penetrating radar
    [LineNumber] Value associated with the raw file
    [date] Date in mmddyy format
  1. TRACE: Trace number, corresponds to the raw data files. Each trace is the individual recording of a received signal from the GPR pulse.
  2. LONG: Longitude
  3. LAT: Latitude
  4. ELEV: Elevation, in meters (m)
  5. TWT: Two-way travel time, in nanoseconds (ns), of the interpreted ground surface reflection
  6. SNOW DEPTH: Snow depth, in meters (m)
  7. SWE: Snow water equivalent (SWE), in millimeters (mm)
  8. EASTING: Easting, calculated from the recorded longitude
  9. NORTHING: Northing, calculated form the recorded latitude
  10. UTM_ZONE: UTM grid zone for the calculated easting and northing
  11. TRANSECT: Transect number 

More details about column definitions can be found in the technical references.

Naming Convention

Data files utilize the following naming convention:


Table 3. File Naming Convention
Variable Description
SnowEx17_GPR Short name for SnowEx17 Ground Penetrating Radar
Week (1, 2, or 3) in which the data was collected
transects Items surveyed with the ground penetrating radar




File Size

Plain text files range in size from approximately 18.5 MB to 22.5 MB.

The total data set is approximately 60 MB.

Spatial Information


Data were collected in the Grand Mesa, Colorado study area:

Northernmost Latitude: 39.11115° N
Southernmost Latitude: 38.99350° N
Easternmost Longitude: 107.85785° W

Westernmost Longitude: 108.22367° W


Point measurements


All data falls within the project coordinate system WGS 84 / UTM Zone 12 North, details of which are presented in Table 4. 

Table 4. Geolocation Details
Geographic coordinate system WGS 84
Projected coordinate system WGS 84 / UTM Zone 12 North
Longitude of true origin -111
Latitude of true origin 0
Scale factor at longitude of true origin 0.9996
Datum WGS 1984
Ellipsoid/spheroid WGS 84
Units meters
False easting 500000
False northing 0
EPSG code 32612
PROJ4 string +proj=utm +zone=12 +datum=WGS84 +units=m +no_Defs

The plain text files indicate that all geographic coordinates fall within UTM Grid Zone 12S. This designation corresponds to the intersection of longitudinal projection zone 12 and latitudinal projection zone S, as shown in Figure 1. Users should be aware that UTM Grid Zone 12S falls within the projected coordinate system WGS 84 / UTM Zone 12 North. 
Figure 1: UTM Grid Zones

Temporal Information


08 February 2017 to 23 February 2017

Data collection was separated into three weeks:

  • Week 1: 08 February 2017 - 10 February 2017
  • Week 2: 14 February - 17 February 2017
  • Week 3: 21 February - 23 February 2017

Data Acquisition and Processing


Ground penetrating radar (GPR) surveys were conducted using a MALA Professional Explorer (ProEx) control unit and a shielded 1.6 GHz antenna. Both the MALA ProEx unit and antenna were pulled in a plastic sled behind users, who were on skis, snowshoes, or snowmobiles. Manual snow depth measurements were taken in parallel to GPR surveys but only used to estimate the two-way travel time velocity needed to calculate snow depth. 

Data were collected along transects at the Grand Mesa, Colorado study site. Transects were walked in their entirety, with some transects surveyed more than once (multiple days apart). When there was sufficient time available, grids were surveyed alongside individual transects to build a more robust dataset of directional spatial patterns. Additional grids corresponding to the locations of terrestrial lidar (light detection and ranging) scans were also surveyed for future comparisons.

Field notes are available as a technical reference.


Raw data files were processed in MALA RadExplorer and ReflexW2D software. Data were processed line by line for time-zero correction and background noise removal. In all instances, the ground surface was semi-automatically picked.

Snow depth (meters, m) was calculated from the two-way travel time by assuming a velocity of 0.234 m/ns. This assumption represents the average velocity calculated from comparisons between ground penetrating radar data and manual snow depth measurements. 

Snow Water Equivalent (millimeters, mm) was calculated from the estimated snow depth by assuming a density of 335 kg/m3. This assumed density was based on snow pit observations.

Quality, Errors, and Limitations

Uncertainty of snow depth is approximately 3.5 cm. 

A known source of error was that the GPR path along the transects and manual snow depth measurements did not always align precisely.



Data were collected using a MALA Professional Explorer (ProEx) control unit. More information about this instrument can be found on the manufacturers website.

Related Data Sets

Other SnowEx Data Sets

Related Websites


Contacts and Acknowledgments

Ryan Webb
Institute of Arctic and Alpine Research
University of Colorado - Boulder
4001 Discovery Drive, Rm N202

Boulder, CO 80309

Daniel McGrath
Department of Geosciences

Colorado State University

Katherine Hale

University of Colorado - Boulder

Noah Molotch
University of Colorado - Boulder

How To

Programmatic Data Access Guide
Data from the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC) can be accessed directly from our HTTPS file system or through our Application Programming Interface (API). Our API offers you the ability to order data using specific temporal and spatial filters... read more