BOREAS HYD-06 Ground Gravimetric Soil Moisture Data
Summary:
This data set contains percent soil moisture ground measurements. These data
were collected on the ground along the various flight lines flown in the
Southern and Northern Study Areas (SSA and NSA) during 1994 by the gamma ray
instrument. The data are available in tabular ASCII files.
Table of Contents
* 1 Data Set Overview
* 2 Investigator(s)
* 3 Theory of Measurements
* 4 Equipment
* 5 Data Acquisition Methods
* 6 Observations
* 7 Data Description
* 8 Data Organization
* 9 Data Manipulations
* 10 Errors
* 11 Notes
* 12 Application of the Data Set
* 13 Future Modifications and Plans
* 14 Software
* 15 Data Access
* 16 Output Products and Availability
* 17 References
* 18 Glossary of Terms
* 19 List of Acronyms
* 20 Document Information
1. Data Set Overview
1.1 Data Set Identification
BOREAS HYD-06 Ground Gravimetric Soil Moisture Data
1.2 Data Set Introduction
This data set contains information on the locations of field in-situ measurement
sites along BOREAS flight lines with ground measurements of soil moisture, depth
of moss/humus layer, and water content of the moss/humus layer and contains
information on soil conditions and vegetative cover around the sites.
1.3 Objective/Purpose
The objectives of this research were: 1) to obtain improved estimates of the
soil moisture (SM) conditions for the BOREAS experimental areas, 2) to develop
techniques for measuring the water content (WC) of the moss/humus layer, 3), to
provide assistance to HYD-04 to measure the water equivalent (WE) of the snow
cover, 4) to provide information for validating and calibrating other remote
sensing methods, and 5) to provide information on the SM of the mineral soil,
the WC of the Moss/Humus layer, and the WE of the snow cover to other
investigators.
1.4 Summary of Parameters
This data set contains information (flight line identifiers, sample identifiers,
latitudes and longitudes) on the locations of ground sampling sites at which
measurements of the soil moisture of the mineral soil were obtained. In
addition to the data on the samples collected for computing the soil mositure of
the mineral soil, brief information on the vegetation are included for those
sites where measurements were made by members of HYD-04. For locations where
measurements of the soil moisture of the mineral soil were made by members of
HYD-06, detailed information on the terrain, the vegetative cover and on soil
conditions are contained in this data set.
1.5 Discussion
As part of the BOREAS experiment, natural terrestrial gamma radiation data over
a network of 48 flight lines were collected. For each of these flight lines,
ground in-situ SM measurements of the mineral soil and WC of the moss/humus
layer were collected and used, along with other available measurements, to
establish one-time calibration of the natural terrestrial radioisotope signal
over the flight line network.
1.6 Related Data Sets
BOREAS HYD-06 Aircraft Gamma Ray Soil Moisture Data
BOREAS HYD-06 Moss/Humus Moisture Data
2. Investigator(s)
2.1 Investigator(s) Name and Title
Dr. Eugene L. Peck
Hydex Corporation
Dr. Thomas Carroll
National Weather Service
2.2 Title of Investigation
Remote Sensing of Hydrologic Variables in Boreal Areas
2.3 Contact Information
Contact 1
--------------
Dr. Eugene L. Peck
Hydex Corporation
Vienna, VA
(703) 281-6284
(703) 281-7014
genepeck@aol.com
Contact 2
--------------
Dr. Thomas Carroll
NOHRSC, Office of Hydrology
NWS, NOAA
Chanhassen, MN
(612) 361-6610, ext. 225
(612) 361-6634
tc@nohrsc.nws.gov
3. Theory of Measurements
In-situ ground samples of the SM of the mineral soil and of the WC of the
moss/humus layer are obtained using the gravimetric method (percent by weight of
dry soil). The soil and moss/humus layer samples are placed in plastic
containers and are later dried out for 24 hours in an drying oven at 105 degrees
centigrade.
4. Equipment:
4.1 Sensor/Instrument Description
A soil sampler with a 2.54 cm2 orifice is used to collect the sample of the
mineral soil to a depth of 20 cm, where possible. An ESC-30 (Eastern Snow
Conference) snow tube having an orifice of 30 cm2 is used to collect samples of
the moss/humus layer. Depth of the moss/humus layer are measured by a ruler
after digging down to the mineral soil.
4.1.1 Collection Environment
Northern and Southern Study Areas (NSA and SSA).
The airborne and ground measurements of soil moisture and moss/humus were
planned the evening before each days surveying. The airborne and ground
measurements were taken simultaneously as much as possible. Ground measurement
for calibration purposes were obtained when the flight line areas were fairly
dry and never during rain occurrence.
4.1.2 Source/Platform
Human.
4.1.3 Source/Platform Mission Objectives
To collect cores of soil and moss/humus at various locations.
4.1.4 Key Variables
Soil and Moss/Humus moisture content.
4.1.5 Principles of Operation
Unknown.
4.1.6 Sensor/Instrument Measurement Geometry
A soil sampler with a 2.54 cm2 orifice is used to collect the sample of the
mineral soil to a depth of 20 cm, where possible.
An ESC-30 snow tube having an orifice of 30 cm2 is used to collect samples of
the moss/humus layer
4.1.7 Manufacturer of Sensor/Instrument
Unknown.
4.2 Calibration
Unknown.
4.2.1 Specifications
Unknown.
4.2.1.1 Tolerance
Unknown.
4.2.2 Frequency of Calibration
Unknown.
4.2.3 Other Calibration Information
Unknown.
5. Data Acquisition Methods
Ground measurements were collected at over 1100 locations along 42 of the 48
BOREAS airborne gamma radiation flight lines during the field experiments. Maps
showing locations of most BOREAS established flight lines are shown on Figures
5.2.1.4a, 5.2.1.4b 5.2.1.4c, and 5.2.1.4c of version 3.0 of the BOREAS
Experimental Plan. Revised computerized maps of all of the 48 flight lines
prepared by NOHRSC (March 1995) are available in BORIS (containing a few
additional lines that were established during the field experiments).
The flight lines are numbered BP100 to BP123 and CR954 to CR960 in the southern
research area (SSA) and BP201 to BP213 in the northern study area (NSA). Flight
lines BP301 to BP305 are located along the transect between the SSA and NSA.
The CR lines in the SSA are part of the operational snow measurement program of
the Atmospheric Environment Service, AES, of Canada.
6. Observations
6.1 Data Notes
None.
6.2 Field Notes
Field notes for the ground sampling of the SM of the mineral soil and the WC of
the moss/humus layer by members of HYD-06 and HYD-04 during non-snow periods are
contained in the data itself. Ground samples of the water equivalent of the
snow cover and other measurements obtained during the 1993 and 1994 IFC-Ws are
being placed in BORIS by HYD-04.
Ground measurements were collected during September 1993 for a proposed north-
south flight line on the western side of the highway directly east of the Young
Jackpine and Fen towers sites in the SSA. Ground and airborne observations
clearly indicated that the vegetation over the area to be measured by the
airborne gamma surveys was highly variable, so much so that any reasonable
number of measurements could not provide acceptable information on average
conditions along the flight line. Information collected for this proposed line
are listed under flight line BP140 in the file Mastergd.DAT.
7. Data Description
7.1 Spatial Characteristics
The two BOREAS study areas are located with a large area of interest covering
over a million square kilometers in the Canadian Provinces of Saskatchewan (SSA)
and Manitoba (NSA). Each of the study areas are approximately 50 by 100 km.
The data that provides the locations of the various flight lines are described
in the HYD-6 Airborne Estimate of Soil Moisture document.
7.1.1 Spatial Coverage
These soil moisture measurements were made on the ground at various point
locations within the NSA and SSA.
There is a reference table called HYD06_TRANSECT_REF that contains
information about the location of the various flight lines.
NSA Spatial Coverage (North American Datum 1983 (NAD83))
Longitude Latitude
--------- -------
Upper Left -98.82 56.247
Upper Right -97.24 56.081
Lower Right -97.49 55.377
Lower Left -99.05 55.54
SSA Spatial Coverage
Longitude Latitude
--------- --------
Upper Left -106.23 54.319
Upper Right -104.24 54.223
Lower Right -104.37 53.419
Lower Left -106.32 53.513
7.1.2 Spatial Coverage Map
Not available.
7.1.3 Spatial Resolution
The ground samples of soil and moss/humus were made at point locations
throughout the NSA and SSA.
7.1.4 Projection
Not applicable.
7.1.5 Grid Description
Not applicable.
7.2 Temporal Characteristics
7.2.1 Temporal Coverage
The data was collected for as many flight lines as possible during the following
periods:
8 - 11 September 1993 (over SSA)
7 - 11 February 1994, IFC-W in cooperation with HYD-04 (over SSA and NSA)
24 July to 5 August 1944, IFC-2, (over SSA and NSA), and
30 August to 10 September 1994, IFC-3, (over SSA)
7.2.2 Temporal Coverage Map
Not available.
7.2.3 Temporal Resolution
Ground samples were collected on a daily basis. For most of the flight lines
the times the ground samples were obtained are included in the file
Mastergd.DAT. Times of sampling were not noted for those collected by members
of HYD-04
7.3 Data Characteristics
Data characteristics are defined in the companion data definition file
(h06grsmd.def).
7.4 Sample Data Record
Sample data format shown in the companion data definition file (h06grsmd.def).
8. Data Organization
8.1 Data Granularity
All of the Ground Gravimetric Soil Moisture Data are contained in one dataset.
8.2 Data Format(s)
The data files contain numerical and character fields of varying length
separated by commas. The character fields are enclosed with a single apostrophe
marks. There are no spaces between the fields. Sample data records are shown in
the companion data definition files (h06grsmd.def).
9. Data Manipulations
9.1 Formulae
None.
9.1.1 Derivation Techniques and Algorithms
None.
9.2 Data Processing Sequence
The soil samples in the sealed plastic containers obtained in the field are
weighed (total weight), the lids are removed, and the samples are dried in ovens
and weighed again (dry weight). The weight of the water is determined by
subtracting the dry weight and the weight of an average plastic lid for that day
from the total weight. The weight of the plastic lids and the plastic
containers vary from shipment to shipment and the average weights of those being
used each day are recorded on the laboratory form with the total and dry
weights. The weight of the soil for the sample is computed by subtracting the
average weight of the plastic container from the dry weight of the sample. The
SM of the mineral soil is the weight of the water divided by the weight of the
soil (percent of dry soil by weight).
Samples processed by members of HYD-04 are sealed and taken to AES offices in
Downsview, Ontario for processing.
9.2.1 Processing Steps
BORIS processed the data by:
1) Reviewing the initial data files and loading them on-line for BOREAS team
access,
2) Designing relational data base tables to inventory and store the data
3) Loading the the data into the relational data base tables,
4) Performing the following conversions on measurements into System
International (SI) units.
4) Working with the HYD-06 team to document the data set, and
5) Extracting the standardized data into logical files.
9.2.2 Processing Changes
None.
9.3 Calculations
9.3.1 Special Corrections/Adjustments
None.
9.3.2 Calculated Variables
None.
9.4 Graphs and Plots
Maps of the BOREAS flight lines, digitized by NOHRSC, are in BORIS. Maps are
also in the BOREAS Experiment Plan (version 3.0) (Figures 5.2.1.4a, 5.2.1.4b
5.2.1.4c, and 5.2.1.4c).
10. Errors
10.1 Sources of Error
Errors in determining the SM of the mineral soil (and the WC of the moss/humus
layer) are introduced by non-representative samples of the mineral soil (or of
the moss/humus layer). These may be caused by incorrectly introducing the
sampler into the soil, rocks in the soil preventing inserting the sampling tube
to the desire depth, and by not cleaning off the soil between samples. The
ability to remove a sample from the soil without disturbing the sample within
the tube is related to the experience of the observer.
10.2 Quality Assessment
10.2.1 Data Validation by Source
Confidence in the soil moisture in-situ measurement depends on many factors
regarding the accuracy of locating the sampling points along flight line as well
as the experience and training of the field personnel.
10.2.2 Confidence Level/Accuracy Judgement
The confidence level of the SM measurements varies with the experience of the
person selecting the flight line or locating the sampling sites on a map. In
very flat areas, the exact location of a ground measurement is difficult to
identify than for a site near a stream or in areas of variable terrain.
10.2.3 Measurement Error for Parameters
A precise estimate of the error of a SM measurement of the mineral soil can not
be determined. The selection of sites for in-situ measurements of the SM and
the WC of the moss/humus layer along a flight line is very critical During the
development of the airborne system in the United States it was clear that using
a grid method to collect soil moisture samples over farm land in Minnesota was
not viable. One or more measurements taken in shallow, low ravines, subject to
high soil moisture following periods of runoff producing precipitation would
result in unrepresentative average soil moisture values for sections of farm
land. Averages of these values would not correlate with the airborne estimates.
In Minnesota soil moisture observations of average land slope, generally one to
two percent, of corn fields and other crops were found to be best correlated
with airborne measurements.
Experience with the airborne gamma radiation system during the recent field
experiments First ISLSCP Field Experiment (FIFE) in Kansas (Carroll, et. al,
1988) illustrates the need to obtain ground measurements representative of the
average of the area from which ground based gamma are received by the airborne
detectors. During FIFE a few lines were established in areas where permission
to traverse all of the line on foot was not possible. Airborne estimates for
days without ground truth measurements showed that the estimated values tend to
be reasonable when the average soil moisture of the future flight was
approximately equal to that computed during calibration. However, during
periods when the average soil moisture departs significantly, either high or
low, from the calibration average, the estimates of the total soil moisture for
one or more bins along the line often appear to be exceptionally high or low.
During the BOREAS field experiments careful attention has been given to
obtaining as representative measurements of in-situ soil moisture along the
flight lines as possible. Most of the originally established flight lines were
located over areas having as consistent vegetative cover as possible (i.e., all
Old Aspen). However, in some areas, due to heterogenous conditions, it was not
possible to judge what measurements would provide representative averages. When
the flight and bins estimates are consistently in line with other measurements,
for all ranges of conditions, it is clear that the calibration of the line was
representative. The calibration of most, but not all, of the flight lines in
the SSA appear to be reliable and the soil moisture estimates are considered to
be very representative. The experience of the person selecting the in-situ
sites and the consistency of the vegetative cover are the two most important
factors for obtaining representative calibration of the flight lines.
10.2.4 Additional Quality Assessments
All of the airborne estimates are, or in the process of being, checked by
comparison with available SM and WC measurements along the same and nearby
flight lines. As additional SM and WC values become available a second level of
quality control will be accomplished by comparing the revised ground records
with airborne measurements.
10.2.5 Data Verification by Data Center
11. Notes
11.1 Limitations of the Data
None given.
11.2 Known Problems with the Data
Experience with the airborne gamma radiation system during the recent field
experiments First ISLSCP Field Experiment (FIFE) in Kansas (Carroll, et. al,
1988) illustrates the need to obtain ground measurements representative of the
average of the area from which ground based gamma are received by the airborne
detectors. During FIFE a few lines were established in areas where permission
to traverse all of the line on foot was not possible. Airborne estimates for
days without ground truth measurements showed that the estimated values tend to
be reasonable when the average soil moisture of the future flight was
approximately equal to that computed during calibration. However, during
periods when the average soil moisture departs significantly, either high or
low, from the calibration average, the estimates of the total soil moisture for
one or more bins along the line often appear to be exceptionally high or low.
11.3 Usage Guidance
The airborne gamma radiation soil moisture estimates of the total soil moisture
are only representative of average conditions along the flight line.
Considerable change in soil conditions may be found, even for lines having
nearly consistent vegetative cover. Careful review of the soil and vegetative
conditions are necessary to transfer the soil moisture estimates to nearby
areas. However, the use of the airborne estimates for similar conditions for
flux analyses and other studies can add considerable information on the spatial
and temporal variation in the SM of the mineral soil and of the WC of the
moss/humus layer.
11.4 Other Relevant Information
Ground measurements in file Mastermh.DAT (and in Mastergd.DAT) collected by
members of HYD-06 are collected under slightly different methods than those
collected by members of HYD-04. Those observed by members of HYD-04 do not show
times of observations.
Members of HYD-04 follow sampling procedures established for the operational
airborne gamma radiation snow surveys that have been collected in the BOREAS
area for many years, Sampling points are selected on a set distance from the
beginning of the flight line (either at one km or two km intervals depending on
the length of the flight line). This approach has proven useful for the
operational snow measuring program. Using this approach the measurement sites
are selected at nearly the same location along the flight line during snow and
non-snow periods. Members of HYD-06 collect only during non snow periods and
select measurements sites that tend to best represent the average conditions
along the entire 300 m wide foot path of the area measured by the airborne gamma
radiation surveys.
12. Application of the Data Set
None given.
13. Future Modifications and Plans
None.
14. Software
14.1 Software Description
None given.
14.2 Software Access
None given.
15. Data Access
15.1 Contact Information
Primary contact:
Ms. Beth McCowan
BOREAS Information System
NASA Goddard Space Flight Center
Greenbelt, Maryland
(301) 286-4005
(301) 286-0239
beth@ltpmail.gsfc.nasa.gov
15.2 Data Center Identification
See 15.1
15.3 Procedures for Obtaining Data
Users may place requests by telephone, electronic mail, or FAX.
15.4 Data Center Status/Plans
The HYD-06 ground soil moisture data are available from the EOSDIS ORNL DAAC
(Earth Observing System Data and Information System) (Oak Ridge National
Laboratory) (Distributed Active Archive Center).
The BOREAS contact at ORNL is:
ORNL DAAC User Services
Oak Ridge National Laboratory
(865) 241-3952
ornldaac@ornl.gov
ornl@eos.nasa.gov
16. Output Products and Availability
16.1 Tape Products
Gamma Ray site reference could be made available on 6250 or 1600 BPI computer
compatible tapes (CCT).
16.2 Film Products
Video tapes taken over each flight line during calibration showing the area
directly under the aircraft are available (at NOHRSC). At the present time no
decision has been made on storing these tapes in BORIS.
16.3 Other Products
Maps showing the flight lines for which Gamma data have been digitized and
submitted to BORIS by NOHRSC.
The data are available in tabular ASCII files.
17. References
Carroll, T. R., E. L. Peck, and D.M. Lipinski. 1988. Airborne time-series
measurements of soil moisture using terrestrial gamma radiation. Proc.Ann. Conf.
Am. Soc. Photogram. Remote Sens., St. Louis, MO.
17.1 Platform/Sensor/Instrument/Data Processing Documentation
17.2 Journal Articles and Study Reports
Sellers, P., F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan.
Version 1994-3.0, NASA BOREAS Report
(EXPLAN 94).
Sellers, P., F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan.
Version 1996-2.0, NASA BOREAS Report
(EXPLAN 96).
Sellers, P., F. Hall, K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study:
1994 Operations. NASA BOREAS Report (OPS
DOC 94).
Sellers, P., F. Hall, K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study:
1996 Operations. NASA BOREAS Report (OPS
DOC 96).
Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J.
Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J.
Ranson, D. Lettenmaier, and D.E. Wickland. 1995. The boreal ecosystem-atmosphere
study (BOREAS): an overview and early
results from the 1994 field year. Bulletin of the American Meteorological
Society. 76(9):1549-1577.
Sellers, P., F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue (in press).
17.3 Archive/DBMS Usage Documentation
None.
18. Glossary of Terms
None.
19. List of Acronyms
AES - Atmospheric Environment Service of Canada
BOREAS - BOReal Ecosystem-Atmosphere Study
BORIS - BOREAS Information System
BPI - Byte per inch
CCT - Computer Compatible Tape
CD-ROM - Compact Disk (optical), Read-Only Memory
DAAC - Distributed Active Archive Center
EOS - Earth Observing System
EOSDIS - EOS Data and Information System
ESC - Eastern Snow Conference
EXP - Experiment
FIFE - First ISLSCP Field Experiment
FIS - FIFE Information System (NASA)
GMT - Greenwich Mean Time
GPS - Ground positioning system
GSFC - Goddard Space Flight Center
HYD-04 - Group 4, BOREAS Hydrology science team
HYD-06 - Group 6, BOREAS Hydrology science team
ISLSCP - International Satellite Land Surface Climatology Project
Mev - Million Electronic Volts
NAD27 - North American datum of 1927
NAD83 - North American datum of 1983
NASA - National Aeronautics and Space Administration
NOHRSC - National Operational Hydrologic Remote Sensing Center
NSA - Boreas northern study area
NWS - National Weather Service
ORNL - Oak Ridge National Laboratory
SM - Soil moisture, percent by weight, of the mineral soil
SSA - Boreas sourthern study area
URL - Uniform Resource Locator
USGS - U. S. Geological Survey
WC - Water content of the moss/humus layer
WE - Water equivalent of the snow layer
20. Document Information
20.1 Document Revision Date
Written: 8-Jun-1995
Last Updated: 26-Feb-1998
20.2 Document Review Dates
BORIS Review: 07-Nov-1997
Science Review: 12-Dec-97
20.3 Document ID
20.4 Citation
Eugene L. Peck, President, Hydex Corporation
Thomas Carroll, Chief, NOHRSC
20.5 Document Curator
20.6 Document URL
Keywords
SOIL MOISTURE
MOSS MOISTURE
HYD06_GRNDSM.doc
Page 1 of 14
04/17/98