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Data Set ID:
NSIDC-0188

SMEX02 Regional Vegetation Sampling Data, Iowa, Version 1

This data set contains the vegetation parameters plant height, row spacing, stand density, and leaf area index (LAI) as part of the Soil Moisture Experiment 2002 (SMEX02).

This is the most recent version of these data.

Parameter(s):
  • Agricultural Plant Science
  • Vegetation > Leaf Characteristics
  • Vegetation > Plant Characteristics
  • Plants
  • Plant Commodities > Vegetable Products
  • Vegetation
  • Vegetation > Vegetation Cover
  • Vegetation > Vegetation Index
  • Vegetation > Vegetation Species
Data Format(s):
  • ASCII Text
Spatial Coverage:
N: 42.7, 
S: 41.7, 
E: -93.2, 
W: -93.8
Platform(s):FIELD SURVEYS
Spatial Resolution:Not SpecifiedSensor(s):LICOR PLANT CANOPY ANALYZER
Temporal Coverage:
  • 30 June 2002 to 28 July 2002
Version(s):V1
Temporal ResolutionNot specifiedMetadata XML:View Metadata Record
Data Contributor(s):Martha Anderson

Geographic Coverage

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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.

Anderson, M. 2003. SMEX02 Regional Vegetation Sampling Data, Iowa, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/0Q8WOQ3RC8DQ. [Date Accessed].

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Detailed Data Description

Format

Data are provided as ASCII text files.

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File Naming Convention

"IA_LAI_Raw.txt" contains the raw data; "IA_LAI_Sum.txt" contains the summary data.

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File Size

File sizes are: "IA_LAI_Raw.txt" 16.0 KB, and "IA_LAI_Sum.txt" 3.76 KB.

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Volume

Total volume of the data files is 19.76 KB.

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Spatial Coverage

Southernmost Latitude: 41.7° N
Northernmost Latitude: 42.7° N
Westernmost Longitude: 93.8° W
Easternmost Longitude: 93.2° W

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Temporal Coverage

Dates for sampling were 29 and 30 June, and 3, 9, 28, and 29 July 2002.

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Parameter or Variable

Parameter Description

The parameters are plant height, row spacing, stand density, and leaf area index (LAI).

The following table describes each column in the "IA_LAI_Raw.txt" data file.

Column heading Description
SITE Site location number
SAMPLE Sampling point 1-5 for each site location
Latitude Latitude of the sampling site
Longitude Longitude of the sampling site
UTM_East UTM Easting in meters (Zone 15)
UTM_North UTM Northing in meters (Zone 15)
LAI Leaf Area Index
Date MM/DD/YYYY
DAY Numerical day of the year (Julian date)
Time HHMMSS (Central Standard Time)
Adjusted Readings corrupted by sun glare were adjusted by an interpolated estimate

The following table describes each column in the "IA_LAI_Sum.txt" data file.

Column heading Description
SITE Site location number
Latitude Latitude of the sampling site
Longitude Longitude of the sampling site
UTM_East UTM Easting in meters (Zone 15)
UTM_North UTM Northing in meters (Zone 15)
DOY Numerical day of the year (Julian date)
date MM/DD/YYYY
LAI-Mean Mean Leaf Area Index
LAI-StDev Standard deviation of Leaf Area Index
Crop C=Corn, S=Soy
Row_Spacing in m Space between rows in meters
Row_Density Number of plants in one meter
Height in m Vegetation height in meters

Unit of Measurement

  • LAI - The ratio of the area of the upper side of the leaves projected onto a flat surface to the area of the surface.
  • Row spacing - The distance in meters between the center of one plant row to the center of the next crop row.
  • Row density - The number of plants in one meter within a row.
  • Height - The height of the upper leaves in a crop row.

Parameter Source

LAI is measured by a plant canopy analyzer. Row spacing, row density, and plant height were measured manually.

Sample Data Record

The following sample is taken from the "IA_LAI_Raw.txt" data file.

SITE SAMPLE Latitude Longitude UTM_East UTM_North LAI Date DOY TIME Adjusted
IA01 1 42.65988 -93.71737 441207 4723296 2.45 6/30/2002 181 11:53:30 **
IA01 2 42.65988 -93.71737 441207 4723296 2.71 6/30/2002 181 11:55:24 **
IA01 3 42.65988 -93.71737 441207 4723296 1.87 6/30/2002 181 11:57:01
IA01 4 42.65988 -93.71737 441207 4723296 2.06 6/30/2002 181 11:58:21

The next sample is taken from the "IA_LAI_Sum.txt" data file.

SITE Latitude Longitude UTM_East UTM_North DOY date LAI-Mean LAI-StDev Crop Row_Spacing in m Row_Density Height in m
IA01 42.65988 -93.71737 441207 4723296 181 6/30/2002 2.252 0.023 C 0.75 7 1.524
IA02 42.58718 -93.70582 442086 4715215 181 6/30/2002 2.612 0.034 C 0.75 7 2.1336
IA03 42.50662 -93.71921 440911 4706278 181 6/30/2002 1.29 0.072 S 0.75 30 0.381
IA04 42.41222 -93.72801 440099 4695803 181 6/30/2002 2.39 0.089 C 0.75 6 1.524
IA05 42.34171 -93.72867 439977 4687974 181 6/30/2002 1.398 0.025 C 0.75 6 1.397
 
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Software and Tools

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Data Acquisition and Processing

Theory of Measurements

The purpose of vegetative sampling is to provide an estimate of the variation in the vegetative components in the corn and soybean fields across the SMEX02 study sites. Sampling dates are provided in the data files for each field.

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Data Acquisition Methods

Five locations were sampled in each field in the IA regional soil moisture sampling site. Samplers chose locations far enough away from each other to gain independent samples. At each location, leaf area was measured at four locations (in-row, ¼ across row, ½ across row, ¾ across row) with the plant canopy analyzer. The first sampling position was between the first row and the row to the left.

Leaf area was measured in the inter-row region at least one meter away from where the manual samples were taken. The analyzer was set to average four locations into a single value, so one observation was taken above the canopy and four beneath the canopy; in the row, ¼ of the way across the row, ½ of the way across the row, and ¾ of the way across the row. This gave a good spatial average for row crops of partial cover. The sampler always stood with the back to the sun (if it was shining). A lens cap that blocks ¼ of the sensor view was always in place and positioned so the sun and the sampler were never in the view of the sensor.

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Derivation Techniques and Algorithms

Error Sources

In the final processing, certain LAI readings were determined to have been corrupted by sun glare. These readings were adjusted or recovered by replacing an interpolated estimate. This was done for approximately 36 of the 236 readings, and one reading was determined to be too corrupted to adjust. A value of "-99" indicates missing or corrupt data.

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Sensor or Instrument Description

LAI sampling was done using LI-COR LAI-2000 instruments.

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References and Related Publications

Please see the SMEX02 site for more information, and the NSIDC SMEX site to access data.

Contacts and Acknowledgments

Martha Anderson
Assistant Scientist
Space Science and Engineering Center
University of Wisconsin, Madison, WI, USA.

Acknowledgments: 

Many graduate students and volunteers collected the field data.

Document Information

DOCUMENT CREATION DATE

September 2003

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