What the dataset was used for: to estimate the change in vegetation amount over time in Wyoming. We used three Landsat Multi Spectral Scanner (MSS) images, one from the early-to-mid 1970s, one from the mid 1980s, and one from the early 1990s. Vegetation amount is determined from the Normalized Difference Vegetation Index, defined as (Band 4 - Band 2)/(Band 4 + Band 2), where Band 4 covers near-infrared (NIR) wavelengths from 0.8 to 1.1 Fm and Band 2 covers red wavelengths from 0.6 to 0.7 Fm. NDVI saturates with one-sided leaf area indices (LAI) of 4 and higher; however, this is not a problem for Wyoming grasslands and shrublands have low LAI. NDVI varies from -1 to 1, and are converted into digital numbers (DN) by: 100 (NDVI+1), so the DN varies from 0 to 200.
Change detection is estimated as the NDVI(1990) - 0.5[NDVI(1980) - NDVI(1970)] for each image, except for areas covered with snow, clouds, and shadows caused by clouds. If two dates were available for these areas, we subtracted the NDVI of the earlier date from the NDVI of the later date. The dates of acquisition were usually collected towards the end of the growing season, and usually during years of drought (for example: 1992, 1985, 1972). We have developed an algorithm using the Advanced Very High Resolution Radiometer (AVHRR) data from the EROS Data Center to adjust NDVIs to average precipitation amounts, but these corrections were not applied to this dataset.
The identification of features is provided by the distinct electromagnetic energy it emits, reflects, or otherwise transmits. This is called the spectral signature. Other signatures are tone (lightnes or darkness), texture (surface roughness or smoothness), pattern, shadow, shape and size are as important. Thus, through the use of multispectral scanners, such elements as water features, soils, and vegetation can be identified and distinguished from each other.
This accuracy statemend is taken from the USGS metadata for Landsat MSS:
The MSS sensor scanned the Earth's surface from west to east as the satellite moved in its descending (north-to-south) orbit over the sunlit side of the Earth. Six detectors for each spectral band provided six scan lines on each active scan. The combination of scanning geometry, satellite orbit, and Earth rotation produced the global coverage necessary for studying land surface change. The resolution of the MSS sensor was approximately 80 m with radiometric coverage in four spectral bands from the visible green to the near-infrared (IR) wavelengths. Only the MSS sensor on Landsat 3 had a fifth band in the thermal-IR.
Path 38 Row 29 (Yellowstone) 08/01/73, 08/02/86, 08/26/92 Path 37 Row 29 (Cody) 08/01/73, 08/27/86, 08/19/92 Path 36 Row 29 (Greybull) 07/25/74, 07/19/86, 07/27/92 Path 35 Row 29 (Sheridan) 09/17/74, 08/29/86, 08/29/92 Path 34 Row 29 (Sundance) 09/08/72, 09/17/84, 09/05/91 Path 38 Row 30 (Jackson) 08/15/74, 08/15/85, 08/26/92 Path 37 Row 30 (Pinedale) 08/06/72, 08/27/86, 08/27/92 Path 36 Row 30 (Riverton) 07/30/73, 07/19/86, 07/27/92 Path 35 Row 30 (Casper) 09/17/74, 10/16/86, 09/30/92 Path 34 Row 30 (Lusk) 09/08/72, 09/17/84, 09/21/91 Path 37 Row 31 (Fontenelle) 08/05/72, 08/08/85, 07/26/92 Path 36 Row 31 (Rock Springs) 08/05/72, 08/17/86, 08/12/92 Path 35 Row 31 (Rawlins) 07/01/75, 06/07/85, 06/02/92 Path 34 Row 31 (Laramie) 07/01/75, 07/02/85, 07/05/92 Path 33 Row 31 (Pine Bluffs) 08/19/72, 08/15/86, 08/15/92See the USGS metadata for Landsat MSS for more detailed description of collection and processing of the satellite imagery. <URL:http://edcwww.cr.usgs.gov/nsdi/html/landsat_mss/landsat_mss>
0 white (edges, no data) 1 black 2 - 72 red (large decrease in vegetation amount) 73 - 83 coral 84 - 94 yellow 95 - 105 thistle (no change) 106 - 116 green 117 - 127 cyan 128 - 255 blue (large increase in vegetation amount)There are also three-band false-color composite images showing the scene area. The three bands are MSS Band 4 (NIR) displayed as red, MSS Band 2 (red) displayed as green, and MSS Band 1 (green, 0.5 to 0.6 Fm wavelengths) displayed as blue. The dates for the false-color composite TIFF files are:
Yellowstone 08/26/92 Cody 08/19/92 Greybull 07/27/92 Sheridan 09/17/74 Sundance 09/05/91 Jackson 08/26/92 Pinedale 08/27/92 Riverton 09/30/92 Casper 09/30/92 Lusk 09/21/91 Fontenelle 07/26/92 Rock Springs 08/12/92 Rawlins 06/02/92 Laramie 07/01/75 Pine Bluffs 08/15/92