All imagery is in ERDAS Imagine format. If not specified in the file name, image resolution is 60 meters. Each sample may contain the following data:
- MSS, TM, ETM+ imagery
- 1992 MRLC data
- Final land cover images for all 5 decades, 30m & 60m versions for 1992 and 2000
- Change images between the four time intervals (four images total)
- Multiple change image showing the overall footprint of change
File name convention for imagery is samp<ecoregion>_<sample>_<date>_<sensor>.
Date is in the format mmddyy, except ecoregion 14 where only the year is used. In rare cases, images from two dates were required for complete coverage, usually due to cloud cover. Both dates are listed on the web page and included in the file names.
Sensors are Landsat Multi-Spectral Scanner (mss), Landsat Thematic Mapper (tm), Enhanced Thematic Mapper (etm) and panchromatic data from ETM+ (pan).
Convention for land cover images is samp<eco>_<sample>_<date>_lc_final.
Land cover codes are:
- Water (blue)
- Developed (red)
- Mechanical Disturbed/Transitional (magenta)
- Mining (black)
- Natural Barren (gray)
- Forest (green)
- Grassland/Shrubland (yellow)
- Agriculture (orange)
- Wetland (cyan)
- Non-Mechanical Disturbed/Transitional (purple)
- Snow/Ice (white)
Change image codes are sequential, so 1 = change from class 1 to class 1, 2 = change from class 1 to class 2, 3 = change from class 1 to class 3, etc. Since the number of classes varies by ecoregion and sample, the codes will also vary. For example, if there are eight classes, then 9 = change from class 2 to class 1, but if there are nine classes, 9 = change from class 1 to class 9.
Multi change images codes are 0 to 4, representing the number of times the land cover in the pixel changed.
“Sliver” samples – In a very few cases, there was not enough land area in the sample block to derive statistically significant classification accuracies. In these cases, an adjacent sample was selected, and imagery from both samples was classified. Since the samples were treated as one entity, data for both samples are listed on the same page and can be accessed by clicking either sample in the map.
Samples that include area from multiple ecoregions - Where a sample contained
area from more than one ecoregion, the land cover and change images depict
the entire sample block, not just the portion inside the ecoregion of
interest. The excel spreadsheet for these samples also represent information
for the entire block.