Wyoming Vegetation Change Analysis from Landsat MSS Triplicates

Wyoming's long-term vegetation change is assessed using three Landsat Multi Spectral Scanner (MSS) satellite images from the early-to-mid 1970s, mid-1980s, and early 1990s. The dataset, created by SCIOPS, provides 15 geometrically corrected scenes covering the entire state, with vegetation amount derived from the Normalized Difference Vegetation Index (NDVI). Data acquisition typically occurred at the end of growing seasons, often during drought years like 1972, 1985, and 1992.

Use Cases

• Model vegetation change over two decades using the derived NDVI(1990) - 0.5[NDVI(1980) - NDVI(1970)] metric for each 60m pixel.
• Analyze the spatial distribution of vegetation health by mapping the digital number (DN) values, which range from 0 to 200 and correspond to NDVI.
• Study the impact of historical drought periods on grasslands by correlating acquisition dates (e.g., 1992, 1985, 1972) with NDVI values.
• Perform geospatial analysis on 15 scenes with a 185km by 170km footprint, corrected to a UTM projection at a 1:100,000 map scale.
• Investigate spectral reflectance in near-infrared (Band 4) and red (Band 2) wavelengths to calculate the foundational NDVI index for each time period.

Strengths

• Provides triplicate temporal snapshots spanning approximately 20 years for change detection.
• Offers complete spatial coverage of Wyoming with 15 satellite scenes.
• Data is geometrically corrected to a UTM projection at a 1:100,000 map scale for analysis readiness.
• Includes a derived change of NDVI product alongside the core image data.

Limitations

• Temporal coverage ends in the early 1990s, limiting analysis to historical trends before modern climate shifts.
• NDVI values are known to saturate for areas with high leaf area indices, though this is noted as less problematic for Wyoming's low-LAI landscapes.
• Areas covered by snow, clouds, and cloud shadows were excluded from the primary change detection calculation, potentially creating data gaps.

Provenance

Source

NASA Earthdata (North American Landscape Characterization Landsat MSS Triplicates), organization SCIOPS.

Collection Method

Derived from Landsat Multi Spectral Scanner (MSS) satellite imagery, resampled to 60m resolution and geometrically corrected.

Time Range

Early-to-mid 1970s, mid-1980s, and early 1990s.

Freshness

Historical dataset with a last updated date of 1992-12-31.

Geography

Complete coverage for the state of Wyoming, USA.