Landsat Geometric Verify Image and Report
The Landsat Geometric Verify Image and Report files are provided in Landsat 1-5 Multispectral Scanner (MSS) and Landsat 4-5 Thematic Mapper (TM) Tier 1 Level-1 products.
The Verify Image file (_VER.jpg) displays a colored grid of verification points to represent the accuracy of geometric correction, using cross-correlation techniques to compare the product to the GLS 2000 reference dataset (see image below). This graphical representation of the Geometric Verify Report (_VER.txt) helps users determine the geometric accuracy of each MSS and TM precision and terrain-corrected scene. The Verify Report contains summary statistics and lists all verification points.
The Root Mean Square Error (RMSE) associated with the Verify Image product is calculated using measurements performed at locations shown by gradient dots. The intent of the verify product is to provide quadrant and full image estimates to quantify the accuracy of the product, as well as to provide a visual representation of the spatial distribution of errors throughout the image. Users should carefully note the distribution of the measurements. In areas where there are no measurements (i.e. a deviation from a regular grid), accuracy assessments could not be made. Possible reasons for this include the presence of clouds, absence of texture (persistent edges such as roads, rivers, fields, boundaries, ridgelines), and so forth. If the same features cannot be found on the reference image and the product or if contrast within the image is low, then correlation errors may occur.
| Legend | |
|---|---|
| Color | RMSE |
| Green | <= 0.5 pixel |
| Cyan | 0.5 pixel to <= 1 pixel |
| Blue | 1 pixel to <= 2 pixel |
| Yellow | 2 pixel to <= 3 pixel |
| Red | > 3 pixel |
| RMSE by Quadrant and Scene | |
| Upper Left | 0.33 pixel |
| Upper Right | 0.41 pixel |
| Lower Right | 0.43 pixel |
| Lower Left | 0.44 pixel |
| SCENE | 0.41 pixel |
Rules of Image: 50x50 grid, strength of correlation, distance from other points, RMSE.