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Question:

What are the _VER.jpg and _VER.txt files that are included with the MSS and TM data I downloaded, and how can I use them?

Answer:

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. This graphic representation of the Geometric Verify Report (_VER.txt) assists users in determining the geometric accuracy of each MSS and TM precision- and terrain-corrected scene.

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.

Path/Row: 36/37 (WRS-1)

Path/Row: 36/37 (WRS-1)

Legend:
Green - RMSE <= 0.5 pixel
Cyan - 0.5 pixel < RMSE <= 1 pixel
Blue - 1 pixel < RMSE <= 2 pixel
Yellow - 2 pixel < RMSE <= 3 pixel
Red - RMSE > 3 pixel

RMSE by quadrant and scene
UL: 0.33 pixel
UR: 0.41 pixel
LR: 0.43 pixel
LL: 0.44 pixel
SCENE: 0.41 pixel
stored in metadata file (MTL)

Rules
50 by 50 grid
Strength of correlation
Distance from other points
RMSE

Verification report contains
summary statistics and a list of all
verification points.