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The above image provides some insight into the nature of the relationship between the 30 meter (or 7.5-minute DEM) and 90 meter (or 3 arc-second DEM) data. This image shows the difference between the 7.5' data and the 3 arc-second data for each cell in the study area. White regions have very low or zero difference. As the difference becomes increasingly negative (meaning that the 3 arc-second value is greater than the 7.5' value) the cell color shades to blue . As the difference becomes increasingly positive (meaning that the 7.5' elevation value is greater than the 3 arc-second value) the cell color shades towards red.
A regular pattern of alternating positive and negative stripes along the southern slopes of the Santa Ynez mountains indicates that the 3 arc-second data is not capturing the texture of the canyons evident in the 7.5' data. Statistical analysis indicates a clear relationship between magnitude of slope and magnitude of error.
This particular difference map was created to assist the researchers in exploratory data analysis only. None of the elevation values from the study area were used to develop the parameters for the error model.
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Page created by Ashton Shortridge
Last modified on April 10, 1996
