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December 26, 2024

Discrepancy between USGS topo map and DEM data? – January 29, 2023 at 08:31PM

I’m trying to calculate the “low laying” acreage within a vineyard that is more prone to frost damage. I did so using 1/3 arc-second DEM data from USGS to make a zonal map with stretched symbology. However, when I compare this to the US Topo map, there seems to be a big discrepancy in units and/or values? The highest elevation in my DEM data is 75m however the topo map shows upwards of 200m. The trends of the contour lines match well but the values are quite different.

Any idea why this could be? I didn’t transform the data after downloading from USGS – just clipped the raster to my vineyard boundary. Any info is much appreciated!

submitted by /u/cheeseartist3309C
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