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SRTM vs NED

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#1
Hans van der Maarel

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Working on a little hobby project at the moment, I was wondering what the major differences from a user's point of view are between 1 arcsecond SRTM and the USGS National Elevation Dataset. Obviously the resolution, but what about the data quality? (Can't get my hands on NED at the moment, seamless.usgs.gov is down for maintenance).
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#2
Hans van der Maarel

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Working on a little hobby project at the moment, I was wondering what the major differences from a user's point of view are between 1 arcsecond SRTM and the USGS National Elevation Dataset. Obviously the resolution, but what about the data quality? (Can't get my hands on NED at the moment, seamless.usgs.gov is down for maintenance).


Answering my own question...

Finally found some 10-m data, assuming it's NED or NED-derived of the area of interest and for now it seems to be better. SRTM has some gaps here and there and filling them always leaves some visible artifacts. NED doesn't seem to have this.
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#3
ProMapper

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You are right about SRTM, it has gaps and any automated patching results in botched surface. I believe NASA had used some other data to fill up the holes and corrected version was available for a price. However some say that SRTM data is true representation of the surface as the radar signal penetrates the canopy of trees and gets reflected from hard surfaces only whereas the visible band from tree tops. Any experts of radiometry or the science of radar?

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#4
Hans van der Maarel

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You are right about SRTM, it has gaps and any automated patching results in botched surface. I believe NASA had used some other data to fill up the holes and corrected version was available for a price. However some say that SRTM data is true representation of the surface as the radar signal penetrates the canopy of trees and gets reflected from hard surfaces only whereas the visible band from tree tops. Any experts of radiometry or the science of radar?


If I'm not mistaken, SRTM has a vertical error of about 16 meters so true or not, with that kind of error it doesn't really matter :)
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#5
Wes Peck

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You are right about SRTM, it has gaps and any automated patching results in botched surface. I believe NASA had used some other data to fill up the holes and corrected version was available for a price. However some say that SRTM data is true representation of the surface as the radar signal penetrates the canopy of trees and gets reflected from hard surfaces only whereas the visible band from tree tops. Any experts of radiometry or the science of radar?


If I'm not mistaken, SRTM has a vertical error of about 16 meters so true or not, with that kind of error it doesn't really matter :)



Depending on the location, the reported vertical error of the NED can be as high as the SRTM. It is important to consider relative error (grid to grid) for the area you are working in. A few years ago I did some comparative anaysis with NED and Lidar. There were some expected differences but overall the data agreed better than I had hoped.




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