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what are YOU getting for Kanchanjunga??? #13

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TFehlh opened this issue Feb 6, 2021 · 1 comment
Open

what are YOU getting for Kanchanjunga??? #13

TFehlh opened this issue Feb 6, 2021 · 1 comment

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@TFehlh
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TFehlh commented Feb 6, 2021

Is anyone able to get the published results for the sample test point: Kanchanjunga, lat: 27.7025, lon: 88.146667?

I've run the author's code, nicholas-fong's code, my code, and the gdallocationifo. None of them come up with the 'correct' elevation.

I think it's a problem with the hgt file I'm using, but can someone else confirm? What are YOU getting?

I downloaded the hgt file from https://dds.cr.usgs.gov/srtm/version2_1/SRTM3. Is there another source? I tried the version1 data with the same result.

Here's the gdallocationinfo that shows the same answer that I am getting.

gdallocationinfo N27E086.hgt -wgs84 86.925278 27.988056
Report:
Location: (1110P,14L)
Band 1:
Value: -32768

@nicholas-fong
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nicholas-fong commented Feb 11, 2021

https://dds.cr.usgs.gov/srtm/version2_1/SRTM3 is permanently shut down. I email USGS yesterday and they confirmed that link is no longer supported.

GeoTIFF is fully supported by USGS delivery site. The user interface at the new delivery site takes a LOT of learning but it works. I posted a small Python code to read elevation from USGS SRTM GeoTIFF https://github.com/nicholas-fong/SRTM-GeoTIFF

gdallocationinfo n27_e086_3arc_v2.tif -wgs84 86.925278 27.988056 (Everest 珠穆朗玛峰, 8765 m peak OpenStreetMap)
Report:
Location: (1110P,14L)
Band 1:
Value: -32767 (v2 of the USGS GeoTIFF still has voids)

gdallocationinfo n27_e088_3arc_v2.tif -wgs84 88.146667 27.7025 (Nepal Kangchenjunga 8586 m peak OpenStreetMap)
Report:
Location: (176P,357L)
Band 1:
Value: -32767 (v2 of the USGS GeoTIFF still as voids)

Download from USGS EarthExplorer (1 Arc-Second) of the GeoTIFF, things look a little bit better:

gdallocationinfo n27_e086_1arc_v3.tif -wgs84 86.925278 27.988056 (Everest 珠穆朗玛峰, 8765 m peak OpenStreetMap)
Report:
Location: (3331P,43L)
Band 1:
Value: 8803

Not a bad result: https://oceanservice.noaa.gov/facts/highestpoint.html#:~:text=Mount%20Everest%2C%20located%20in%20Nepal,from%20which%20elevations%20are%20measured.
says summit of Everest is 8848 meters

gdallocationinfo n27_e088_1arc_v3.tif -wgs84 88.146667 27.7025
Report:
Location: (528P,1071L)
Band 1:
Value: -32767 <---- still has void

Last attempt:
OpenTopography.org, download a GeoTIFF:
(presumably this has more processing to reduce voids)
https://portal.opentopography.org/raster?opentopoID=OTSRTM.042013.4326.1
Data Selection Coordinates:
Xmin: 87.9995833
Xmax: 89.0004167
Ymin: 26.9995833
Ymax: 28.0004167

gdallocationinfo n27_e088.tif -wgs84 88.146667 27.7025 (Nepal Kangchenjunga 8586 m peak OpenStreetMap)
Report:
Location: (176P,357L)
Band 1:
Value: 8291

[n27_e088.zip]
(https://github.com/aatishnn/srtm-python/files/5973394/n27_e088.zip)

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