SRTM3 MakeAHMap discrepancies

[JimmyD3]

Pulling map data from srtm3 seems to always come up with some strange elevation anomalies, but they are not present when using srtm30 or gtopo30. See attached elevation graphics.

[captain1ma]

fixed!! mine works perfectly!

[JimmyD3]

Okay Jaeger, here's the magic word "Please" tell me how to fix it. 

[captain1ma]

LOL it was ugly!! we had to rename all the files in the download_source.txt file and that allowed it to work. easyscor link got you too the page, but then you had to rename ALL the files. if you would like me to email you the file just PM me your email address and ill get it to you

[Easyscor]

fixed!! mine works perfectly!

SEE why I tell you to check it in the Terrain Editor! I did warn you.

The source site either changed the srtm's or the compression method changed, or both.

Kenai is exactly right, a corrugated terrain anomaly is baked into the terrain now.

I guess I need to allow that something might have went amiss with the makemap program, but that would be very surprising.

[Easyscor]

Googling "SRTMGL1 format" returns a page of links explaining some of the changes. The hgt extension stands for height. It has replaced the old digital elevation, dem extension.

[captain1ma]

easyscor is a meanie!! ok so i jumped the gun!

[artik]

Googling "SRTMGL1 format" returns a page of links explaining some of the changes. The hgt extension stands for height. It has replaced the old digital elevation, dem extension.

Updated file links contain exactly the same files i got exactly the same file bit by bit as before update

[JimmyD3]

The SRTM3 data generates corrugated maps. Not sure why, SRTM30 or gotop30 work fine.

[captain1ma]

i build most of my terrains with srtm30. if that still works i might be good then!

[artik]

The SRTM3 data generates corrugated maps. Not sure why, SRTM30 or gotop30 work fine.

STRM3 is known to have inaccuracies - it is quite raw data while SRTM30 has lower resolution but filtered.

I assume it happens only in some ares? If you have troubles switch to 30. I'll see what I can do.

[JimmyD3]

STRM3 is known to have inaccuracies - it is quite raw data while SRTM30 has lower resolution but filtered.

I assume it happens only in some ares? If you have troubles switch to 30. I'll see what I can do.

Okay, thanks for the update, so far I have been using SRTM30 and GOTOP30 they both work reliably.
That default elevation option would really open up other areas for use in maps as well. Again thanks for all your hard work, it makes a dramatic difference in map development and real life landscapes, especially for an old country boy like me. 

[Easyscor]

Artik I'm seeing the same corrugations in the default 512 BoB output. It's even mirrored in the CBM that the Terrain Editor builds:

[Easyscor]

This has all the signs that the data has been deliberately obfuscated. The original CIA river data files had the same type of issue. This happens when the “stake holders” protect their, paid for by the USA taxpayer, work.

[artik]

Clearly your data is corrupted.

My freshly downloaded BoB looks ok.

Can you please:

1. cleanup/move/backup content of data/srtm3 folder - such that it is empty of any previously downloaded files.
2. update your download sources from there with fixed urls: https://raw.githubusercontent.com/artyom-beilis/makeahmap/master/download_sources.txt
3. Rerun makeahmap on BoB area so it would download fresh srtm3 data.


Note, if same thing happens... try to repeat the steps with anti-virus disabled.