[Q] How to get the right information about altitude

[gynta]

Test with high resolution hgt file:
http://forum.locusmap.eu/index.php?topic=2936.msg19528#msg19528

[szebenyib]

Hmmm interesting news and nice work! Can you please tell me how big the difference is between the new and the old version in say 10, 50 kms?

[Christian]

Test with high resolution hgt file:
http://forum.locusmap.eu/index.php?topic=2936.msg19528#msg19528

You are always one step ahead

[gynta]

small tutorial how to get SRTM1 data as .hgt files working in Locus

and what's wrong with...

Direct links to SRTM1 look like this...

?

[Christian]

Second impression of SRTM 1:
: SRTM1 data don't solve my problem with small canyon I get 7m uphill instead of 5m before, but it should be at least 16m
: Guess, hillshading with SRTM1 data needs more power than with SRTM3 especially when zooming in / out many times. Menion & Petr, did you test it and can you confirm more power?


Thanx Gynta for sniffing indexes Looks like updated data after Sept / 2014.

[voldapet]

It's more on menion...anyway SRTM1 hgt file contains 9 times more data then SRTM3 file.For this reason hill shading with SRTM1 files is more time and power consuming.

[Menion]

If there will be interest, I may spend some time and measure it more precisely, but there should be no reason for higher CPU and memory requirements, no matter how big HGT files are.

[Christian]

No, thanx for offering. Its not worth to spend some time on it. Having 9 times more data it must be 9 times more computation...
I noticed a little delay when zooming in /out. So I wanted to ask for experience only.

[Menion]

amount of data should make no difference as I wrote. Locus divide every tile (256x256 px) on a small grid and compute altitude values from HGT file for every single point in this small grid.

But this value is computed just from four nearest altitude values from file. And obtain of these four values is independent on file size as Locus directly skip to exact place where required value is in file (I'm now anyway not 100% sure that size of file has no influence, but should not).

[tommi]

amount of data should make no difference as I wrote. Locus divide every tile (256x256 px) on a small grid and compute altitude values from HGT file for every single point in this small grid.

But this value is computed just from four nearest altitude values from file. And obtain of these four values is independent on file size as Locus directly skip to exact place where required value is in file (I'm now anyway not 100% sure that size of file has no influence, but should not).

Menion, I can't understand your description completely but does it really describe the algorithm for hill-shading?

[Menion]

yes . Nevermind ...