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Content & Tools => Tools => Topic started by: chbla on March 22, 2016, 20:32:07

Title: Higher resolution elevation data
Post by: chbla on March 22, 2016, 20:32:07
Hi there,

I've got a question, there is quite high-resolution elevation data available for Austria, and I managed to get it loaded in GlobalMapper (see screenshot for a difference between existing hgt files I have vs the high-resolution ones).

As I have no experience with GIS whatsoever I wanted to ask:

1. Are there benefits to using these in Locus, or does it have its own limitation regarding resolution? (e.g. for the slope shading)
2. Can anyone tell me how this should be exported to be usable? I can apparently export it in SRTM 1" and 3" .hgt files which makes me wonder if this reduces that resolution or if it keeps it?

Maybe someone familiar with all this GIS magic can help me.

Thanks a lot,
Christoph
Title: Re: Higher resolution elevation data
Post by: gynta on March 22, 2016, 22:46:26
3"
http://www.viewfinderpanoramas.org/Coverage%20map%20viewfinderpanoramas_org3.htm

1"
http://www.viewfinderpanoramas.org/Coverage%20map%20viewfinderpanoramas_org1.htm
select area of map shading and download it
extract and copy the altitude *:hgt files to Locus/data/srtm directory

make it sense?

3": 1,75MB
1": 24,7MB - whole Alps 2,5 GB (roughly)

Compare...

...slope: http://www.oldboys.at/comp1/
plausible view?

...hillshading: http://www.oldboys.at/comp2/
Title: Re: Higher resolution elevation data
Post by: chbla on March 22, 2016, 22:51:56
Thanks a lot for your answer - but I think you misunderstood. Why download?
The files I want to use are of higher resolution.
Title: Re: Higher resolution elevation data
Post by: gynta on March 22, 2016, 22:55:18
just do it
Title: Re: Higher resolution elevation data
Post by: chbla on March 22, 2016, 22:56:25
Do what? Did you even read my question?
Title: Re: Higher resolution elevation data
Post by: gynta on March 22, 2016, 23:07:17
there is quite high-resolution elevation data available for Austria
http://www.viewfinderpanoramas.org/Coverage%20map%20viewfinderpanoramas_org1.htm
or other source?

Quote
Are there benefits to using these in Locus?
try it

Quote
I can apparently export it in SRTM 1" and 3" .hgt files
great ! - so, just use it.
Title: Re: Higher resolution elevation data
Post by: chbla on March 22, 2016, 23:09:11
it's a different source, a 10m grid (just see my attached image in the first post - it's a comparison between my sources and the ones you posted)

my question is:
2. I can apparently export it in SRTM 1" and 3" .hgt files which makes me wonder if this reduces that resolution or if it keeps it?

Could you give me a link to the area you posted?
I'd like to compare it but cannot find a name on it
Title: Re: Higher resolution elevation data
Post by: gynta on March 22, 2016, 23:17:01
i fear your export ends in the same result.
link to this area? uff  - have to search...
brb
Title: Re: Higher resolution elevation data
Post by: chbla on March 22, 2016, 23:19:10
yes that's what I wan to find out, how to export and use the higher resolution files..
Title: Re: Higher resolution elevation data
Post by: gynta on March 22, 2016, 23:24:19

(http://s11.postimg.org/7dz1bjybz/2016_03_22_232303.png) (http://postimage.org/)
Title: Re: Higher resolution elevation data
Post by: chbla on March 22, 2016, 23:29:01
Ah I did not generate the data for this point yet - if you have elevation data for all parts of Austria, could you maybe take a screenshot of 47.3573592,9.7254071 with the zoom/scale set to 400m and slope shading on? I'd like to compare it as I have two different files
Title: Re: Higher resolution elevation data
Post by: gynta on March 22, 2016, 23:30:49
sure...
1" and 3" ?
Title: Re: Higher resolution elevation data
Post by: chbla on March 22, 2016, 23:31:11
if possible yes, but 1" would be enough I think
Title: Re: Higher resolution elevation data
Post by: gynta on March 22, 2016, 23:46:02
(http://s12.postimg.org/qu32m1rmx/2016_03_22_234042.jpg) (http://postimg.org/image/qu32m1rmx/)

(http://s12.postimg.org/ueyy59w6h/2016_03_22_233815.jpg) (http://postimg.org/image/ueyy59w6h/) . (http://s12.postimg.org/cmddxeey1/2016_03_22_234439.jpg) (http://postimg.org/image/cmddxeey1/) 1"

(http://s12.postimg.org/u4w0zo6y1/2016_03_22_234007.jpg) (http://postimg.org/image/u4w0zo6y1/) . (http://s12.postimg.org/i1m3yd6i1/2016_03_22_234250.jpg) (http://postimg.org/image/i1m3yd6i1/) 1"

...blurry because it was 143% of zoom16
Title: Re: Higher resolution elevation data
Post by: chbla on March 23, 2016, 00:05:33
Looks really different ..
which map/style did you use exactly so I can compare better?
Title: Re: Higher resolution elevation data
Post by: gynta on March 23, 2016, 00:07:29
last LoMap of austria from store
and http://forum.locusmap.eu/index.php?topic=4982.msg41086#msg41086  HiLo theme
Title: Re: Higher resolution elevation data
Post by: chbla on March 23, 2016, 00:11:44
Ah, I don't have that one.
However, I've attached a screenshot with hike&bike osm classic

(http://s17.postimg.org/n39zvi8q3/image.jpg) (http://postimg.org/image/n39zvi8q3/)  (http://s17.postimg.org/9xuhpeeuj/image.jpg) (http://postimg.org/image/9xuhpeeuj/)
Title: Re: Higher resolution elevation data
Post by: chbla on March 23, 2016, 00:17:03
Here is a better comparison, in GlobalMapper you can actually see the difference in detail:

SRTM 1" from Viewfinder (the one that you have)
https://dl.dropboxusercontent.com/u/311345/gps/viewfinder_srtm1.png

SRTM 1" my Version, better resolution
https://dl.dropboxusercontent.com/u/311345/gps/my_srtm1.png
Title: Re: Higher resolution elevation data
Post by: gynta on March 23, 2016, 00:51:44
Nice and clear in GlobalMapper but what's nearly realistic inside Locus?
Title: Re: Higher resolution elevation data
Post by: chbla on March 23, 2016, 00:54:21
Yes, the files I have are much better than the SRTM1 ones.
But check this one, this is the original:
https://dl.dropboxusercontent.com/u/311345/gps/high_detail.png
That's why my initial question was how to export it for maximum resolution.

Best to compare all 3:
SRTM1 https://dl.dropboxusercontent.com/u/311345/gps/viewfinder_srtm1.png
SRTM1my https://dl.dropboxusercontent.com/u/311345/gps/my_srtm1.png
Orig https://dl.dropboxusercontent.com/u/311345/gps/high_detail.png

As you say I don't know where the limits of locus are, that's why I'm asking - but I assume better quality does not harm.
Title: Re: Higher resolution elevation data
Post by: poutnikl on March 23, 2016, 06:58:09
it's a different source, a 10m grid (just see my attached image in the first post - it's a comparison between my sources and the ones you posted)

my question is:
2. I can apparently export it in SRTM 1" and 3" .hgt files which makes me wonder if this reduces that resolution or if it keeps it?

That is strange, as 1" and 3" are 30 and 90m grid, respectively.  ( 1' is 1 nautical mile 1852 m, 1800/60  = 30 )

The known problem with SRTM artefacts remain ( woods, narrow valleys, urban canyons, rivers, bridges)
 as reportedly tested by Brouter author, they have just better details.
Title: Re: Higher resolution elevation data
Post by: chbla on March 23, 2016, 08:17:47
@poutnikl, see the files above, I'm just comparing SRTM 1" with my data that I exported as "SRTM 1" in global mapper as this exports to .hgt.

The underlying data is not 30/90 resolution but 10m (I also have 5m).
Title: Re: Higher resolution elevation data
Post by: poutnikl on March 23, 2016, 09:42:03
I see. It is known that not all elevation data are SRTM based, therefore thanks for explanation.
Title: Re: Higher resolution elevation data
Post by: chbla on March 23, 2016, 13:39:20
What digital elevation data files/formats can locus handle exactly?
Title: Re: Higher resolution elevation data
Post by: chbla on March 24, 2016, 18:57:34
I noticed that the SRTM .hgt format itself limits a higher resolution :/