Board index FlightGear Development Scenery

SRTM 1-arcsecond global

Questions and discussion about enhancing and populating the FlightGear world.

SRTM 1-arcsecond global

Postby lomar » Sun Jun 30, 2019 1:14 am

https://www.usgs.gov/centers/eros/science/usgs-eros-archive-digital-elevation-shuttle-radar-topography-mission-srtm-1-arc?qt-science_center_objects=0#qt-science_center_objects

so It seems that recently(at least it's more recent than the WS2.0 release) USGS has released a global SRTM dataset with 1-arcsecond resolution(previous data was 1-arcsecond for USA only and 3-arcsecond for the rest of the world apparently)

so, is it of any relevance for us? can this new elevation data be used for building scenery for FG or would there be any issues(like licensing or bugs)
lomar
 
Posts: 219
Joined: Mon Jun 30, 2014 1:38 am
Location: Rio de Janeiro, Brazil
Callsign: lomar
Version: latest
OS: win 10

Re: SRTM 1-arcsecond global

Postby frtps » Sun Jun 30, 2019 3:05 am

I tried out this for the Sydney (Australia) area and was disappointed that the central business district was very "peaky" presumably due to the tall buildings. I've gone back to SRTM-3 as it somewhat smooths out the topography in these areas. I've always wondered how this is dealt with in other city centres built using SRTM-1.
frtps
 
Posts: 49
Joined: Sun Aug 05, 2018 9:58 am

Re: SRTM 1-arcsecond global

Postby wlbragg » Sun Jun 30, 2019 3:34 am

Wow, that's great. But really the difference between the 1 VS 3 isn't that much and If there is no editing of man made structures spikes then it may not work well That is why the "Panoramic" site data is used for the global scenery build, because they have cleaned up a lot of those issues.
I suppose if someone was really motivated to learn how to clean this data up, it would be cool to be able to use 1arc-sec for the entire world.
Kansas(2-27-15)/Ohio/Midwest scenery development.
KEQA (2-27-15), 3AU, KRCP Airport Layout
Intel i5 3570K AMDRX480
User avatar
wlbragg
 
Posts: 4989
Joined: Sat Aug 25, 2012 11:31 pm
Location: Kansas (Tornado Alley), USA
Callsign: WC2020
Version: next
OS: Win10/Linux/AMDRX480

Re: SRTM 1-arcsecond global

Postby xDraconian » Sun Jun 30, 2019 3:47 am

SRTMGL1 has been used for the Hawaiian Islands and Tennessee - not sure what has been used for Iceland, but likely SRTM-3.

I consider SRTMGL1 the preferred data source as there are no void areas. The void areas having been supplied from other non-proprietary data sources.
1-arc-second or better resolution requires careful decimation to reduce the vertices count to something reasonable. We do the same for 3-arc-second data sources, but it's even more important with the higher-resolution sources.

The issue with "peaky" terrain, most often found in urban areas, is often due to Digital Surface Model (DSM) data being utilized to fill the voids. A DSM represents the surface (including man-made objects - e.g. buildings). These areas can be flattened in GIS software.
xDraconian
 
Posts: 240
Joined: Sun Jan 21, 2018 5:53 am
Version: Git
OS: Linux Mint

Re: SRTM 1-arcsecond global

Postby legoboyvdlp » Sun Jun 30, 2019 8:36 am

Viewfinder panorama is far far superior for our purposes (unless you have the skills to edit the data!) since it has been cleaned. The main advantage of SRTM-1 is when mountains etc are where it helps to have a hi-res data source.

Are those proprietary data sources compatible with GPL? Is the finished product still public domain?

It seems that terrafit has trouble with SRTM-3 on the next branch as it makes large 40000 foot spikes etc :? So using SRTM-1 or an older version would seem to be required at least on my PC. I will try and investigate the issues...
User avatar
legoboyvdlp
 
Posts: 7164
Joined: Sat Jul 26, 2014 1:28 am
Callsign: YV-LEGO
Version: 2018.3.1
OS: Windows 10 HP

Re: SRTM 1-arcsecond global

Postby vnts » Tue Jul 02, 2019 7:37 am

legoboyvdlp wrote in Sun Jun 30, 2019 8:36 am:Viewfinder panorama is far far superior for our purposes (unless you have the skills to edit the data!) since it has been cleaned.


Would taking clean urban areas from SRTM-3 (giving them priority to override SRTMGL1 data) and the rest from SRTMGL1 be a shortcut that avoids cleaning? ..or is that also difficult

Kind regards
vnts
 
Posts: 101
Joined: Thu Apr 02, 2015 12:29 am

Re: SRTM 1-arcsecond global

Postby legoboyvdlp » Tue Jul 02, 2019 1:31 pm

I'm not so sure if the toolchain supports that, if it does it certainly would make sense to do that.
User avatar
legoboyvdlp
 
Posts: 7164
Joined: Sat Jul 26, 2014 1:28 am
Callsign: YV-LEGO
Version: 2018.3.1
OS: Windows 10 HP

Re: SRTM 1-arcsecond global

Postby xDraconian » Tue Jul 02, 2019 4:15 pm

The toolchain does not support merging of different formats. A potential solution would be to pass a 'flattening of abrupt elevation changes' parameter for urban/town areas. A more flexible solution would be to also support a flattening shapefile defining a mask to be used to limit where the flattening was allowed.
xDraconian
 
Posts: 240
Joined: Sun Jan 21, 2018 5:53 am
Version: Git
OS: Linux Mint


Return to Scenery

Who is online

Users browsing this forum: No registered users and 2 guests