Terrain

[John60]

Hi

Just feeding back - not complaining - programme is fantastic

Downloaded all there is of Shetland Isles, UK - twice - just to be sure it wasn't damaged cache etc

The terrain data is seriously messed up - part of the islands are excellent - but the northern half is either flat - has massive cliffs - which are not there honest - or have huge leaps in height data. I can post some shots if you would find it useful

Seems like there are 3 intersecting areas of terrain data - which do not match up and leave the whole thing in a mess - is this just a damaged server store - or is there no proper data at all

Like I said - just feedback so the data can be checked - and deleted from the proxy if it's bad and fixable

Cheers

John

[Thomas Risan]

Originally posted by John60@Dec 12 2004, 12:45 AM
Hi

Just feeding back - not complaining - programme is fantastic

Downloaded all there is of Shetland Isles, UK - twice - just to be sure it wasn't damaged cache etc

The terrain data is seriously messed up - part of the islands are excellent - but the northern half is either flat - has massive cliffs - which are not there honest - or have huge leaps in height data.ÂÂ* I can post some shots if you would find it useful

Seems like there are 3 intersecting areas of terrain data - which do not match up and leave the whole thing in a mess - is this just a damaged server store - or is there no proper data at all

Like I saidÂÂ* - just feedback so the data can be checked - and deleted from the proxy if it's bad and fixable

Cheers

John
Quoted post


Hi John,
the reason for your odd elevation data is the location of the Faeroe Islands. They are above 60 degrees north, which is the extent of the terrain model made by the space shuttle elevation data. We unfortunate ones interested in elevation data further north than this will have to find some free data source and provide these data to the WW people :)

[Guest]

Originally posted by Thomas Risan@Dec 11 2004, 03:50 PM
Hi John,
the reason for your odd elevation data is the location of the Faeroe Islands. They are above 60 degrees north, which is the extent of the terrain model made by the space shuttle elevation data. We unfortunate ones interested in elevation data further north than this will have to find some free data source and provide these data to the WW people :)
Quoted post


Well I can't actually get anything for the Faeroe Islands at all - never mind terrain - no pictures, zilch - it's just a big black hole - but Shetland is at 60 degrees - and like I said half of it is perfect - but the rest isn't.

May just be because of the lack of any data further north that is messing it up - but Iceland has full terrain - I think :unsure:

[Thomas Risan]

Sorry, my mistake. I meant the Shetlands. But it has to do with the space shuttle trajectory, since the elevation data have been made fro data collected with the space shuttle. if you have the lat/long grid on and find the 60-61 degree area in Norway you will find the same phenomena.

[Guest]

Originally posted by Thomas Risan@Dec 11 2004, 04:01 PM
Sorry, my mistake. I meant the Shetlands. But it has to do with the space shuttle trajectory, since the elevation data have been made fro data collected with the space shuttle. if you have the lat/long grid on and find the 60-61 degree area in Norway you will find the same phenomena.
Quoted post


Ah yes - had a look - I see your point - obviously this is the bare periphery of the data collection and it's just incorrect - probably at it's feedback limit. Have to go and find a DEM to feed in now

Thanks for the quick feedback

Cheers

John

[Andrew]

This program is fantastic! it's great for school. just one thing though. For most of south australia the texture and the 3d terrain do not match. in some places it's not so bad only a couple houndred meters, other places it's a thousand. is this download error

[TomServo]

Originally posted by Andrew@Dec 16 2004, 02:10 AM
This program is fantastic! it's great for school. just one thing though. For most of south australia the texture and the 3d terrain do not match. in some places it's not so bad only a couple houndred meters, other places it's a thousand. is this download error
Quoted post


Yes, that is a well known issue. It deals witht he landsat mosaics and the WW curving of the images to fit the globe.

It is being worked on and fixed.

[Lucian]

The SRTM instrument is not perfect either. It is side looking, and if there is a steep
mountain that blocks the view, you get no data (gap) for areas in the "shade".
The other issues are "flat" areas. Since SRTM needs some sort of discernable
height detail to resolve the elevation, flat areas do not resolve, producing a another
kind of gaps. If you look at the SRTM browser via USGS (seamless.usgs.gov), you
will notice the gaps. The "shadow" gaps are somewhat masked in that viewer but
the "flat" gaps are there.
Chris ran a "SRTM patch" code that tries to hide these gaps by interpolation. Of
course, it does not match the real elevation.

Lucian

Originally posted by Thomas Risan@Dec 11 2004, 04:50 PM
Hi John,
the reason for your odd elevation data is the location of the Faeroe Islands. They are above 60 degrees north, which is the extent of the terrain model made by the space shuttle elevation data. We unfortunate ones interested in elevation data further north than this will have to find some free data source and provide these data to the WW people :)
Quoted post