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coordinate system in terrain

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vijeesh
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Joined: 25 Dec 2010
Posts: 36

PostPosted: Tue Feb 22, 2011 5:29 am    Post subject:
coordinate system in terrain
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Dear All,

What will be the projection type If I specify --geocentric option to osgdem. ie whether it'll be UTM/ECEF/Flat/ECI.
The command I used is osgdem --geocentric -t 77-12_geo_wgs84.tif -d N12E77.hgt -l 4 -o terrain.ive

Gdal info of source files are given below

Driver: GTiff/GeoTIFF
Files: 77-12_geo_wgs84.tif
Size is 5961, 6073
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]]
Origin = (76.992187500000000,13.025965925032700)
Pixel Size = (0.000169547491327,-0.000169547491327)

Driver: SRTMHGT/SRTMHGT File Format
Files: N12E077.hgt
Size is 1201, 1201
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
TOWGS84[0,0,0,0,0,0,0],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9108"]],
AUTHORITY["EPSG","4326"]]
Origin = (76.999583333333334,13.000416666666666)
Pixel Size = (0.000833333333333,-0.000833333333333)

Thank you!

Cheers,
Vijeesh
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J.P. Delport
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PostPosted: Tue Feb 22, 2011 7:03 am    Post subject:
coordinate system in terrain
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WGS84 ECEF AFAIK, check with osgpick.

jp

On 22/02/11 07:29, Vijeesh Theningaledathil wrote:
Quote:
Dear All,

What will be the projection type If I specify --geocentric option to osgdem. ie whether it'll be UTM/ECEF/Flat/ECI.
The command I used is osgdem --geocentric -t 77-12_geo_wgs84.tif -d N12E77.hgt -l 4 -o terrain.ive

Gdal info of source files are given below

Driver: GTiff/GeoTIFF
Files: 77-12_geo_wgs84.tif
Size is 5961, 6073
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433],
AUTHORITY["EPSG","4326"]]
Origin = (76.992187500000000,13.025965925032700)
Pixel Size = (0.000169547491327,-0.000169547491327)

Driver: SRTMHGT/SRTMHGT File Format
Files: N12E077.hgt
Size is 1201, 1201
Coordinate System is:
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84",6378137,298.257223563,
AUTHORITY["EPSG","7030"]],
TOWGS84[0,0,0,0,0,0,0],
AUTHORITY["EPSG","6326"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9108"]],
AUTHORITY["EPSG","4326"]]
Origin = (76.999583333333334,13.000416666666666)
Pixel Size = (0.000833333333333,-0.000833333333333)

Thank you!

Cheers,
Vijeesh

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vijeesh
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Joined: 25 Dec 2010
Posts: 36

PostPosted: Tue Feb 22, 2011 9:55 am    Post subject:
coordinate system in terrain
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Hi,
Thanks. But can you please tell me how to check using osgpick.


Thank you!

Cheers,
Vijeesh
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J.P. Delport
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PostPosted: Tue Feb 22, 2011 10:47 am    Post subject:
coordinate system in terrain
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Hi,

generate your terrain and then run:
osgpick myterrain.ive

then click on the terrain. The values you get would should you the
coordinates of the geometry.

jp

On 22/02/11 11:55, Vijeesh Theningaledathil wrote:
Quote:
Hi,
Thanks. But can you please tell me how to check using osgpick.


Thank you!

Cheers,
Vijeesh

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http://forum.openscenegraph.org/viewtopic.php?p=36929#36929







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vijeesh
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Joined: 25 Dec 2010
Posts: 36

PostPosted: Tue Feb 22, 2011 12:07 pm    Post subject:
coordinate system in terrain
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Hi,
Thanks. But how can I make out whether it's UTM or FLAT earth or ECEF?


Thank you!

Cheers,
Vijeesh
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Glenn Waldron
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PostPosted: Tue Feb 22, 2011 1:19 pm    Post subject:
coordinate system in terrain
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Vijeesh,

JP is correct; it will be ECEF on a WGS84 ellipsoid.


Glenn Waldron : Pelican Mapping : osgEarth


On Tue, Feb 22, 2011 at 7:07 AM, Vijeesh Theningaledathil < (
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Quote:
Hi,
Thanks. But how can I make out whether it's UTM or FLAT earth or ECEF?


Thank you!

Cheers,
Vijeesh

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J.P. Delport
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PostPosted: Tue Feb 22, 2011 1:23 pm    Post subject:
coordinate system in terrain
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For ECEF the vector length should be close to the earth radius. For flat
you'll get heights that make sense ito altitude and probably x/y in
degrees. Not sure about difference with UTM.

Experiment a bit.

jp

On 22/02/11 14:07, Vijeesh Theningaledathil wrote:
Quote:
Hi,
Thanks. But how can I make out whether it's UTM or FLAT earth or ECEF?


Thank you!

Cheers,
Vijeesh

------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=36942#36942







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S2LR
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Joined: 13 Nov 2010
Posts: 208

PostPosted: Tue Feb 22, 2011 5:38 pm    Post subject:
coordinate system in terrain
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If you're specifying --geocentric, it will definitely not be UTM. This
is a flat earth coordinate system. Geocentric coordinate systems are
round earth oblate spheroid (i.e. geodetic lat lon maps to (x,y,z)
Cartesian coordinates with (0,0,0) being the center of the earth)...

-Shayne

-----Original Message-----
From:
[mailto:] On Behalf Of Vijeesh
Theningaledathil
Sent: Tuesday, February 22, 2011 5:07 AM
To:
Subject: Re: [vpb] coordinate system in terrain

Hi,
Thanks. But how can I make out whether it's UTM or FLAT earth or ECEF?


Thank you!

Cheers,
Vijeesh

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vijeesh
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Joined: 25 Dec 2010
Posts: 36

PostPosted: Wed Feb 23, 2011 8:35 am    Post subject:
Reply with quote

Hi,

Thanks JP. By vector length you mean Local vertex or World vertex. If I created the terrain using geocentric option I'm getting local vertex with x/y and alt in meters and world vertex in some 7 digit number. But when the terrain is created without geocentric option the world coordinate vertex is showing lat/lon in degrees and altitude in some units (may be degree). And Shayne is telling it is flat earth terrain. So which one I should select.


Thank you!

Cheers,
Vijeesh
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J.P. Delport
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PostPosted: Wed Feb 23, 2011 1:18 pm    Post subject:
coordinate system in terrain
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Hi,

On 23/02/11 10:35, Vijeesh Theningaledathil wrote:
Quote:
Hi,

Thanks JP. By vector length you mean Local vertex or World vertex.
If I created the terrain using geocentric option I'm getting local
vertex with x/y and alt in meters and world vertex in some 7 digit
number. But when the terrain is created without geocentric option the
world coordinate vertex is showing lat/lon in degrees and altitude in
some units (may be degree). And Shayne is telling it is flat earth
terrain. So which one I should select.

Depends on what you want to do... For whole earth type viewing I'd
always go with geocentric. Flat might be an option if you want small
area or map type view.

jp

Quote:


Thank you!

Cheers, Vijeesh

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vijeesh
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Joined: 25 Dec 2010
Posts: 36

PostPosted: Wed Feb 23, 2011 3:34 pm    Post subject:
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Hi,

How can I generate terrain in UTM coordinate using osgdm?. Also I'm still confused about terrain type(flat/ecef identification) from vertex information. ie. local vertex/world vertex?. (if local vertex is x,y alt which terrain its?or if global vertex is in lat lon alt in deg which type is) Can you please clarify on that.
Thank you!

Cheers,
Vijeesh
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S2LR
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Joined: 13 Nov 2010
Posts: 208

PostPosted: Wed Feb 23, 2011 3:55 pm    Post subject:
coordinate system in terrain
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If the source data is using UTM coordinates already, you can just do

osgdem --TERRAIN --PagedLOD -t texturedir -d elevdir -l 10 -o
utmdatabase.ive

If the source data is not using UTM, you can use gdal to reproject the
data by

gdalwarp -t_srs "proj=utm +zone=11 +datum=WGS84" infile outfile

If gdalwarp complains, try the command

gdalwarp -s_srs "proj=latlong +datum=WGS84" -t_srs "proj=utm +zone=11
+datum=WGS84" infile outfile

In either case, "outfile" is the new source data you'll feed into the
osgdem command above.

I picked "zone 11" as an example for UTM. You'll need to choose your own
zone for your purposes.

-Shayne

-----Original Message-----
From:
[mailto:] On Behalf Of Vijeesh
Theningaledathil
Sent: Wednesday, February 23, 2011 8:35 AM
To:
Subject: Re: [vpb] coordinate system in terrain

Hi,

How can I generate terrain in UTM coordinate using osgdm?

Thank you!

Cheers,
Vijeesh

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http://forum.openscenegraph.org/viewtopic.php?p=37026#37026






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vijeesh
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Posts: 36

PostPosted: Fri Feb 25, 2011 6:56 am    Post subject:
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Hi Shayne
Thanks. But still I cannot make out how to differentiate between flat earth and ECEF. Is there anything we can check to identify?



Thank you!

Cheers,
Vijeesh
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Ralf Stokholm
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PostPosted: Fri Feb 25, 2011 7:16 am    Post subject:
coordinate system in terrain
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Hi Vijeesh

Is it the source data or your generated terrain you wish to id?


If its your source data you can use gdalinfo.exe it will output information on the projection of your source data, your generated terrain will be in the same projection unless you specify something else.


If you generate a ive binary terrain you can use osgconv to convert the root terrain file to .osg you can then inspect this using a text editor. the root file contains a coordinate system node detailing the coordinate system the terrain is using.


brgs


Ralf

On 25 February 2011 07:56, Vijeesh Theningaledathil < (
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)> wrote:
Quote:
Hi Shayne
Thanks. But still I cannot make out how to differentiate between flat earth and ECEF. Is there anything we can check to identify?



Thank you!

Cheers,
Vijeesh

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http://forum.openscenegraph.org/viewtopic.php?p=37117#37117






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vijeesh
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Joined: 25 Dec 2010
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PostPosted: Fri Feb 25, 2011 7:49 am    Post subject:
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Hi,

Thanks Mr. Ralf. But from the output of gdalinfo, how can i say that it is flat earth or round earth. In my first post i had pasted the output of gdalinfo for the source files. My problem is I'm not able to render the terrain generated from the above source files using any of the IG(subrscene, delta3d). Can you tell me which IG is best suitable to render the terrain.
And I need to know the origin lat lon if its a flat earth. I used osgdem to generate my terrain with --geocentric option.


Thank you!

Cheers,
Vijeesh
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