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osgdem and HAE/MSL


 
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nsm4d (Nick Modly)
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Joined: 19 Apr 2013
Posts: 22

PostPosted: Mon Aug 26, 2013 5:45 am    Post subject:
osgdem and HAE/MSL
Reply with quote

Hi,

When providing elevation data to osgdem. is it expected to be in HAE (height above ellipoid), or MSL (mean sea level), or can it tell from the input? For example, I am providing elevation data in the AIG/Arc/Info Binary Grid format (.adf). The data represents the elevation of the area in meters MSL. However, when I osgpick a point and convert it to Lat-Lon-Alt MSL, the altitude is off by about 30m (the difference between HAE and MSL at this location).

This are the options I ran osgdem with
$ osgdem --geocentric -o output.ive -l 8 -d ./path-to-dted/ -t image.tif

Is it possible to specify a vertical datum or coordinate system, such as EGM96?


Thank you!

Cheers,
Nick
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nsm4d (Nick Modly)
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Joined: 19 Apr 2013
Posts: 22

PostPosted: Thu Sep 12, 2013 11:42 am    Post subject:
osgdem and HAE/MSL
Reply with quote

Hi,

When providing elevation data to osgdem. is it expected to be in HAE (height above ellipoid), or MSL (mean sea level), or can it tell from the input? For example, I am providing elevation data in the AIG/Arc/Info Binary Grid format (.adf). The data represents the elevation of the area in meters MSL. However, when I osgpick a point and convert it to Lat-Lon-Alt MSL, the altitude is off by about 30m (the difference between HAE and MSL at this location).

This are the options I ran osgdem with
$ osgdem --geocentric -o output.ive -l 8 -d ./path-to-dted/ -t image.tif

Is it possible to specify a vertical datum or coordinate system, such as EGM96?


Thank you!

Cheers,
Nick

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http://forum.openscenegraph.org/viewtopic.php?p=55984#55984







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S2LR
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Joined: 13 Nov 2010
Posts: 208

PostPosted: Thu Sep 12, 2013 5:37 pm    Post subject:
osgdem and HAE/MSL
Reply with quote

Nick,

Osgdem will work with the input elevation. It will build the database based
on the input source. For example if you're using DTED and the geocentric
option, it will place the point at the specified elevation (in meters) above
the ellipsoid. The point is represented in the Cartesian ECEF geocentric
space (e.g. x,y,z).

The default ellipsoid used is WGS84. You can specify the polar and
equatorial radii in osgdem to fit to another ellipsoid. Just make sure you
specify those radii in your EllipsoidModel class on the rendering side so
that things match up. The EllipsoidModel class also defaults to WGS84...

HTH

-Shayne

-----Original Message-----
From:
[mailto:] On Behalf Of Nick Modly
Sent: Sunday, August 25, 2013 11:46 PM
To:
Subject: [vpb] osgdem and HAE/MSL

Hi,

When providing elevation data to osgdem. is it expected to be in HAE (height
above ellipoid), or MSL (mean sea level), or can it tell from the input? For
example, I am providing elevation data in the AIG/Arc/Info Binary Grid
format (.adf). The data represents the elevation of the area in meters MSL.
However, when I osgpick a point and convert it to Lat-Lon-Alt MSL, the
altitude is off by about 30m (the difference between HAE and MSL at this
location).

This are the options I ran osgdem with
$ osgdem --geocentric -o output.ive -l 8 -d ./path-to-dted/ -t image.tif

Is it possible to specify a vertical datum or coordinate system, such as
EGM96?


Thank you!

Cheers,
Nick

------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=55984#55984









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gwaldron (Glenn Waldron)
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Joined: 25 Aug 2011
Posts: 190

PostPosted: Thu Sep 12, 2013 5:56 pm    Post subject:
osgdem and HAE/MSL
Reply with quote

Nick, Shayne,

I have not looked at VPB in a while, but I believe it expects height values to be referenced to the WGS84 ellipsoid. If that's the case you'll need to convert it first to HAE.


By the way: DTED heights are referenced to the EGM96 geoid (not to the WGS84 ellipsoid). So they need conversion in order to be properly displayed. GDAL (up until recently?) does not convey this information so there's no way for the application to know. You just have to know Smile



Glenn Waldron / @glennwaldron


On Thu, Sep 12, 2013 at 1:45 PM, Tueller, Shayne R Civ USAF AFMC 519 SMXS/MXDEC < (
Only registered users can see emails on this board!
Get registred or enter the forums!
)> wrote:
Quote:
Nick,

Osgdem will work with the input elevation. It will build the database based
on the input source. For example if you're using DTED and the geocentric
option, it will place the point at the specified elevation (in meters) above
the ellipsoid. The point is represented in the Cartesian ECEF geocentric
space (e.g. x,y,z).

The default ellipsoid used is WGS84. You can specify the polar and
equatorial radii  in osgdem to fit to another ellipsoid. Just make sure you
specify those radii in your EllipsoidModel class on the rendering side so
that things match up. The EllipsoidModel class also defaults to WGS84...

HTH

-Shayne

-----Original Message-----
From: (
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[mailto: (
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)] On Behalf Of Nick Modly
Sent: Sunday, August 25, 2013 11:46 PM
To: (
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)
Subject: [vpb] osgdem and HAE/MSL

Hi,

When providing elevation data to osgdem. is it expected to be in HAE (height
above ellipoid), or MSL (mean sea level), or can it tell from the input? For
example, I am providing elevation data in the AIG/Arc/Info Binary Grid
format (.adf). The data represents the elevation of the area in meters MSL.
However, when I osgpick a point and convert it to Lat-Lon-Alt MSL, the
altitude is off by about 30m (the difference between HAE and MSL at this
location).

This are the options I ran osgdem with
$ osgdem --geocentric -o output.ive -l 8 -d ./path-to-dted/ -t image.tif

Is it possible to specify a vertical datum or coordinate system, such as
EGM96?


Thank you!

Cheers,
Nick

------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=55984#55984





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S2LR
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Joined: 13 Nov 2010
Posts: 208

PostPosted: Thu Sep 12, 2013 6:11 pm    Post subject:
osgdem and HAE/MSL
Reply with quote

Glenn,

VPB does reference to the WGS84 for the --geocentric option.

So to do the conversion, do you have to remove the contribution of the geoid
(gravitational equipotential surface) from the raw DTED first before pumping
it into VPB? Is there an application that does this?

Thanks,
-Shayne

-----Original Message-----
From:
[mailto:] On Behalf Of Glenn
Waldron
Sent: Thursday, September 12, 2013 12:04 PM
To: OpenSceneGraph Users
Subject: Re: [vpb] osgdem and HAE/MSL

Nick, Shayne,

I have not looked at VPB in a while, but I believe it expects height values
to be referenced to the WGS84 ellipsoid. If that's the case you'll need to
convert it first to HAE.

By the way: DTED heights are referenced to the EGM96 geoid (not to the WGS84
ellipsoid). So they need conversion in order to be properly displayed. GDAL
(up until recently?) does not convey this information so there's no way for
the application to know. You just have to know :)


Glenn Waldron / @glennwaldron


On Thu, Sep 12, 2013 at 1:45 PM, Tueller, Shayne R Civ USAF AFMC 519
SMXS/MXDEC <> wrote:


Nick,

Osgdem will work with the input elevation. It will build the
database based
on the input source. For example if you're using DTED and the
geocentric
option, it will place the point at the specified elevation (in
meters) above
the ellipsoid. The point is represented in the Cartesian ECEF
geocentric
space (e.g. x,y,z).

The default ellipsoid used is WGS84. You can specify the polar and
equatorial radii in osgdem to fit to another ellipsoid. Just make
sure you
specify those radii in your EllipsoidModel class on the rendering
side so
that things match up. The EllipsoidModel class also defaults to
WGS84...

HTH

-Shayne

-----Original Message-----
From:
[mailto:] On Behalf Of
Nick Modly
Sent: Sunday, August 25, 2013 11:46 PM
To:
Subject: [vpb] osgdem and HAE/MSL

Hi,

When providing elevation data to osgdem. is it expected to be in HAE
(height
above ellipoid), or MSL (mean sea level), or can it tell from the
input? For
example, I am providing elevation data in the AIG/Arc/Info Binary
Grid
format (.adf). The data represents the elevation of the area in
meters MSL.
However, when I osgpick a point and convert it to Lat-Lon-Alt MSL,
the
altitude is off by about 30m (the difference between HAE and MSL at
this
location).

This are the options I ran osgdem with
$ osgdem --geocentric -o output.ive -l 8 -d ./path-to-dted/ -t
image.tif

Is it possible to specify a vertical datum or coordinate system,
such as
EGM96?


Thank you!

Cheers,
Nick

------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=55984#55984















------------------
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gwaldron (Glenn Waldron)
Appreciator


Joined: 25 Aug 2011
Posts: 190

PostPosted: Thu Sep 12, 2013 6:26 pm    Post subject:
osgdem and HAE/MSL
Reply with quote

Shayne,Correct, for each height value in your DTED grid, you have to sample the EGM96 geoid at that point and add the two together. That will give you HAE. I don't know of any tools off the cuff, sorry. osgEarth has vertical datum support so you could probably write a tool using that.
Glenn Waldron / @glennwaldron / osgEarth


On Thu, Sep 12, 2013 at 2:19 PM, Tueller, Shayne R Civ USAF AFMC 519 SMXS/MXDEC < (
Only registered users can see emails on this board!
Get registred or enter the forums!
)> wrote:
Quote:
Glenn,

VPB does reference to the WGS84 for the --geocentric option.

So to do the conversion, do you have to remove the contribution of the geoid
(gravitational equipotential surface) from the raw DTED first before pumping
it into VPB? Is there an application that does this?

Thanks,
-Shayne

-----Original Message-----
From: (
Only registered users can see emails on this board!
Get registred or enter the forums!
)

[mailto: (
Only registered users can see emails on this board!
Get registred or enter the forums!
)] On Behalf Of Glenn
Waldron
Sent: Thursday, September 12, 2013 12:04 PM
To: OpenSceneGraph Users
Subject: Re: [vpb] osgdem and HAE/MSL

Nick, Shayne,

I have not looked at VPB in a while, but I believe it expects height values
to be referenced to the WGS84 ellipsoid. If that's the case you'll need to
convert it first to HAE.

By the way: DTED heights are referenced to the EGM96 geoid (not to the WGS84
ellipsoid). So they need conversion in order to be properly displayed. GDAL
(up until recently?) does not convey this information so there's no way for
the application to know. You just have to know Smile


Glenn Waldron / @glennwaldron


On Thu, Sep 12, 2013 at 1:45 PM, Tueller, Shayne R Civ USAF AFMC 519
SMXS/MXDEC < (
Only registered users can see emails on this board!
Get registred or enter the forums!
)> wrote:


        Nick,

        Osgdem will work with the input elevation. It will build the
database based
        on the input source. For example if you're using DTED and the
geocentric
        option, it will place the point at the specified elevation (in
meters) above
        the ellipsoid. The point is represented in the Cartesian ECEF
geocentric
        space (e.g. x,y,z).

        The default ellipsoid used is WGS84. You can specify the polar and
        equatorial radii  in osgdem to fit to another ellipsoid. Just make
sure you
        specify those radii in your EllipsoidModel class on the rendering
side so
        that things match up. The EllipsoidModel class also defaults to
WGS84...

        HTH

        -Shayne

        -----Original Message-----
        From: (
Only registered users can see emails on this board!
Get registred or enter the forums!
)
        [mailto: (
Only registered users can see emails on this board!
Get registred or enter the forums!
)] On Behalf Of
Nick Modly
        Sent: Sunday, August 25, 2013 11:46 PM
        To: (
Only registered users can see emails on this board!
Get registred or enter the forums!
)
        Subject: [vpb] osgdem and HAE/MSL

        Hi,

        When providing elevation data to osgdem. is it expected to be in HAE
(height
        above ellipoid), or MSL (mean sea level), or can it tell from the
input? For
        example, I am providing elevation data in the AIG/Arc/Info Binary
Grid
        format (.adf). The data represents the elevation of the area in
meters MSL.
        However, when I osgpick a point and convert it to Lat-Lon-Alt MSL,
the
        altitude is off by about 30m (the difference between HAE and MSL at
this
        location).

        This are the options I ran osgdem with
        $ osgdem --geocentric -o output.ive -l 8 -d ./path-to-dted/ -t
image.tif

        Is it possible to specify a vertical datum or coordinate system,
such as
        EGM96?


        Thank you!

        Cheers,
        Nick

        ------------------
        Read this topic online here:
        http://forum.openscenegraph.org/viewtopic.php?p=55984#55984





        _______________________________________________
        osg-users mailing list
        (
Only registered users can see emails on this board!
Get registred or enter the forums!
)

http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org

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Get registred or enter the forums!
)

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S2LR
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Joined: 13 Nov 2010
Posts: 208

PostPosted: Thu Sep 12, 2013 6:31 pm    Post subject:
osgdem and HAE/MSL
Reply with quote

Good stuff to know. Thank you.

-Shayne

-----Original Message-----
From:
[mailto:] On Behalf Of Glenn
Waldron
Sent: Thursday, September 12, 2013 12:34 PM
To: OpenSceneGraph Users
Subject: Re: [vpb] osgdem and HAE/MSL

Shayne,
Correct, for each height value in your DTED grid, you have to sample the
EGM96 geoid at that point and add the two together. That will give you HAE.
I don't know of any tools off the cuff, sorry. osgEarth has vertical datum
support so you could probably write a tool using that.


Glenn Waldron / @glennwaldron / osgEarth


On Thu, Sep 12, 2013 at 2:19 PM, Tueller, Shayne R Civ USAF AFMC 519
SMXS/MXDEC <> wrote:


Glenn,

VPB does reference to the WGS84 for the --geocentric option.

So to do the conversion, do you have to remove the contribution of
the geoid
(gravitational equipotential surface) from the raw DTED first before
pumping
it into VPB? Is there an application that does this?

Thanks,

-Shayne

-----Original Message-----
From:

[mailto:] On Behalf Of
Glenn
Waldron
Sent: Thursday, September 12, 2013 12:04 PM
To: OpenSceneGraph Users
Subject: Re: [vpb] osgdem and HAE/MSL

Nick, Shayne,

I have not looked at VPB in a while, but I believe it expects height
values
to be referenced to the WGS84 ellipsoid. If that's the case you'll
need to
convert it first to HAE.

By the way: DTED heights are referenced to the EGM96 geoid (not to
the WGS84
ellipsoid). So they need conversion in order to be properly
displayed. GDAL
(up until recently?) does not convey this information so there's no
way for
the application to know. You just have to know Smile


Glenn Waldron / @glennwaldron


On Thu, Sep 12, 2013 at 1:45 PM, Tueller, Shayne R Civ USAF AFMC 519
SMXS/MXDEC <> wrote:


Nick,

Osgdem will work with the input elevation. It will build the
database based
on the input source. For example if you're using DTED and
the
geocentric
option, it will place the point at the specified elevation
(in
meters) above
the ellipsoid. The point is represented in the Cartesian
ECEF
geocentric
space (e.g. x,y,z).

The default ellipsoid used is WGS84. You can specify the
polar and
equatorial radii in osgdem to fit to another ellipsoid.
Just make
sure you
specify those radii in your EllipsoidModel class on the
rendering
side so
that things match up. The EllipsoidModel class also defaults
to
WGS84...

HTH

-Shayne

-----Original Message-----
From:
[mailto:] On
Behalf Of
Nick Modly
Sent: Sunday, August 25, 2013 11:46 PM
To:
Subject: [vpb] osgdem and HAE/MSL

Hi,

When providing elevation data to osgdem. is it expected to
be in HAE
(height
above ellipoid), or MSL (mean sea level), or can it tell
from the
input? For
example, I am providing elevation data in the AIG/Arc/Info
Binary
Grid
format (.adf). The data represents the elevation of the area
in
meters MSL.
However, when I osgpick a point and convert it to
Lat-Lon-Alt MSL,
the
altitude is off by about 30m (the difference between HAE and
MSL at
this
location).

This are the options I ran osgdem with
$ osgdem --geocentric -o output.ive -l 8 -d ./path-to-dted/
-t
image.tif

Is it possible to specify a vertical datum or coordinate
system,
such as
EGM96?


Thank you!

Cheers,
Nick

------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=55984#55984






















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