Hi,
If all I've got is raw (ie, unrectified) aerial photography & sufficient
ground control points, what is the process for creating a DEM (assuming
it's possible with GRASS)? I've not been able to find any documentation
apart from orthorectification using an existing DEM.
Thanks,
Tim Bowden
Hi.
If all I’ve got is raw (ie, unrectified) aerial photography & sufficient
ground control points, what is the process for creating a DEM (assuming
it’s possible with GRASS)?
Are you looking to georeference an aerial image? Or create a Digital Elevation Model? Each is a different, specific task.
Mark
On Mon, Sep 9, 2013 at 10:59 AM, Tim Bowden <tim.bowden@mapforge.com.au> wrote:
Hi,
If all I've got is raw (ie, unrectified) aerial photography & sufficient
ground control points, what is the process for creating a DEM (assuming
it's possible with GRASS)? I've not been able to find any documentation
apart from orthorectification using an existing DEM.
You can find something in the Wiki
http://grasswiki.osgeo.org/wiki/Stereoscopic_analysis#GRASS_5
There is an old software "stereo" which seems to offer this, see links there.
It would be great to get this functionality into GRASS 7.
Markus
Hello Tim,
besides GRASS gis tools, perhaps the digital photogrammetric workstation
developed by Rio de Janeiro State University’s School of Engineering
could meet your needs :
There was recently a new major release.
Yours,
Vincent.
Le lundi 09 septembre 2013 à 16:59 +0800, Tim Bowden a écrit :
Hi,
If all I've got is raw (ie, unrectified) aerial photography & sufficient
ground control points, what is the process for creating a DEM (assuming
it's possible with GRASS)? I've not been able to find any documentation
apart from orthorectification using an existing DEM.Thanks,
Tim Bowden_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
On Mon, 2013-09-09 at 08:43 -0400, Mark Seibel wrote:
Hi.
If all I've got is raw (ie, unrectified) aerial photography &
sufficient
> ground control points, what is the process for creating a DEM
(assuming
> it's possible with GRASS)?Are you looking to georeference an aerial image? Or create a Digital
Elevation Model? Each is a different, specific task.Mark
Both I guess, but the DEM is the end goal; that is the bit I haven't
been able to find any docs on, and noting what Marcus has posted it
seems there's quite a bit of work to be done getting that happening.
Thanks,
Tim
On Mon, 2013-09-09 at 15:08 +0200, Markus Neteler wrote:
On Mon, Sep 9, 2013 at 10:59 AM, Tim Bowden <tim.bowden@mapforge.com.au> wrote:
> Hi,
> If all I've got is raw (ie, unrectified) aerial photography & sufficient
> ground control points, what is the process for creating a DEM (assuming
> it's possible with GRASS)? I've not been able to find any documentation
> apart from orthorectification using an existing DEM.You can find something in the Wiki
http://grasswiki.osgeo.org/wiki/Stereoscopic_analysis#GRASS_5
There is an old software "stereo" which seems to offer this, see links there.
It would be great to get this functionality into GRASS 7.Markus
Thanks Markus,
For now this capability seems to be 'missing'. Once again I'm
left wishing I was a competent c/c++ programmer (wip...).
In any event, I suspect this approach has been mostly (?) superseded by
'Structure from Motion' type modelling which I'm also playing with- was
just hoping to be able to add 'traditional' photogrammetric modelling
to my toolkit and be able to do a comparison between the two).
Regards,
Tim Bowden
On Mon, 2013-09-09 at 15:19 +0200, Vincent Bain wrote:
Hello Tim,
besides GRASS gis tools, perhaps the digital photogrammetric workstation
developed by Rio de Janeiro State University’s School of Engineering
could meet your needs :There was recently a new major release.
Yours,
Vincent.
Thanks Vincent, I'll have a good look at this. At first glance is looks
very promising.
Regards,
Tim
One of the handiest solutions for extracting 3D data
using SfM is this:
http://homes.cs.washington.edu/~ccwu/vsfm/
It includes georeferencing and can handle the coordinate
ranges that occur in geographical data. It is free
to use for non-commercial applications but unfortunately
not open source.
Anyhow, SfM works best when there is a large series
of images with a lot of overlap and small angular
displacement between consecutive images. Traditional aerial
imagery will not always give good results. There can also
be trouble with the simple camera model that some SfM
tools (including VSFM) use.
An open source solution that is optimised for remote
surveying applications is currently lacking, AFAIK.
Best,
Ben
On 09/10/2013 04:45 AM, Tim Bowden wrote:
On Mon, 2013-09-09 at 15:08 +0200, Markus Neteler wrote:
On Mon, Sep 9, 2013 at 10:59 AM, Tim Bowden <tim.bowden@mapforge.com.au> wrote:
Hi,
If all I've got is raw (ie, unrectified) aerial photography & sufficient
ground control points, what is the process for creating a DEM (assuming
it's possible with GRASS)? I've not been able to find any documentation
apart from orthorectification using an existing DEM.You can find something in the Wiki
http://grasswiki.osgeo.org/wiki/Stereoscopic_analysis#GRASS_5
There is an old software "stereo" which seems to offer this, see links there.
It would be great to get this functionality into GRASS 7.Markus
Thanks Markus,
For now this capability seems to be 'missing'. Once again I'm
left wishing I was a competent c/c++ programmer (wip...).In any event, I suspect this approach has been mostly (?) superseded by
'Structure from Motion' type modelling which I'm also playing with- was
just hoping to be able to add 'traditional' photogrammetric modelling
to my toolkit and be able to do a comparison between the two).Regards,
Tim Bowden_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user
--
Dr. Benjamin Ducke, M.A.
{*} Geospatial Consultant
{*} GIS Developer
benducke@fastmail.fm
On Tue, 2013-09-10 at 11:11 +0200, Benjamin Ducke wrote:
One of the handiest solutions for extracting 3D data
using SfM is this:http://homes.cs.washington.edu/~ccwu/vsfm/
It includes georeferencing and can handle the coordinate
ranges that occur in geographical data. It is free
to use for non-commercial applications but unfortunately
not open source.
Most of the underlying tools to that are open source, and they're what
I'm using (opensift, bundler_sfm, cmvs/pmvs etc). I've had some limited
success so far (not tried aerial imagery), but I don't yet properly
understand the work flow or all the options at various stages of the
process. I also don't understand yet how to measure the 'quality' of the
output (rather crucial). Much more experimentation needed...
Anyhow, SfM works best when there is a large series
of images with a lot of overlap and small angular
displacement between consecutive images. Traditional aerial
imagery will not always give good results. There can also
be trouble with the simple camera model that some SfM
tools (including VSFM) use.
Yes, as I understand it, each point should be in /at least/ 3 images,
preferably with about 15° difference in viewing angles between camera
positions.
An open source solution that is optimised for remote
surveying applications is currently lacking, AFAIK.
I think most of the pieces are there assuming you have the cpu & ram to
cope with the processing load but they're certainly not integrated into
a nice GUI. Also being able to 'rubber sheet' the final point cloud to
ground coordinates is not something I've found yet; Doing a '7
parameter' conversion is there, but that's not quite the same.
Idle thought: Is this something that could be worked into GRASS?
Tim Bowden