Ortho-rectification from GCPs

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Ortho-rectification from GCPs

inglada
Hi,

I have a SAR (Sentinel-1 from ESA image for which 252 GCPs are provided in the GeoTIFF file.
I would like to perform an ortho-rectification, but I don't know which
is the recommended way of doing so.

Since the SAR geometry is very different from the one of an optical
sensor, using the RPC solver to build an RPC sensor model produces
artifacts in the result.

On the other hand, I have a large amount of GCPs (row,col <--> lon,lat,Z)
which are well spread over the scene (they are actually a regular grid
generated with the real sensor model which I don't have access to).

Using "ossim-info -p -i" I get the output in the attached file.




I have tried using GeometricSarSensorModel from OSSIM plugins and
optimizing the model from the GCPs, but I don't understand how to create
a model from scratch.

Can you suggest an approach to solving this problem?

Thank you.

Jordi

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Re: Ortho-rectification from GCPs

Andyjo
Jordi,

I’d suggest creating an elevation source from your GCPs, geotiff, or other file type that ossim can ingest (others might have a better way to just import a csv grid of some sort, or at least convert it).

Then you can add the elevation source to the elevation database via your OSSIM_PREFS_FILE.

-Andy


> On Jun 10, 2015, at 3:20 AM, Jordi Inglada <[hidden email]> wrote:
>
> Hi,
>
> I have a SAR (Sentinel-1 from ESA image for which 252 GCPs are provided in the GeoTIFF file.
> I would like to perform an ortho-rectification, but I don't know which
> is the recommended way of doing so.
>
> Since the SAR geometry is very different from the one of an optical
> sensor, using the RPC solver to build an RPC sensor model produces
> artifacts in the result.
>
> On the other hand, I have a large amount of GCPs (row,col <--> lon,lat,Z)
> which are well spread over the scene (they are actually a regular grid
> generated with the real sensor model which I don't have access to).
>
> Using "ossim-info -p -i" I get the output in the attached file.
>
> <ossim-info.txt.gz>
>
> I have tried using GeometricSarSensorModel from OSSIM plugins and
> optimizing the model from the GCPs, but I don't understand how to create
> a model from scratch.
>
> Can you suggest an approach to solving this problem?
>
> Thank you.
>
> Jordi
> ------------------------------------------------------------------------------
> _______________________________________________
> www.ossim.org
> Ossim-developer mailing list
> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/ossim-developer

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Re: Ortho-rectification from GCPs

Oscar Kramer
In reply to this post by inglada
Jordi,

There is an ossimSarModel in ossim core (ossim/src/ossim/projection/ossimSarModel.cpp). This is a rigorous model that works for either slant or ground plane. It might be what you need. I would definitely give it a look.

Oscar


From: Jordi Inglada <[hidden email]>
To: [hidden email]
Sent: Wednesday, June 10, 2015 3:20 AM
Subject: [OSSIM] Ortho-rectification from GCPs

Hi,

I have a SAR (Sentinel-1 from ESA image for which 252 GCPs are provided in the GeoTIFF file.
I would like to perform an ortho-rectification, but I don't know which
is the recommended way of doing so.

Since the SAR geometry is very different from the one of an optical
sensor, using the RPC solver to build an RPC sensor model produces
artifacts in the result.

On the other hand, I have a large amount of GCPs (row,col <--> lon,lat,Z)
which are well spread over the scene (they are actually a regular grid
generated with the real sensor model which I don't have access to).

Using "ossim-info -p -i" I get the output in the attached file.




I have tried using GeometricSarSensorModel from OSSIM plugins and
optimizing the model from the GCPs, but I don't understand how to create
a model from scratch.

Can you suggest an approach to solving this problem?

Thank you.

Jordi

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Re: Ortho-rectification from GCPs

inglada
Hi,

Thanks for all the answers. In the meantime, a colleague suggested that
I use gdalwarp with the thin plate splines option and this does exactly
what I need now.

However, I have looked at the ossimSarModel, but I don't see how I can
used the GCPs to estimate its parameters. I don't need this now, but I
would be interesting in knowing if this would be feasible.

Thanks again.

Jordi

Oscar Kramer <[hidden email]> wrote:

>
> Jordi,
>
> There is an ossimSarModel in ossim core (ossim/src/ossim/projection/ossimSarModel.cpp). This is a rigorous model that works for either slant or ground plane. It might be what you need. I would definitely give it a
> look.
>
> Oscar
>
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------
> From: Jordi Inglada <[hidden email]>
> To: [hidden email]
> Sent: Wednesday, June 10, 2015 3:20 AM
> Subject: [OSSIM] Ortho-rectification from GCPs
>
> Hi,
>
> I have a SAR (Sentinel-1 from ESA image for which 252 GCPs are provided in the GeoTIFF file.
> I would like to perform an ortho-rectification, but I don't know which
> is the recommended way of doing so.
>
> Since the SAR geometry is very different from the one of an optical
> sensor, using the RPC solver to build an RPC sensor model produces
> artifacts in the result.
>
> On the other hand, I have a large amount of GCPs (row,col <--> lon,lat,Z)
> which are well spread over the scene (they are actually a regular grid
> generated with the real sensor model which I don't have access to).
>
> Using "ossim-info -p -i" I get the output in the attached file.
>
> I have tried using GeometricSarSensorModel from OSSIM plugins and
> optimizing the model from the GCPs, but I don't understand how to create
> a model from scratch.
>
> Can you suggest an approach to solving this problem?
>
> Thank you.
>
> Jordi
>
> ------------------------------------------------------------------------------
>
> _______________________________________________
> www.ossim.org
> Ossim-developer mailing list
> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/ossim-developer

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