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Contributor
Posts: 23
Registered: ‎01-30-2016
Accepted Solution

Georeference images based on XYZ GCPs points (not only XY)

Hi All,

Assuming that I have a raster image (not georeferenced) and I have 4 control points (X,Y,Z), does Erdas have the capacity to georeference that image based on X,Y,Z? not only on X,Y?

 

Best regards,

Ahmad

Regular Contributor
Posts: 215
Registered: ‎11-16-2015

Re: Georeference images based on XYZ GCPs points (not only XY)

Yes, so long as you use a sensor model or DLT as your transformation method.

Contributor
Posts: 23
Registered: ‎01-30-2016

Re: Georeference images based on XYZ GCPs points (not only XY)

Hi Johnnie,

Thanks for your input, could you please provide me with anything that might help to start? Any documentation or articles may be a great help of me

 

Thanks,

Ahmad

Regular Contributor
Posts: 215
Registered: ‎11-16-2015

Re: Georeference images based on XYZ GCPs points (not only XY)

Hiya,

 

There's help files and example work flows included in the Help section of the software, but here's a couple of links that may be useful:

 

http://bit.ly/2hUuPVa - work flow

 

http://bit.ly/2hUttK5 - background

 

Cheers,

 

Johnnie

Contributor
Posts: 23
Registered: ‎01-30-2016

Re: Georeference images based on XYZ GCPs points (not only XY)

Hi Johnnie,

Thanks for your help and support, I had the chance to look at the documentation, then I come up with the following procedure, Please have a look at it and correct me if I am wrong

 

  • select Control points for multispectral tab
  • Select DLT form geometric model
  • Then I measured the points manually, then added the X,Y,Z ref for each control point
  • Solve Geometric model
  • Resample the image
Staff
Posts: 585
Registered: ‎02-02-2016

Re: Georeference images based on XYZ GCPs points (not only XY)

Hi Ahmad,

 

That is the correct procedure. Please be aware that at least 6 GCPs points are needed to solve the DLT model. This 3D model requires that GCPs are well distributed across the image horizontally and vertically. After the model is solved you should check your RMS error before resampling.

 

Kind regards,

 

Stephen Bent

Hexagon Geospatial Support

Contributor
Posts: 23
Registered: ‎01-30-2016

Re: Georeference images based on XYZ GCPs points (not only XY)

[ Edited ]
 
Contributor
Posts: 23
Registered: ‎01-30-2016

Re: Georeference images based on XYZ GCPs points (not only XY)

Thanks Guys, this was really helpful, I have attached a manual that I have developed for knowledge sharing, but I wonder if I can show the Z value for the georeferenced image just to make sure that everything is ok.

 

Best regards,

Ahmad

Highlighted
Regular Contributor
Posts: 215
Registered: ‎11-16-2015

Re: Georeference images based on XYZ GCPs points (not only XY)

 Nope, you can't. However, using the z values should have helped constrain the model so checking the x,y coordinates (prefereably against stand alone check points) will show you the true accuracy of your georeferencing.

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