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Valued Contributor
Posts: 517
Registered: ‎10-27-2015
Accepted Solution

Using SGM with historical frame camera images

I have a .blk with two historical frame camera images. I have already done the triangulation and I have tie points and GCP. 
I would like to use SGM with this images. I know that it is not possible. I'm looking for a workaround. Can I create a new blk with digital camera as sensor and then load the frame camera images and the points? Will it work?

Thank you


Regards

Staff
Posts: 213
Registered: ‎10-21-2015

Re: Using SGM with historical frame camera images

Hello,

 

Have you considered using classic ATE or eATE terrain extraction tools instead of SGM? Both will generate a surface using frame sensor geometric model. eATE can also generate a dense point cloud. You won't need to create a new digital camera block file if you use eATE.

 

As per your question it may work. You need well distributed highly accurate GCPs. If your triangulation results are good with frame camera block file, you may turn the tie points into GCPs and import them in digital camera block that you will generate from scratch.

 

For frame cameras interior orientation of the camera is defined by fiducial marks, and you will lose this information.  You need to define a new camera file, you may use focal length and principal point coordinates that are given in the camera calibration report. You need to compute the pixel size.  First check your camera calibration report, in some calibration reports  principal point coordinates are given both in pixels and millimeters. Using these values you may compute the relation between pixels and mm. Actually every other value given in pixels and mm should have the same scale difference. You can also compute the pixel size from solved interior orientation of the frame camera using film and image coordinates. 

 

Best Regards,

Yasemin

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

Re: Using SGM with historical frame camera images

[ Edited ]

Just to give you added confidence, one of my customers has successfully used XPro SGM with analogue data essentially using the process Yasemin described. He had to make a best guess as to pixel size and then performed a space resection to account for that unknown. Good ground control is a must.  He got really good dense point matching. Cheers, Johnnie

Valued Contributor
Posts: 517
Registered: ‎10-27-2015

Re: Using SGM with historical frame camera images

Thank you all for your reply!

So these are the information I have...which is the correct calculation I have to do?

thank you

 

Interior_orientation.JPG

Highlighted
Staff
Posts: 213
Registered: ‎10-21-2015

Re: Using SGM with historical frame camera images

Hello,

 

I computed the pixel size in x=66.86 microns and in y=65.95 microns. I computed the distance between fiducial 2-1 in pixel and in image coordinate systems then I computed the relation between pixel and mm to find the pixel size in x. Similarly I used the distance in y between fiducials 3-4 to compute the pixel size in y.

 

Alternatively, you may open the block file with interior orientation calculated for the frame in HFA Viewer as shown in the screen capture below, the numbers are already there (via HFAView, 2.5044427823076296e-002 mm for x, 2.5053843378096682e-002 mm for y). 

 

HFA.png

 

Best Regards,

Yasemin

Valued Contributor
Posts: 517
Registered: ‎10-27-2015

Re: Using SGM with historical frame camera images

Thank you very much!!

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