orthorectification aerial photographs - NV5 Geospatial

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Last Post 27 Feb 2009 06:06 AM by anon

orthorectification aerial photographs

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anon

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27 Feb 2009 06:06 AM
Dear list, We have aerial photographs of the '30s and want to orthorectify them in ENVI. We have no camera information available. Are we doing the right thing if we use the build RPC function and subsequently use the orthorectify using RPC function? Or is there a possibility to orthorectify them without knowing the focal length of the imagery etc? At present we tried the first method, but got an error message saying that the interior and exterior information are not accurate enough for orthorectification. Can someone give us information on the accuracy the GCP's and fiducials should have to allow orthorectification? At present the RMS error of the fiducials is about 3 and for the GCP's about 1. Or can tell us how we can orthorectify such imagery in ENVI? thanks, Véronique

MariM

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27 Feb 2009 08:04 AM
Currently, orthorectification in ENVI is only done through RPCs but any sort of orthorectification is going to require knowledge of the sensor or camera. I have not seen the warning message regarding the information not being accurate enough, so I suspect what it says is true. Usually, RMS is quite small when you save the RPCs to the file in the final dialog. In the GCP dialog, an error of 1 or less (depending on the resolution of the data) is desirable. I am wondering if it might be the camera information that is insufficient.

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