Supporting custom frame cameras in the ENVI Orthorectification Module

The ENVI Orthorectification Module supports digital aerial image files from the UltraCam, DMC, and Applanix frame-central cameras. It also supports data from the Leica ADS40 line-scanner camera. You can add support for other frame cameras by creating an exterior/interior orientation description of your frame camera in the form of an XML file. This help article demonstrates how to do this.

The data directory containing the aerial image files (typically .TIF files) should contain one XML file per image file. The root names of the image file and corresponding XML file should be the same. Users should first open the aerial image file in ENVI. Then select the Rigorous Orthorectification tool. In the first step, click the + button in the Input Images section to select the aerial image file for input. Upon clicking Next in the Wizard, ENVI will look for, and parse, the corresponding XML file, in order to read the camera data.

Please refer to the following document for additional information:

Spacemetric, 2013. Keystone Image File Formats User Manual

 

DMC Aerial Frame Camera example:

A sample XML file for the DMC aerial sensor can be downloaded here.

Below is a short explanation about the information in the XML file:

The first section describes the camera and contains information from the camera calibration. Since  DMC images are processed to be "distortion free", only the focal length and an affine transformation are needed:

<CameraData>
   <CameraId>DMC</CameraId>
   <FocalLength>0.12</FocalLength>
   <FocalPlaneAffine>
       <X0>-0.04608</X0>
       <X1>1.2E-5</X1>
       <X2>0.0</X2>
       <Y0>0.082944</Y0>
       <Y1>0.0</Y1>
       <Y2>-1.2E-5</Y2>
   </FocalPlaneAffine>
</CameraData>

The camera Id could in this case be DMC01-0025

The focal length and the parameters in the FocalPlaneAffine are given in meters. They could also be given in the unit pixels instead. In that case it would look like this (with a more compressed layout):

  <FocalLength>10000</FocalLength>
   <FocalPlaneAffine><X0>-3840</X0><X1>1</X1><X2>0.0</X2><Y0>6912</Y0><Y1>0.0</Y1><Y2>-1</Y2></FocalPlaneAffine>

The next section, CameraMount, is not mandatory and does not contain any information in this case.

    <CameraMount>
        <Omega>0.0</Omega>
        <Phi>0.0</Phi>
        <Kappa>0.0</Kappa>
    </CameraMount>

The last part contains the information of one, or many, images.

    <ImageData>
       <FileName>ImageFileName_5.tif</FileName>
        <ImageId>ImageID_5</ImageId>
        <Crs>3006</Crs>
        <X>643745.55939</X>
        <Y>5014812.66043</Y>
        <Z>3029.51311</Z>
       <Omega>-0.11083663779880237</Omega>
       <Phi>-0.2596184743006365</Phi>
       <Kappa>90.44067376952215</Kappa>
    </ImageData>

The filename is the file path relative to the xml file.

The ImageId is the ID of the image that will be used in Keystone.

Crs is the EPSG code of the map projection used.

X,Y,Z describe the position given in the unit of the map projection.

Omega, Phi, Kappa are attitudes in degrees.

Reviewed 9/26/2014 MM