If you have fiducials but NO coordinates:
- Measure between each set of fiducials along the edge of the photo, in mm. Use the "Compute from Length" button and enter the four lengths.
If you have NO fiducials but do you have a cross marking of the photo center:
- Measure the distance from photo center to each edge, in mm. Use the corner pixels of the photo as fiducials and enter the following coordinates for the camera calibration information as fiducial coordinates:
Top Right: X=X2 Y=Y1
Bottom Right: X=X2 Y=-Y2
Bottom Left: X=-X1 Y=-Y2
If you have NO fiducials, and NO photo center:
- Measure the length of each side of the photo using "Compute from Length" in the Camera Calibration panel - "Fiducial Coordinates" section. Enter your measurements, in mm. Use the image corners as the fiducials.
Focal length of the camera is unknown:
If the focal length of the camera is unknown, there are a few different things you can try:
- Most older cameras were constructed with 6", 8" or 12" focal lengths. A first approach would be to try each of these. If you do not have the right focal length, the resulting flying height will be way off, and you will have remaining distortions in the imagery.
- Publications such as the "ASPRS Manual of Photogrammetry" list photogrammetric cameras through history, with frame sizes and nominal focal lengths. If you have an unusual frame size i.e., not 9"x 9", this would be a valuable tool.
- Create the project and import the imagery.
- Import the GPS/INS data for all available photos.
- Enter GCPs, if desired.
- Enter at LEAST Tie Points (manually) and GCPs if possible, for any photos which do not have GPS/INS. The auto tie point can only operate if there is an initial approximation for where each photo is. Otherwise, it won't know what photos to match with.
- Run auto tie point.
The auto fiducial collection will run successfully for any combination of orientations. However, the calibration edge has to be set manually. There is no automatic way to do this, since the digital image can be in any orientation. So, you have two options:
- Run the automatic fiducial collection on the raw images, and then manually change the calibration edge for the affected photos.
- Rotate the images to a common orientation using the batch rotate function before running the auto fiducial collection. The calibration edge does not need to be adjusted in this case.