To use Coded Targets in your scene or on your object to assist with automation of the marking and referencing process you would:
• Study your scene or object and decide which points you want to be targeted and which should be coded (you can mix coded and non-coded targets in the same project and on the same image, but you cannot mix RAD Targets with non-ringed coded targets in the same project).
• Estimate the scene size and determine the maximum distance between a camera and a target. This information together with your camera resolution and focal length of lens will tell you how big the center dot of the target needs to be. See Target Size and Appearance.
• Print out a set of targets and cut them up. Perhaps mount them on cardboard. You can also send out the postscript file to get the targets manufactured out of more robust materials. Coded Targets can be printed from PhotoModeler using the Create Coded Targets Dialog.
• Place the targets in your scene at strategic locations and with good coverage. When placing targets on your object or in your scene, try to affix the targets so that they are as flat as possible. PhotoModeler can tolerate slight warp in the target, but if the inner dot’s plane is too different from the outer ring plane, miscoding can occur. Using rigid paper or material can help maintain a flat target.
• Photograph your scene so that each target appears in at least two photographs from good angles. Also, make sure that targets are placed in the scene such that they are not too distorted due to perspective. PhotoModeler can tolerate perspective distortion in circular targets, but the more perspective in the images’ targets, the higher the likelihood of mis-codings/mismarkings. Try to include photos that are taken as directly towards the targets as possible to ensure they are recognized and coded properly.
• Start a standard PhotoModeler project with a calibration camera and load your images.
• Use Automatic Target Marking to automatically detect, sub-pixel mark and reference the coded targets in the image. You can also use the sub-pixel target marker to manually mark individual coded targets. See Sub-pixel Target Marking.
• If sufficient points have been referenced (at least six targets recognized on two or more photos) you can then process the project.
• Add additional points, targets and features using a combination of manual marking, sub-pixel marking, automatic marking, automated and manual referencing etc., until your project is complete.
See also Targets - Do’s and Don’t’s for tips on using targets in your project.