Photogrammetry

Precision Measurement with Target Marks

ELCOVISION 10 can use targets to measure single, precisely defined points with maximum accuracy. While automatically measured natural points have a measurement accuracy of about 0.2 to 0.5 pixels in the image, targets exceed this with an impressive 10 to 100-fold increase in accuracy on average. This precision in image measurement results in equally accurately determined object points, whereby point accuracies in the sub-millimetre range can be achieved almost effortlessly.

The typical measurement accuracies behave as follows for different target mark diameters D:

Diameter D Centre circle


Typical accuracy with which the centre of the target mark is measuredTypical(*) point accuracy with a pixel size of 1mm on the object
20 – 30 Pixel75% better than 0.1 Pixel
38% better than 0.05 Pixel
10% better than  0.01 Pixel
75% better than 0.075mm
38% better than 0.037mm
10% better than 0.007mm
30 – 40 Pixel82% better than  0.1 Pixel
48% better than  0.05 Pixel
20% better than  0.01 Pixel
82% better than 0.075mm
48% better than 0.037mm
20% better than 0.007mm
40 – 50 Pixel88% better than 0.1 Pixel
55% better than 0.05 Pixel
25% better than 0.01 Pixel
88% better than 0.075mm
55% better than 0.037mm
25% better than 0.007mm
*  When using a higher quality camera/lens combination and good image quality, 4-6 image measurements per target mark and good image capture configuration..

If the images are made in such a way that a target mark is visible in at least 8 images, the few "outliers" with poor image measurement accuracy can be identified and deleted using the global orientation, object point accuracies of better than 0.05mm are relatively easy to achieve.

Application Examples for Target Markers:

ELCOVISION 10 recognises 2 versions of targets, V1 and V2:

Targets V1

  • Suitable for relatively poor image quality such as noisy, slightly blurred, underexposed or overexposed image.
  • 12 bit barcode: 47 different targets.

Targets V2

  • Need good image quality.
  • 16 bit barcode: 800 different targets.

All target marks as PDF and DWG for printing on labels, various Hama, Zweckform, Avery labels are supported.

https://www.elcovision.com/Marker/TargetV1V2.zip

 

Calibration fields in A0, A1, A2, A3, A4, A5, A6 with control point coordinates for the pages. Suitable for medium precision camera calibrations.

https://www.elcovision.com/Marker/TargetKalib.zip

ELCOVISION 10 crime scene rulers in various sizes for the precise measurement, rectification and documentation of small traces such as fingerprints.

https://www.elcovision.com/Marker/TargetRuler.zip