Problems with 57 degree FOV camera and accuracy

[Timbecile]

Hi,

We've got a 6 camera setup using the v100R2 3.5mm cameras and Tracking Tools 2.2.1. Everything is running great, but when we place a trackable in the space, the software reports a position that is not accurate. When the trackable is held at 39" (1 meter) above the ground, instead of reporting the position as 1 meter, it reports it as 0.8 meters.

This scale issue is also occuring along the X and Z axes. We have previously used a similar setup with the standard field of view cameras where these values were accurately reported.

During the calibration process, we set the lens type to 3.5mm (wide), but this doesn't seem to correct the issue. Is there another setting that we're missing, or another step in the calibration process that will fix this?

[NaturalPoint - Mike]

What is the measured distance in mm between the centers of the outside markers of your wand?

[Timbecile]

they're about 500 millimeter, but under Wand Acquisition settings in the calibration tab, we're using the default Wand Length of 400. should this be set to 500?

[NaturalPoint - Mike]

Yes. The system uses that input value and compares it to the wand to determine scaling. If the system thinks the wand is 400mm, and actually gets calibrated with a 500mm wand, everything will be decreased in size by about 20% as a result of the improper scaling. This seems to fit perfectly with the .8m reading when holding a marker 1m off the ground.