Camera Calibration with Mobile Datasets
Mobile datasets will almost always require the Ladybug Sensor Orientation to be solved. This is because the Ladybug is not permanently fixed to the IMU, and is typically mounted onto an aluminum roof rack before data collection, thus the rotations from IMU to Ladybug vary with each collection.
Typically, SpatialExplorer will prompt you to create receptor masks upon opening the PLP file for the first time; however, if you did not create masks then, make sure you create masks before attempting to calibrate the camera.
Before calibrating the Ladybug, it is recommended that you create Intervals specifically for Ladybug calibration. Ideal Ladybug intervals look like a crosshatch, where two sets of opposing passes meet at an intersection:
If a crosshatch drive pattern is not present in your dataset, at minimum you want intervals that see the same content but from opposite directions (e.g. one interval driving up a street and one interval driving down the same street).
To calibrate the Ladybug, navigate to CameraSnap - SpatialExplorer will automatically detect that you are calibrating a Ladybug and will load CameraSnap parameters accordingly:
The default values will typically work well to calibrate the Ladybug orientation; however, ensure that you select your specific set of intervals used for camera calibration in the Photos dropdown menu:
To speed up camera calibration, consider using the ORB implementation, rather than SIFT. Both ORB and SIFT are feature detectors; however, SIFT typically finds about 20x as many features as ORB. While more features can sometimes be beneficial, often times it is not worth the increased processing time. ORB performs particularly well with mobile datasets and completes in less time than SIFT.
The Ladybug images contain their own lens distortion calibration, so you should see all zero values under the Distortion and Vignetting section of the calibration:
Ensure that you load the Ladybug factory calibration from the images before colorizing, via Camera Settings->Tools->Load factory ladybug calibration. This step typically completes almost instantly.
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