Help MatchCDS

Match Crash Dummy Symbol (CDS)

The crash dummy symbol is a four quadrant calibration marker. For firenodejs, we use the "bwwb" or "first quadrant white" CDS marker (see Considerations).

firenodejs

To use MatchCDS, click more... and set the radio button for matching CDS markers:

Method

We use the match-cds.json FireSight pipeline to match the following template throughout the current camera image:

The /firesight/match-cds REST service will return a possibly empty JSON array of matched points. Each matched CDS will have the following information:

• x the CDS marker pixel x-coordinate relative to left of image
• y the CDS marker pixel y-coordinate relative to top of image
• corr is match correlation, which is between 0 and 1, with 1 being "perfect match".

Considerations

• Performance Matching a small template across a whole camera image takes time. On a Raspberry Pi 2, finding CDS markers can take about 1.75 seconds (compare with calc-offset, which takes about 0.5seconds).
• Camera height the CDS marker is fairly scale independent, and camera height is normally not an issue, even with blurry images
• CDS angle for performance, firenodejs assumes that the CDS marker is white in quadrant 1. Matching degrades rapidly if the marker is rotated. More robust algorithms are possible, but for now, watch out for this limitation. As you can see from the above picture, small angles do not affect the match.