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2019-09-29 12:19:00 -0500 received badge  Student (source)
2015-08-18 01:16:58 -0500 asked a question Best pattern/method for low resolution marker detection

Hi All,

Long time reader, first time poster.

I am trying to design and detect a marker that can be identified from as little as 20x20 pixels out of a 20MP photo (for aerial surveying purposes). Orientation is not fixed, and I need to design such that there are >15 unique colour combinations to determine unique targets.

My thinking so far is a circular black rim, then a smaller, concentric white rim, then four quadrants of colour (R,G,B,Black) inside that white, inner circle. Black will be in the same spot and act as an anchor. This combination works at about 30x30 px but my houghcircles python script struggles, detecting pretty much everything else except these markers at 20x20.

Does anyone have some experience in low DPI detection? I see lots on checkerboards, edges, etc, but the minimum feature size must be significant to not have cameras just smear out the information.

Any advice would be appreciated...