Built in distance calculations?

[Greg McKaskle]

In reality, all of these methods are pretty imprecise. Encoders on drive wheels cannot account for slip or sideways motion due to a collision with field or another robot.

The camera method works by knowing the real-world size of the target. At a given distance, the target should measure the same pixel size. Moving closer to the target increases the pixel size, and moving farther decreases. You can think through the symmetric triangles or use trig if you like, but estimating distance based on the perceived size of a known object is a pretty accurate approach. The thing that can cause moderate error is if the vision selects the inner circle rather than the outer error to base the distance computation.

The best way to determine the error is to measure it. Determine if it is accurate enough for what you need and determine if other approaches are more accurate.

Greg McKaskle