Question

I’m working on an app that lets users select regions by finger painting on top of a map. The points then get converted to a latitude/longitude and get uploaded to a server.

The touch screen is delivering way too many points to be uploaded over 3G. Even small regions can accumulate up to ~500 points.

I would like to smooth this touch data (approximate it within some tolerance). The accuracy of drawing does not really matter much as long as the general area of the region is the same.

Are there any well known algorithms to do this? Is this work for a Kalman filter?

Answer 1

There is the Ramer–Douglas–Peucker algorithm (wikipedia).

The purpose of the algorithm is, given
a curve composed of line segments, to
find a similar curve with fewer
points. The algorithm defines
‘dissimilar’ based on the maximum
distance between the original curve
and the simplified curve. The
simplified curve consists of a subset
of the points that defined the
original curve.