Prevent polygons from degenerating into little triangles (option) about mapshaper HOT 1 OPEN

Sometimes I want to preserve small islands by exaggerating them, basically
degrading a little bit, but inflating their shape so it is still just
larger than a dot at the new representative scale (say 6 - 12 vertices).
But most times I want to remove them completely.

I think the majority use case, though, is when a multipolygon shape
composed of many small areas, or a tiny country like Andora, still needs to
be represented when simplified else the DBF won't match with the SHP part;
and ideally the feature is still discernable. While that is useful, it's
just as useful to spin off a separate point shapefile for places like that
simplified out of representation so they can be visualized and be legible.

On Fri, Nov 22, 2013 at 3:00 PM, Matthew Bloch [email protected]:

Currently, the minimum complexity of a polygon ring is 3 unique vertices
(a triangle).

Tiny triangles aren't particularly desirable on a map. One solution would
be to let users specify a minimum of x unique vertices per shape (say, 4,
5, or 6). Island polygons could be removed after the vertex count falls
below x. The vertex count of non-removable rings would be prevented from
falling below x.

Then again, vertex count is a pretty crude way of determining if a shape
is too degenerate or too small to retain.

A better alternative might be to remove shapes whose dimensions are
smaller than a certain threshold relative to the intended output size of
your map. E.g. if you are making a map to display at 800 pixels wide,
islands smaller than, say, two pixels on their longest side could be
removed. Or you could use area: islands with areas less than 2 or 3 sq.
pixels could be removed.

This solution has its drawbacks too... we can weigh the alternatives if
people are interested in this feature.

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