How to resize a polygon in km?

Question

I have a polygon on my map and I want to resize it in that way I add X km to all of the vertexes. Any idea?

Resize relative to what? Adding N kilometers to the y dimension and the x dimension of every vertex will simply move the polygon farther away from the zeropoints of the x and y axes of the projection (for latitude, the equator, for example). — MappingTomorrow, Jan 30 '13 at 21:50
You do realise that for most polygons this will result in a modified shape? — lynxlynxlynx, Jan 30 '13 at 21:52
I want to do the same like this:
obj.geometry.resize(2, obj.geometry.getCentroid() );

instead of 2 there will be x-km. I'm sorry for the misunderstanding... — user14734, Jan 30 '13 at 22:17

score 3 · Answer 1 · answered Jan 30 '13 at 21:56

3

The spatial operation you need is called BUFFER and is implemented in most geographical database managers

answered Jan 30 '13 at 21:56

Jose Paredes

+1 for this answer... although a general question is, why don't you just redraw the polygon to the specifications that you want? – Andy TIce Jan 31 '13 at 05:03

score 1 · Answer 2 · answered Jan 31 '13 at 07:53

1

if you use geodjango on server side, you can use buffer method in Topological Methods.

polygon.buffer(1000) # 1 km buffer for your polygon

i hope it helps you...

answered Jan 31 '13 at 07:53

urcm

2 Answers2