topic Re: Point to Polygon distance in Geoprocessing Questions

Point to Polygon distance

PaulaMcNamara — Wed, 26 Oct 2011 23:31:51 GMT

Hi,
I have 2 layers:

Point layer of outlets

polygon layer of outlet catchment area

There is an outlet_ID attribute on both layers. Several polygons in the catchment layer make up the catchment for one outlet, so there will be several polygons with the same outlet_ID.

The outlet point is not necessarily in the middle of the catchment area.

Is it possible to work out the distance from the outlet point to the farthest edge of the catchment?

thanks
Paula

Re: Point to Polygon distance

markdenil — Thu, 27 Oct 2011 11:20:51 GMT

You don't really want a Point To Polygon distance, but a Point To Point distance, with the second point being the polygon vertex furthest removed from the outlet point.

make a loop to cycle through your outlet points. For each:

create layers of (1) just one outlet and (2) just the corresponding catchment polygons.

use the verticies to point tool (needs ArcInfo, I am afraid) to convert the polygon(s) to vertex points

use the near table tool to get the distance (and direction, if you want that too) of all these points from the outlet

select the point in the near table furthest from the outlet to get the greatest distance (and direction) from that outlet.

blow away the layers and point table; then do the next outlet point.

Re: Point to Polygon distance

PaulaMcNamara — Thu, 27 Oct 2011 23:40:56 GMT

Thanks Mark, that makes sense. I have 9.3.1 ArcInfo...phew.

I'll have to get a python wiz to get a loop sorted for me.

Thanks for your help

Paula