topic Re: Subtracting a feature in Geoprocessing Questions

Subtracting a feature

GuyCunningham — Fri, 27 Jul 2012 17:38:17 GMT

I am attempting to determine what streets in my city are poorly lit. To achieve this, I have a polygon shape file of all of the city's streets. In addition, I have run a 75 foot buffer around all of the streetlights in the city. While intersect is a great tool to see which streets are well lit (intersect the buffer and the streets), I want the opposite - the streets that are NOT contained within the buffer. Is there a simplistic way to do this? I could probably use union but I do not want to delete 1000+ polygons by hand.

FYI - I have ArcInfo 10.1

Re: Subtracting a feature

LucasDanzinger — Fri, 27 Jul 2012 20:07:36 GMT

I think you might want the Erase tool.

Re: Subtracting a feature

GuyCunningham — Mon, 30 Jul 2012 14:56:22 GMT

That is what I'm looking for, but I do not have the Desktop Advanced license required. Is there a way to do a similar function with a Desktop Basic license?

Re: Subtracting a feature

BruceHarold — Mon, 30 Jul 2012 15:57:18 GMT

That is what I'm looking for, but I do not have the Desktop Advanced license required. Is there a way to do a similar function with a Desktop Basic license?

Hi

You can mimic Erase with a little effort. First Clip your streets polygons usng your Lights polyons, then Union the output of this with the original Streets polygons.
The features with a clip output FID of -1 are what Erase would output.

Regards

Re: Subtracting a feature

LucasDanzinger — Mon, 30 Jul 2012 15:57:53 GMT

I see, I thought you had ArcInfo (Advanced) based on your original post. There isn't really a way to do it out of the box if you aren't at this license level. You could search through ArcScripts to see if there are any user submitted scripts that do a similar function.

Re: Subtracting a feature

GuyCunningham — Mon, 30 Jul 2012 18:38:09 GMT

I see, I thought you had ArcInfo (Advanced) based on your original post. There isn't really a way to do it out of the box if you aren't at this license level. You could search through ArcScripts to see if there are any user submitted scripts that do a similar function.

My apologies, I thought ArcInfo was the basic version. I must have got the three tiers confused.

Bruce, I will try your method. I actually came up with an additional method which I'll try and share my results.

Re: Subtracting a feature

GuyCunningham — Mon, 30 Jul 2012 18:58:03 GMT

Success!

Luckily, I marked the street lights by an attribute, so I was able to run a union of the street light buffer and the streets, then selected all of the street lights from the attribute and deleted all selected. I will try Bruce's method tomorrow, my shift just ended 😉

Re: Subtracting a feature

DanLee — Mon, 30 Jul 2012 21:19:03 GMT

You may skip the Clip step in Bruce's post.
And you don't need to mark the street lights (buffers) by an attribute, because Union gives you the street light buffer FIDs.

- Run Union to combine Buffers with Street polygons.
- Select features with buffer-FID greater or equal to 0 (not -1) and delete them; what's left are the streets you want.