topic Re: Alter point field based on another layer in New to GIS Questions

Alter point field based on another layer

RobertHogwood — Fri, 29 Aug 2014 16:38:57 GMT

I performed a network analysis to create a series of polygons based on distances (100, 200, 300m etc) around facilities for a project I'm working on. I also have population weighted centroids (point data) that I want to be given a value for a new field based on which polygon they fall under. For example, all centroids which fall in the 500m polygon from a facility would be given a 'poor' value for Access.

Is there an easy way to do this?

Thank you.

Re: Alter point field based on another layer

JorgeOrellana — Fri, 29 Aug 2014 19:16:25 GMT

Spatial Join should do the trick. First assign your polygons the categories that you need (i.e. Poor, Fair, Good, Excellent etc). Once you have that set your Target Features to your points and your Join Features would be your polygons. Your out put will now have the points with the values that you assigned the polygon they are in.

Re: Alter point field based on another layer

RobertHogwood — Sun, 31 Aug 2014 18:41:24 GMT

Thank you for the reply. Before I test this I just want to ask one more thing - is it possible to give points that don't fall within any of the polygons a value of 'no access' for example?

Re: Alter point field based on another layer

RobertHogwood — Mon, 01 Sep 2014 17:12:18 GMT

I tried it out and it seems that all points which do not fall within the polygons are deleted. Is it perhaps possible to give all blank/null space on the shapefile a specific value?

Re: Alter point field based on another layer

RobertHogwood — Mon, 01 Sep 2014 17:46:42 GMT

I found a way to accomplish the task by creating a new shapefile, drawing a shape and clipping it to the area I'm using. Then I used the erase tool to remove the exisiting polygons from the newly created shape, leaving only the previously blank areas filled by the shape. I appended it to the polygons.

Thanks for the help