topic Re: Measuring change between shapefile attributes in ArcMap Questions

Measuring change between shapefile attributes

ZJKosel — Sat, 27 Feb 2021 18:18:52 GMT

Hello everyone,

I have two shapefiles, both of the same county, and each one is divided into about 20 subdivisions. One of these is from 2016 and the second one is from 2020. I'm trying to find a tool that would be able to measure or highlight changes in the boundaries or borders of the subdivisions within the county over time. Most things I've found are for comparing entire features instead of directly comparing attributes within two shapefiles.

I'm using ArcMap 10.6.1

Thank you,

Zachary

Re: Measuring change between shapefile attributes

DanPatterson — Sat, 27 Feb 2021 18:51:29 GMT

Find Identical (Data Management)—ArcGIS Pro | Documentation Pro

Find Identical (Data Management)—ArcMap | Documentation (arcgis.com) ArcMap

and join the result back to the original table.

What isn't identical is different

Re: Measuring change between shapefile attributes

ZJKosel — Sat, 27 Feb 2021 19:55:12 GMT

Thanks for the quick response! However, the Find Identical (Data Management) tool seems to just list the fields that have duplicates. Since I already know that all the subdivisions have slight changes in some ways to their geometry/geography, I'm trying to narrow down to where the exact locations of change are within the subdivisions of the two county shapefiles.

Thank you,

Zachary

Re: Measuring change between shapefile attributes

DanPatterson — Sat, 27 Feb 2021 20:12:05 GMT

An overview of the Data Comparison toolset—ArcGIS Pro | Documentation in Pro at least, has several difference tools.

An overview of the Overlay toolset—ArcGIS Pro | Documentation overlay options don't seem appropriate, except perhaps Intersect. Symmetrical would only be useful if there are overlaps.

Re: Measuring change between shapefile attributes

jcarlson — Sun, 28 Feb 2021 01:16:26 GMT

@DanPatterson's first link is the one you want. The corresponding ArcMap page is here.

As far as measuring the change, the output match table gives a rough idea of how close a match the features were between the two datasets, but in spite of it being given as a number, it's not really a measurement.

You can optionally get some additional fields quantifying the degree of change if you input a change tolerance buffer, but I don't always find that to be helpful. It really depends on your data, but there are times when a change in shape can be more important than a lateral shift.

If you want to look beyond shapefiles, take a look at what's known as a Hausdorff distance. You'd need your layers in a DB of some sort, but ArcGIS can export to SpatiaLite, which is a self-contained database file. SpatiaLite does support calculating a Hausdorff distance between two geometries, and can be quite useful for the "measuring" part.

Re: Measuring change between shapefile attributes

ZJKosel — Fri, 05 Mar 2021 22:01:41 GMT

Thanks for the links! I focused on other projects for a while, but when I returned to this one, the Symmetrical Difference tool did what I had in mind.

Thank you,

ZJKosel