How to determine the changes between two polygon shapefiles of similar data

[WhitneyNewcomb]

The city I work for gets its parcel data from the county once a month so we have several years of almost the same data. I want to be able to determine where changes occur between every new month. So what are the changes between September to October, October to November, etc. And by changes I mean any change in geometry (like parcel splits or merges) or changes in attributes (especially changes in ownership).

I've contacted ESRI about this and they weren't able to do a whole lot for me. 

Here's what I've tried so far:

I am able to find changes in geometry by using the Select by Location: Identical features and inverting the selection. 

This works fine but does not get me changes in attributes.

I would use the Feature Compare tool but this does not work as it requires the same number of rows in both tables - which I don't have. 

I also found an old arcgisscripting tool and converted it to arcpy and it worked with point datasets (but at a certain point in time the County changed how they did their parcel data and went to polygons only which the script does not work with).

So I'm at a loss for what to do now.

Does anyone have any advice for me?

Please let me know if there's any info I can give to help you help me.

-Whitney Newcomb

[WhitneyNewcomb]

Hi Dan,

Let me just check with my higher-ups and make sure I can share the data. It shouldn't be a problem and I'll email you ASAP.

Also, Could you elaborate on how the spatial joins will show me these differences? Thank you.

[DanLee]

Great! I look forward to your sample data. Thanks again for sharing the data and for your time.

Spatial Join tool allows you to join 1-to-1 or 1-to-many; you can choose one of many Match Options, such as INTERSECT, CONTAINS, HAVE_THEIR_CENTER_IN, etc. If a polygon in Oct data Is split into 3 polys in Nov. data, the tool will find the relationship. If you choose 1-to-1 join, you will get a Join Count field with the value 3. If 2 polys are merged, the two polys will join the same merged poly. There are other tools to analyze duplicates, e.g. Find Identical, Frequency.

[LindaRadomile]

Hi Dan, 

Has there been any movement on this tool?  We too are looking for a polygon comparison to highlight additions, removals, or modifications.

[DanLee]

Hi Linda,

I would still like to ask for your data, if possible, to see the specific case. I did help Whitney to solve the problem he faced once I got his data; he actually had common attributes between the two sources, so Add Join followed by Select Layer By Attribute did the trick. Would you be able to share sample data? You can email to dlee@esri.com

Thanks,

Dan

[LLyons]

Hi Dan,

Just wondering if there has been any updates? I'm trying to identify the changes between the 2010 Census TIGER boundaries and the 2020 Census TIGER boundaries. Thanks!

[JosephCornellisson]

Dan

Has any work been done on this polygon comparison tool. I have a similar situation trying to compare two parcel data sets that have changed over time

thanks

Joe 

[DanLee]

Hi Joe,

Thank you for checking. The short answer is no, we have not developed this tool/option yet. Part of the reasons is that we are still researching on use cases, not only parcel polygons but also other features, in order to fully understand the spectrum of scenarios and to see what's in common for a tool design.

Would you be able to share your parcel data with me? Could you describe in what way the two data sets are different, e.g. are they mostly identical except the changed features; do they have common attributes/IDs, such as APN?

Thanks,

Dan

[JosephCornellisson]

Dan

Unfortunately I am not the owner of the data, just a user. It is considered

proprietary data. I will check with them but I am not hopeful.

Please call and I can give you the use case.

Joe

Joseph Cornellisson

Geologist/GIS Manager

Division of Minerals Evaluation

Appraisal and Valuation Services Office (AVSO)

U.S. Department of the Interior

Denver Federal Center, Bldg 46, Suite 102

PO Box 25247

One Denver Federal Center

Denver, CO 80225

Phone: 303-969-5941

Fax: 303-969-5949

E-mail: Joseph_cornellisson@ios.doi.gov <Joseph_Cornellisson@ios.doi.gov>

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[GuillermoMarinez1]

Hi, i have the same problem, i am going to implement the folowing process in model builder. When i finished the model i will share them.

looking for the solution i found an tool in datainteroperability that perform the "change detector" operation, if one have this extension can find the diferences between two featureclass.

[deleted-user-_ZI9nJL9TGxh]

Hello Guillermo, 

Might your model merit a script that searches the tables to compare for changes in the APN before it finds spatial changes?  We are working on that angle.  My colleague and I are using the Union tool on the two different files with a unqiue field for APNCURRENT and APNPRIOR .  I'm working at putting it into a python script but new to Python. 

LIsa Pierce