Merging multiple polygons

[Land337]

I am dealing with a land parcel that is split into multiple polygons due to roads transversing the property. When exporting the shapefile, multiple attributes appear in the dbf which throws off my acreage counts. Anyway to merge these polygons in order for the shapefile to read as one attribute? 

Thanks!

[Pointdump]

Hi Ryan,
How about a separate shapefile for the "big picture"? Like when you get shapefiles of a country.

_adm0.shp (shapefile of whole country)
_adm1.shp (shapefile of states)
_adm2.shp (shapefile of counties)

Dave

[Land337]

Hi Dave,

I don’t think this will work since each parcel is joined with an excel document to populate the attribute table. 

Example: Tract 1 is 640 acres split up into 4 separate polygons. The spreadsheet I am joining my shapefile with only has 1 row of data and list Tract 1 as 640 acres. When I export my shapefile after the join, I am left with 4 rows totaling an acreage of 2,560 in lieu of 640. 

[parkr4st]

what are the data types?

starting with cad drawing objects or a .shp?

what file type is the shape exported to? 

a .shp can be exported to a .sdf file.   was this done?

how will the polygons be joined? in what file type?

if polygons are joined using mapfeaturemerge the areas will be summed in the data table

why is an excel file involved? & how?

[Land337]

Thanks for your reply!

The data comes from the county assessor via shapefile which is then joined with a spreadsheet to populate the clients data/information (Tract numbers, Status, etc). This shapefile is updated weekly by joining my shapefile with an updated spreadsheet from the client to obtain status changes. When the engineer is running an analysis in ArcMap, these split tracts are doubling the acreage figure. I need one row per tract when my AutoCad tracts are exported.

I have attached a sample shapefile to help assist!

[parkr4st]

with the data, opened Tracts, saved to SDF file

Put that SDF into a new map and added calculation Acres   Area2d(Geometry)/43560  The acres do not agree with the Assessed_A field.  What is right?

saved to SDF and put that SDF into a map

selected pairs across the road and MAPFEATUREMERGE for each pair and checked in all.  The result is acres are added for each pair with 5 records.  

Somewhere near to what is wanted?

[ChicagoLooper]

Hi @Land337 

Based on the parcel data you uploaded, you have exactly 10 parcels, 5 western parcels and 5 eastern parcels with Old River Road dividing the west from the the east. Do you want to combine the acreage of for each TRACT? I ask, because you didn't clearly explain exactly what you want to achieve.

Don't make the mistake of describing the workflow you think will work or a workflow you've already tried because it may not be a practical way to get what you want. Describe, as clearly as possible (the more details the better) your end goal, then let the forum figure out how to get there. 

If you simply want to combine AREA, then a possible workflow would be: 

1. Calculate or determine the area for each individual parcel.
2. Identify the Tract Number. 
3. Add (combine) the the Area for for parcels that have the same Tract number.

I wouldn't MERGE the parcels. Keep them separate. If you merge, you may lose data. You don't want to lose or overwrite data, you want to MANAGE the data, and if needed, create new data, which in your case would be Total Area per Tract.

[Land337]

Thanks for the reply!

I will explain what I am trying to accomplish:

I have have a shapefile with a unique identifier (Tract No.) that I join with an excel spreadsheet weekly for tract status updates. I then connect to the new shapefile and style the map to achieve the information the client is looking for. The joined shapefile is then sent to the client for there database update. When the client runs the acreage figures in ArcMap, the tract acreage figures are incorrect due to each polygon (making up one tract) having the total tract acreage. This acreage figure is being pulled from the spreadsheet in join with so it isn't a calculated area from the shape....

Example

Tract 0013 is made up of two polygons, split by a road. Each attribute has the total acreage of the entire tract that was obtained from the spreadsheet join. I need Tract 0013 to only register as one row in the data table and carry over when a new shapefile is created.

Keep in mind, over 1000 tracts are associated with this project and are updated weekly. Not all are multi-polygon tract but 20% are. Do you have any tips, tricks or solutions?

Thanks!

[O_Eckmann]

Hi @Land337 ,

When you've selected the 2 portions of parcels, you can merge into 1 multi polygon feature

So you have only 1 objet with 2 geometry.

Be carefull when merging polygon, you have to declare rules for merging / splitting to avoid calculation on real fields.

When merging, chose first or last selected to avoid sum of area

When splitting, you can choose to divide according proportion of area

Sorry for french terms

Olivier

[parkr4st]

1st question:  Why does the client treat one parcel as two?  if each parcel has subparcels change the identifier to 1-A & 1-B and correct the area; or combine the parcels, correct the area, and tell the client to stop #$%^& with the data.

someone needs to be in charge of the data. period.

2nd question: Does the excel update only bring in data for parcels where the data was changed or all of the parcels?

3rd question: why does a client with arcmap need you to do what you do?  

4th question: why do you need the client to do what they do?

           would seem simpler if only one party changed data and produced results. either software can do all that you describe IMHO. a jpg graphic from you would explain the data and no one else could mess with the data.

This whole process appears IMHO to need a very regimented process so that the data does not get #$#%$^&^ up which seems to be the real problem.

[parkr4st]

And make sure your errors and ommissions insurance is up to snuff.  it will probably be needed if the data is not brought under control 🙂 

[ChicagoLooper]

Hi @Land337 

There are too many variables when running a JOIN. Would it be possible to share your shapefile AND your spreadsheet?

In addition to sharing your files, it would also help to view your settings when you performed your JOIN. Can you upload an image of the dialog box when you created your Join?