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isiarkos

Problem during converting shapefile to feature objects

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Hello,

I have imported a shapefile containing multiple polygons (553 polygons). When i tried to convert the shapefile to feature objects (command "shapes to features objects"), GMS creates more than 553 polygons-features (about 5000! polygons-features). For example, a single polygon with a specific ID, when converted, is split into multiple features with the same ID.

How can this issue be addressed? It is important that during conversion to keep the same number of features as the initial number of polygons of the imported shapefile.  

Thank you in advance!

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1 hour ago, Michal said:

Hello, this is interesting. Maybe there are 553 multipart polygons in the shapefile and when converting to feature object GMS performs multipart -> singlepart conversion.

http://desktop.arcgis.com/en/arcmap/10.3/tools/data-management-toolbox/multipart-to-singlepart.htm

Your shapefile polygons may also be intersecting each other.  Check them in GIS first and correct topological errors.

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Thank you very much for your quick response!

Yes, that is exactly the case… The shapefile I imported contains multipart features. However, it is great of importance that these multipart features remain as multipart after conversion to feature objects (because they will be used as recharge zones).

Therefore, I would like to ask:

 a) Is there a command in GMS (i.e. something like “single part to multipart features”) that converts back the new split features into multipart?

 OR

 B) Is there a way to prevent GMS from splitting multipart to single part features during conversion (when executing the command “shapes to feature objects”)?

 OR

 c) Is there another solution in terms of maintaining multipart features during conversion to objects?

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Dear isiarkos

I would say you'd better include a "recharge code" field in your shapefile and use it to group polygons for recharge value assignment.  Or, you can assign recharge values to the shapefile so that recharge values will be transferred to feature objects when you process your shapefile in GMS.  This way, keeping multi-part features is not needed.

I hope this helps

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I agree with Hisham on this. There is no such concept as multipart polygon in GMS, as far as I know.

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Dear Hisham & Michal,

the procedure you mention, I think, refers only to steady-state models and we have already applied it in this type of simulation with no problem at all. In this case, we run a transient simulation so, as far as I know, we have to import the shapefile first (without the recharge information), convert the shapefile to feature objects and then assign the time-series with the recharge values to those features (using text import wizard and selecting "transient polygon data"). But the conversion procedure creates a large number of features, since we have multipart polygons, and the recharge value assignment does not properly done.

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Hi, try preparing the transient dataset so, that for each polygon in GMS coverage, there is a corresponding timeserie with the polygon id assigned at each row of the dataset. It will be a large dataset, but GMS should handle it unless you run out of memory.

Edited by Michal

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