Divide Polygon in equal areas

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02-14-2012 05:06 AM
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New Contributor II
Dear community,

we are working with a lot of big forest parcels and want to divide them into (exact) 1ha, 0,25ha parcels and so forth. Is there any kind of algorithm which could do this automatically? Up to now, we are overlaying polygon-rasters of smaller size then the desired output and merge the small squares. But of course the parcels we get cant fit 100% in our forest area (squares in irregular polygons). Other solutions are drawing parcels by hand and estimating the area, calculating it as an attribute, take a small bit of or ad a bit and so forth until we get the area of 1 Hectar.

Do you guys have any idea how we can automate this process? and if not as "divide polygon in 0,25 ha pieces" something like " divide polygon in 20 equal areas"? It would save us time and space in our layers :rolleyes:

I fear this is to heavy to calculate but still hope for suggestions

thanks for you input, regards Konrad
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Regular Contributor III
Hey Konrad,

If I got you right, you might like the Create Fishnet tool: http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00170000002q000000

You can choose to create a specified number of rows and columns or specify cell's height and width. Then you specify the extent of your original forest polygon which will limit the output feature class. Do you need to perform any attribute transfer afterwards (i.e., all the attribute a big forest area feature has should be transferred to the output of the tool)?

Let me know if this method works for you.
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New Contributor II
Dear Alexey,

thanks for your answer. The fishnet solution is exactly how we are working at the moment. But since the result is a bunch of SQUARES, it usually doesn't fit our IRREGULAR forest polygon 100%. As we are talking of hundreds of parcels we have to work with automatic processes. So I populate a fishnet with the desired area (or smaller and merge them afterwards). Then I clip the fishnet polygons with the forest polygon and delete all parcels which are smaller then the given fishnet area (since they have been clipped). Therefore unfortunately, after cutting all squares which are not exactly 0,25 ha (for example) I have a lot of area which is then classified as not used (see attachment).

Thats why I was asking for a solution which would divide THE WHOLE area in subpolygons, even if they are irregular in their shape. Meaning I would tell Arcgis to divide my forestpolygon of 31,7h ha in 31 parcels (meaning each of them a bit bigger then 1 ha). That would be exactly what we are looking for to avoid gaps at the edges (which can easy add up to some hectares in our case).

I hope I could explain it somehow clear, sorry for my bad written english ...
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Regular Contributor III
Hi Konrad,

I see now. Hm, I believe the only way to do this type of work in an automated fashion in ArcGIS 10 would be using Parcel Fabrics. Check this page to get a general idea what you can do: http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//001t000003wp000000.htm. If it is something you want to give a try, I suggest going through tutorial for parcel editing.

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Tutorial_Getting_started_with_parcel_f...

The tutorial data is included with ArcTutor which you can obtain when having an ArcGIS Desktop license (contact your distributor if you don't have it). Take your time to learn parcel editing since it is quite large amount of tools and settings there.

If I read things right (have not worked with parcel editing a lot either), then this is the type of task you should look into: http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Creating_new_parcels_using_divide_by_a...

Let me know when you got your hands at parcel editing and if it went well to divide your large forest area as you need.
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New Contributor II
Wow! Thanks a lot, thats 100% what we need. Unfortunately, we only have an ArcView License and to upgrade for the Parcels Editor only seems not feasible. I will investigate in all OpenSource solutions and also the free Script which exists for ArcView 3.0 on the ESRI sites.

http://forums.esri.com/Thread.asp?c=3&f=38&t=208496

Thanks again for your helping me with this ...
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New Contributor II
sounds weard, but there seems to be absolutely NO solution for this basic problem (apart from the Parcels Editor). I found a commercial extension being able to split a Polygon ONCE. Not feasible though to divide a whole area.
http://www.ian-ko.com/ET_GeoTools/UserGuide/ETSplitPolygonByArea.htm

Any further input will be highly aprreciated guys. Thanks in advance !
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New Contributor III
Hi Konrad,
  What version of ArcMap are you using. Based on other forum posts you have made, I am assuming you are using ArcMap 10.0 with an ArcView license. You did, however, say that you were looking for scripts for ArcView 3.0.  If you could confirm your version, this would help me in assisting you.


Regards,

Juliana W.

ESRI Desktop Support
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New Contributor II
I'm Looking for the same solution. I have irregular Polygons and want to divide into 2 polygons with equal area.

I have ArcGIS 10 and Spatial Analysis. Please advise how I can do this.

Paul
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New Contributor III
Hello,
As Alexey already mentioned, Parcel Editor is probably the best way for you to do this.  Parcel Editor is included in the  ArcEditor and ArcInfo license level. 
You can find out more by reading the page �??About dividing parcels by area in the parcel fabric�?� at http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//001t000003wp000000.htm.


Regards,

Juliana
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New Contributor II
Hi Konrad,
  What version of ArcMap are you using. Based on other forum posts you have made, I am assuming you are using ArcMap 10.0 with an ArcView license. You did, however, say that you were looking for scripts for ArcView 3.0.  If you could confirm your version, this would help me in assisting you.


Regards,

Juliana W.

ESRI Desktop Support


Juliana, sorry for the confusion and thanks for your help. We have indeed an ArcMap 10.0 with an ArcView license only. I found some scripts from Bill Huber (who seems to be the only guy in the whole world wide web who has a real clue about the issue 😄 ) which only work in ArView 3.3 thats why I did some research there as well. But since ArcMap cannot import scripts, its useless.

So I am here, right at the beginning of the story again. Not knowing what to do. I found a PostGIS script which can divide a Polygon in two exact half pieces, but for me thats not enough.

It would be so great if Esri would sell single Toolboxes. We are only interested in this little function, or lets say the parcel Manager. Not the whole Editor or even Info License .... 😞
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