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Wondering if you I might get some advice on how to best create a polygon within a polygon based on an offset in ArcGIS. I have one layer that is a cadastral layer and another that is a building footprint layer (both polygons). The cadastral layer is plotted using coordinates but the building layer is based on offsets from the cadastral layer. What is the best way draw the building footprints in arcgis using an offset?

enter image description here

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    can you add an illustration of the problem? What do you mean by offsetting and having different shapes ? – radouxju Jan 3 '14 at 19:20
  • So I can plot the cadastral boundary using COGO but how do I plot the building footprint in side the boundary accurately. – rspencer38 Jan 6 '14 at 13:59
  • ArcGIS has a Copy Parallel command in the Editor Toolbar. – klewis Jan 6 '14 at 14:08
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There is a scale tool you can add to a toolbar and use. It's a command in the Editor Category.

If you have Spatial Analyst (and maybe VBA too if using 10x) you could try this Arcscript: http://arcscripts.esri.com/details.asp?dbid=15019.

If it won't run in 10x you could in effect do the same thing, which is use Spatial Analyst to convert to a raster, then use it's shrink tool, then convert back to a polygon.

Here is a script from an ESRI Forum on the same matter: http://forums.esri.com/Thread.asp?c=93&f=987&t=65352&mc=1#msgid168720, and another http://forums.esri.com/Thread.asp?c=93&f=987&t=220690

You could also try to create negative buffers. The problem with that is you may get errors/problems where that would produce no polygon.

  • If I understand it correct, these methods would be ideal for polygons within polygons that are of the exact same shape correct? If they were the same shape then scale/shrink would work. However, the building footprints and the cadastral layer are of different shapes so simply shrinking would not be useful. – rspencer38 Jan 3 '14 at 18:54
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    As radouxju suggested we need more information. If you have to use offsets that vary from line to line then I have no automated solution. Manually you could trace the cadastral line and set an offset distance for each section. Or you could convert your cadastral to lines and select and move individual lines using distances. Both could be a lot of work. – johns Jan 3 '14 at 19:43
  • I've posted an image of what I am trying to do. – rspencer38 Jan 6 '14 at 14:00
  • If you are getting your offsets from maps like that shown, and these are surveys/building designs, and you don't need absolute precision, I'd georeference the map to your cadastral layer, and then use the building footprint in the map to locate the building footprint cogo if you've made one, or draw one using the drawing and the distance option in the context menu when drawing a vertice. – johns Jan 6 '14 at 14:24
  • That certainly is an option but most of the surveys/designs come in via paper (and I hate it). Lots of manual scanning involved but it certainly is an option. – rspencer38 Jan 6 '14 at 15:04

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