topic Re: ASC to Polygon in ArcGIS Spatial Analyst Questions

ASC to Polygon

KevinTopping — Tue, 16 Nov 2010 09:39:32 GMT

Hi,

Desperate for some guidance on this. I am trying to convert ASC files to Polygons. I have a load of floating point ASC files, some brief details on them;

Columns/Rows: 2000/1000
Bands: 1
Cell Size 2.5/2.5
Format: AAIGrid

The ranges contain numbers to .10 decimal places and its very important I keep these to at least 3 decimal places in the final polygon (for symbology).

I was thinking that i need to use spatial analyst and convert to raster and then use the conversion raster to polygon tool. Can one of you please give some guidance on how i can do this and maintain the values.

Thanks in advance

Kev

Re: ASC to Polygon

DonovanCameron — Tue, 16 Nov 2010 14:57:36 GMT

You can use the ASCII to Raster tool and set data-type to Float.
You will also need to set the cell size, projection, workspace, and that can all be done in Environment Settings.

Then you can use GridShape, a map algebra statement to convert from raster to polygon. It supports floating integers.

Re: ASC to Polygon

KevinTopping — Thu, 18 Nov 2010 11:00:17 GMT

SaultDon,

Thanks for the reply, its appreciated.

I was under the impression if i converted to a floating point raster i could then not convert to polygon? I had been looking at doing a raster calculation but x the field by 10000 (which i then planned to divide by at the end?)

Kev

Re: ASC to Polygon

DonovanCameron — Thu, 18 Nov 2010 13:36:39 GMT

With the Gridshape function it will do the conversion on a cell by cell basis. I think this is most affected by what you have defined as the weeding parameter.

It's been a while since I ran this tool but I think it will also dissolve based on regions for the resulting polygon, and the values of the cell will then be stored in a [Gridcode] field.