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| GeoCommunity Mailing List |
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| Subject: | RE: [gislist] Working with raster data |
| Date: |
09/23/2003 02:30:02 PM |
| From: |
David Crosby |
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If you have Spatial Analyst or GRID, you could use the zone functions - assuming that your slope
grid has been relcassed to a binary grid - 1's for > 40 and "no data" for everything else, you could
SUM the number of grid cells using your tree stand polygons as a zone.
To calculate the overall area for for your study area where slope is > 40, simply take a look at
your GRID statistics - this will be in the attribute table. Take the number of grid cells with a
"1", and multiply that by the area of each grid cell. So if you have 6000 cells with a "1" denoting
the > 40 slope, and you are using a 25m cell size, this would be 625 metres squared x 6000 = 3750000
square metres.
Dave
>>> "Bill Medina" <wmedina@kci.com> 9/23/2003 1:22:59 PM >>>
I would suggest that you convert the DEM to a shape and intersect the two
polygon files you will have all tree polygon in the areas with slope greater
than 40% then get the areas calculated (see help to see how to do it) and
summarize areas based on the polygons with slopes greater than 40% from the
polygon file or get the count number of cell from the raster and multiply it
by the area of each cell.
Hope it works,
Bill M,
-----Original Message-----
From: gislist-bounces@lists.thinkburst.com
[mailto:gislist-bounces@lists.thinkburst.com]On Behalf Of Neil Havermale
Sent: Monday, September 22, 2003 7:16 PM
To: 'michele@wildapache.net': 'gislist@lists.thinkburst.com'
Subject: RE: [gislist] Working with raster data
You would need to intersect the slope polygon of 40%=> DEM with tree stand
polygons essentially. I am not ArcGIS skilled so I apologize for the lack of
a detailed step-by=step. If you are interested in learning some of the
conceptual issues related to your topic you might take a look at some of the
case examples at:
http://www.innovativegis.com/basis/Senarios/Default.html
MidNight Mapper
Aka neil
-----Original Message-----
From: Michele Mattix [mailto:michele@wildapache.net]
Sent: Tuesday, September 23, 2003 8:46 AM
To: gislist@lists.thinkburst.com
Subject: [gislist] Working with raster data
Greetings everyone --
I am new to desktop ArcGIS and am having a challenge with a project I'm
working on. I have a polygon file with tree stand types identified. I also
have raster DEM data which I used to calculate slope. Slopes that are
>40% get a "1" and they are displayed on my map. I need to calculate
>the
(partial) area of each tree stand polygon which has a slope > 40%. I will
also need to calculate the overall area for the entire study area where
slope > 40% How do I do this with raster data?
Thank you for your help.
Michele
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