[UW-GIS-L] watershed question

[Roy A. Justo]

I´ll try, thanks

2006/1/5, Todd Zackey <tzackey at tulaliptribes-nsn.gov>:
>
>  Ray,
>
> Have you tried using the Arc Hydro tools or data model?  You can get them
> at http://www.crwr.utexas.edu/archydrotools/tools.html.  One features of
> Arc Hydro allows you to have your pour points snapped to both your flow
> accumulation grid and your hydro arcs.  There is a lot of info about this on
> the ESRI website - Support - User Forums.
>
>
>
> -          Todd
>
>
>
> Todd Zackey
>
> Coastal Geographer
>
> Tulalip Tribes Natural Resources Dept.
>
> 7515 Totem Beach rd
>
> Marysville, WA 98271
>
>
>
> (360) 651-4805
>
> Fax # (360) 651-4490
>
> tzackey at tulaliptribes-nsn.gov
>
> http://www.tulalip.nsn.us/
>
>
>  ------------------------------
>
> *From:* uw-gis-l-bounces at mailman1.u.washington.edu [mailto:
> uw-gis-l-bounces at mailman1.u.washington.edu] *On Behalf Of *raytimm
> *Sent:* Thursday, January 05, 2006 12:23 PM
> *To:* 'UW - GIS Discussion & Support'
> *Subject:* [UW-GIS-L] watershed question
>
>
>
> Hi All,
>
> I have a problem that has been vexing me all morning and I'm sure
> (hopeful)  there is a simple solution.
>
> I'm trying to calculate "watershed" for a set of points that have been
> snapped to a stream network – all good so far.
>
> I failed several times to successfully calculate watersheds in both ArcGIS
> and ArcCatalog.  So I went back to the old standby, Workstation GRID – which
> requires that the source data are all in grids – still good so far.
>
>
>
> Here's my problem – or one of them:
>
> My pourpoint grid does not lie perfectly on my stream network grid even
> though my pour point coverage does lie exactly on my stream network coverage
> (they were snapped together originally).  When I look at my pout points,
> they look to be perfectly centered within stream network grid cells.  But,
> my pour point grid cells are apparently randomly incoherent with my stream
> network grid.  They may perfectly overlay, they may partially overlay, they
> may be adjacent but completely miss.  So, when I calculate watershed, my
> contributing upslope areas are not all associated with the stream grid cell
> locations.
>
>
>
> BTW, my stream network grid does lie at the intersection of flow direction
> patches.  So, that looks good.
>
>
>
> What I suspect is happening somewhere, somehow, is that there is some
> embedded geographic difference between the pourpoints and the stream network
> that isn't apparent because they were snapped together.  But, when I convert
> to a grid, the "true" location of the pour points is used.  Also, some of
> the pourpoints just seem to be missed in the calculation.  Is there a limit
> to the number of points you can use in this kind of calculation?  I don't
> get any weird errors – just weird results.
>
>
>
> Thanks for your help.
>
>
>
> Raymond Timm
>
> UW School of Aquatic and Fishery Sciences
>
> Box 355020
>
> 1122 NE Boat Street
> Seattle, WA 98195-5020
>
> 206-221-5403
>
> 206-685-7471 (fax)
>
>
>
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>
>
>


--
Roy A. Justo Torres
roydecadiz at gmail.com
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