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Posted by Jaume on April 7, 2008, 5:32 pm
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Hello,
I am a new user of ARCGIS doing research at my home university. I was
asked to llearn how to work with DEM for a project in which I am
involved, but I have no clue about how to use it. I have previous
experience with ARCVIEW, in which I did create a Digital Elevation
Model, but that was 3 years ago and I hardly remember how I did it. I
am supposed to create a shapefile of the hydrology of a place so this
is my question:
Which tool do I require to do that? (Extension)
How do I do that? Is there any tutorial where I could learn that?
I thank you for your help. I am sorry this questions might look
stupid.
Best Regards
Alberto Rodriguez Jaume
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Posted by Jean H on April 7, 2008, 5:43 pm
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Jaume wrote:
> Hello,
>
> I am a new user of ARCGIS doing research at my home university. I was
> asked to llearn how to work with DEM for a project in which I am
> involved, but I have no clue about how to use it. I have previous
> experience with ARCVIEW, in which I did create a Digital Elevation
> Model, but that was 3 years ago and I hardly remember how I did it. I
> am supposed to create a shapefile of the hydrology of a place so this
> is my question:
>
> Which tool do I require to do that? (Extension)
> How do I do that? Is there any tutorial where I could learn that?
>
> I thank you for your help. I am sorry this questions might look
> stupid.
>
> Best Regards
>
> Alberto Rodriguez Jaume
you need to provide more info...
-what data do you have?
-what do you want to do exactly?
-what have you tried?
Jean
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Posted by Jaume on April 14, 2008, 1:30 pm
Please log in for more thread options Well, this is what I have:
A group of 6 files with the same name but
with .tif, .rrd, .stk, .tfw, .xml, and .aux extensions. If I open it
in ARGGIS it shows a DEM of Dominican Republic. My intention is to use
a tool to find the rivers of the zone, the basins and sub-basins to
use it in my study. I tried to run directly hydrology tools (Flow
direction, basin, etc.). Some of them do process the informaiton and
produce other maps, but when I try to use "Stream order, stream link
and stream to feature" It asks for a stream raster... and I dont know
where to get it from. I use my original DEM but it gives me an error.
I looked online for other DEMs and found SRTM 90m Digital Elevation
Data from http://srtm.csi.cgiar.org/index.asp, but when I add it it
tells me that the raster data has no pyramids, if i choose to create
them, it says that "failed to build pyramids". and then that it cannot
be projected for some reason.
I want the same: to create a polygon layer of the basins and subbasins
and to create a vector file with the streams.
Thank you for your help :)
Alberto
wrote:
> Jaume wrote:
> > Hello,
>
> > I am a new user of ARCGIS doing research at my home university. I was
> > asked to llearn how to work with DEM for a project in which I am
> > involved, but I have no clue about how to use it. I have previous
> > experience with ARCVIEW, in which I did create a Digital Elevation
> > Model, but that was 3 years ago and I hardly remember how I did it. I
> > am supposed to create a shapefile of the hydrology of a place so this
> > is my question:
>
> > Which tool do I require to do that? (Extension)
> > How do I do that? Is there any tutorial where I could learn that?
>
> > I thank you for your help. I am sorry this questions might look
> > stupid.
>
> > Best Regards
>
> > Alberto Rodriguez Jaume
>
> you need to provide more info...
> -what data do you have?
> -what do you want to do exactly?
> -what have you tried?
>
> Jean
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Posted by Jean H on April 14, 2008, 4:45 pm
Please log in for more thread options Jaume wrote:
> Well, this is what I have:
>
> A group of 6 files with the same name but
> with .tif, .rrd, .stk, .tfw, .xml, and .aux extensions. If I open it
> in ARGGIS it shows a DEM of Dominican Republic. My intention is to use
> a tool to find the rivers of the zone, the basins and sub-basins to
> use it in my study. I tried to run directly hydrology tools (Flow
> direction, basin, etc.). Some of them do process the informaiton and
> produce other maps, but when I try to use "Stream order, stream link
> and stream to feature" It asks for a stream raster... and I dont know
> where to get it from. I use my original DEM but it gives me an error.
This raster should contain only no-data or 1, where it is a stream.
from the help file:
------------------
The results of Flow Accumulation can be used to create a stream network
by applying a threshold value to select cells with a high accumulated
flow. For example, the procedure to create a raster where the value 1
represents the stream network on a background of NoData could use one of
the following:
Perform a Con operation, where the input conditional raster is
"Flowacc", the input true raster a constant "1", and the expression ">
100".
Alternatively, perform a Set Null where the input conditional raster is
"Flowacc", the input true raster a constant "1", and the expression "<
100".
In both examples, all cells that have more than 100 cells flowing into
them are assigned 1; all other cells are assigned NoData. For future
processing, it is important that the stream network, a set of raster
linear features, be represented as values on a background of NoData.
The resulting stream network can be used as input to the Stream Order,
Stream Line, and Stream Link.
This method of deriving accumulated flow from a DEM is presented in
Jenson and Domingue (1988). An analytical method for determining an
appropriate threshold value for stream network delineation is presented
in Tarboton et al. (1991).
------------------
You have to correct the DEM first though... if you have sink holes in
the DEM, water will not flow and you will not see the rivers using this
method!
then all other tools **should** work well...
Jean
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Posted by Jaume on April 16, 2008, 1:19 pm
Please log in for more thread options Thank you very much for your help. Now another question, I ran the
Sink tool and got a raster. Now, do I run the FILL tool with this
raster or with the original raster?
Thank you very much!
Alberto
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