Roland Viger: Hello my name is Roland Viger.
I’m with the Modeling of Watershed Systems Project and I’m going to talk to you briefly
about the GIS Weasel.
Which is a preprocessor, largely, for deriving maps of features and parameters for use with
PRMS or really a number of other kinds of models, watershed models.
This presentation is meant to be viewed in conjunction with a separate recording which
actually shows a demonstration of the GIS Weasel software.
Here is the homepage to get the software.
It’s been around for really over 15 years by now so it’s pretty mature.
There’s a big document describing not only how to use it, but there is an appendix which
helps you understand how parameters are derived and especially if you want to use the GIS
Weasel to set up models other than PRMS, it’s pretty helpful to see the exact methodology
and decide whether those techniques are actually appropriate for that other model.
Because this is a long standing piece of software, the technology on which it is built is now
a little bit dated.
It’s still fully functional, totally accurate and useful, but it relies on Workstation ArcInfo
and it uses the Grid raster processing software module underneath Workstation.
So, when I say “Workstation”, I put a little screen grab, this is pretty simple,
but I really want users to see this.
If they don’t have the ability to call up this kind of window on their computer, then
they probably don’t have Workstation ArcInfo.
When I say ArcInfo or ArcGIS, I’m not referring to Desktop, which is the newer, more modern
incarnation of what we think of with ArcGIS.
This software is great, but it is not what the GIS Weasel is built on top of.
So you need to have that Workstation software.
The good news is that if you do have a desktop license, and that software running on your
computer, you’ve actually purchased the license for the Workstation software.
Some system administrators are just choosing not to install the Workstation software, but
they can get it, they’ve paid for it, they are allowed to have it and they are allowed
to install it.
That shouldn’t be too big a deal.
So, for what it’s worth, ArcInfo is up to 10.2, soon to be 10.3, in terms of the version
number and Workstation was frozen at 9.3 and that works just fine and that’s what we
use across the U.S. Geological Survey.
We don’t provide support on how to set all of that up.
You just need to talk to your own system administrators, or if you do your own administration, then
you need to take care of that.
Again, we’re built on top of Workstation and it uses the Arc Marco Language which is
the scripting language for that platform and it’s pretty much self-contained.
It doesn’t require anything like registry edits on windows or compiling or anything
like that.
You just download it and open it up.
There is some installation instructions on the web site which help you tweak the properties
for the short cut that makes it even easier to start that software.
Please read those in case you get any hiccups during the install process.
Other requirements are a digital elevation model, it’s a pretty lightweight requirements.
This is because it is ArcInfo Workstation you need it to be in a grid format, so it
cannot use some of the more modern ones, such as Geotiff.
It is strongly recommended that you project your digital elevation model into something
like an equal area projection.
So don’t use lat/long as your coordinate system and even an equal angle projection
is not recommended.
Mostly because when you do things like calculate the areas of your features like a hydrologic
response unit you want a projection that will give you accurate numbers.
That’s really the only required input data set.
During the setup part of the GIS Weasel, you will be asked to define the basin or area
of interest and you can have a preexisting outline, in fact, we almost discourage that.
You’re really recommended to just be able to define the outlet point and let the software
find the contributing area based on analysis of the DEM.
Another requirement is the Data Bin.
In terms of delineation of your features, by and large, most folks rely on the digital
elevation model almost exclusively.
Not a requirement, if you want to delineate on the basis of some other ancillary data,
then you need to show up with those data available.
And, again, those should be in an ArcInfo grid format and they should be in the same
coordinate system as the digital elevation model.
By and large, the Data Bin could be used for this, but the Data Bin is specifically engineered
for helping to derive a standard set of parameters, specifically oriented towards the PRMS watershed
model.
So, these are the kinds of layer that we have in the Data Bin.
We’ll show you a little bit later on a schematic of what that should look like.
If you can’t quite get everything you need off of the screen grab in this powerpoint,
it’s definitely straight from the GIS Weasel users’ manual.
So you can go back and refer to that.
Another key, if you need to build your own Data Bin is that when you download the GIS
Weasel, there is a Data Bin in there and this is just for a little sample watershed, but
you can look at the structure and naming conventions of all the contents in there and just mimic
that in terms of recreating your own Data Bin.
This is the general structure where you’ve got ArcInfo workspaces, essentially directories
in red.
You’ve got your ArcInfo grids in the blue boxes and then the yellow tables are the info
tables inside of that workspace.
You see the code schemes associated with the grids in these different layers.
So, more detail on this is provided in the GIS Weasel users’ manual and you can look
there for definitions.