Developing the RHESSys / ArcView Integrated Modeling Environment

David Tenenbaum

Univ. of North Carolina-Chapel Hill

Landscape Representation

RHESSys divides the landscape into a series of successively contained partitions

World

Basin

Hillslope

Zone

Patch

Stratum

1) The method for creating a partition is determined by the processes it will represent

2)

Once landscape objects in a partition are defined, parameters at that level can be calculated

3)

Old technology: grass2world

• GRASS - a shareware raster GIS produced by the U.S. Army CERL

• Augmented with standalone code for unimplemented functions and algorithms

• Methods and results stored in ASCII text files

Visualization of results and comparison of methods is AWKWARD

New Technology: RAIMEnt

R HESSysA rcViewI ntegratedM odelingE nvironmentnt

•implemented in ESRI’s ArcView GIS using Avenue

•Presents tightly coupled functions accessed using a single graphical user interface (GUI)

•Methods and results stored in Shapefiles and tables Visualization of results

and comparison of methods is EASY

RAIMEnt Partitioning

• Specify a theme for partitioning using a dialog box

• Performs a raster intersection with its parent partition

• New partition is produced and shown

• Method of partitioning is stored in Partitioned Objects Table

RAIMEnt Parameter Generation

• Specify methods using a short string, stored in Parameter Generation Table

• Methods include:– constant– equation– expression using

spatial data• Results are calculated,

method stored in table

The key advantages• ArcView Shapefile / Theme

representation links parameters to the spatial representation of objects for easy visualization

• Model runs managed and output visualized on the fly

• Optimal capabilities of raster and vector data models are used

• Storing partitioning and parameter generation methods inside RAIMEnt along with results promotes the learning of effective new methods

What RAIMEnt offers here

RAIMEnt offers an environment where augmenting RHESSys can be explored efficiently and effectively, so that we can more quickly learn new methods for the effective representation of landscapes, and accumulate this knowledge by storing the methods systematically along with their results

Development Issues

RAIMEnt as a prototype for a system for supporting RHESSys revealed some of the significant difficulties in doing so:

•RHESSys evolves quickly ... Parameters and even its structure changes

•File sizes and processing time can be large enough that the GUI is not pleasant to use

•Trying to house all the required functionality in one package is tricky

Development Solutions

RAIMEnt as a prototype has evolved to deal with some of these problems:

•System reads the object structure from a table, which can be modified to reflect changes

•‘Tricks’ in coding can make handling the large World more efficient

•Expanded capabilities through linking with external executables (another ‘trick’).

Where To Go From Here

The key issue in developing a support system for RHESSys is how complicated / capable it should be:

•grass2world is very simple and easy to use but places a significant burden on the user to know a lot about RHESSys in creating a useful World

•RAIMEnt is too complex and difficult to use / make work, and tries to take on a lot of that burden, perhaps too much

From Prototype to Release

•There is a middle ground between grass2world and what I tried to do with RAIMEnt

•By developing and enhancing this prototype I have a clearer idea of how to write a package that will be useful and easy to use

•There is a real demand for me to get this done ... but I still need to ask for your patience ... in a half-baked form, I don’t think this software is going to help anyone use RHESSys