Introduction

These web pages are part of a project to enable non-technical users to access and understand some of the data the MidCoast Watersheds Council (MCWC) has collected about salmonid habitat and juvenile presence. As a part of our work we have conducted snorkel surveys of salmonid juveniles in creeks throughout the midcoast and digitized the results into a GIS (Geographic Information System). The images presented on these pages are samples of data displays combining 3D terrain models with our salmonid juvenile survey data.

The salmonid juvenile presence, counts, and density data were collected for the MCWC during the summers of 1998-2001, though only the 1998-1999 data have been entered into our GIS. The protocol involves divers sampling every fifth pool along a stream and counting all salmonid juveniles in the pool, identifying them by species. In addition, they measure or estimate pool size and area, as well as distance between pools.

3D Modeling

The underlying terrain models were built by stitching together approximately 60 of the 10 meter (horizontal resolution) DEMs available from the Regional Ecosystem Office. I wrote a small AML to batch convert the DEMs from USGS format to ArcInfo grids, then used the mosaicall.aml script available from ESRI's ArcScripts to stitch them all together. From this very large grid, I was able to build a TIN for faster display of the data, though it only was useful for the air photo draped models. This is often referred to as a 2 1/2 dimensional model, because it does not truly capture vertical relationships.

The air photos seen on some of the images are Digital Ortho Quadrangles (DOQs) taken from the Oregon Geospatial Data Clearinghouse.

Actual modeling and display was done in the ArcScene component of ESRI's ArcGIS 8.1 3D analyst extension. Within ArcScene, I used the elevation grid or TIN to provide the base heights for all data, usually with a vertical exaggeration of 2 times and smooth areal shading on all features. After setting either the DOQs or the elevation grid (shown as the yellow-green shading in these images) as a base surface, I overlaid streams, watershed boundaries, and our rapid bioassessment data. To show coho density or counts, I set the extrusion for the pool features (a point shapefile) as appropriate so it would be easily viewed. The images on these web pages are from screen captures, as the extruded points do not show up well on exported (or printed) maps. Suggestions to remedy this are welcome!

GIS System

This model was built and manipulated with the following system:

Pentium 4 1.3ghz, 768MB RDRAM, GeForce2 MX400 video

ArcInfo 8.1 (particularly GRID module), ArcMap 8.1, 3D Analyst 8.1, and ArcScene