Original data: 30 meter National Elevation Database GRID format (1999)
The Landform grid was created using Arc Macro Language (AML) in a two step process. Step 1: A Topographic Relative Moisture Index (TRMI) ArcInfo grid was generated using TRMIM.AML. Step 2: The Landform grid was created using LANDFORM.AML, which required the TRMI grid created in Step 1 and an elevation grid as inputs.
The 5-state region was initially divided into approximately 40 mapping zones. Landform grids were created for each mapping zone, which were then appended together forming a reional landform mosaic.
The following outlines the steps:
In ArcInfo grid: 1) Using TRMIM.AML (1-28 class) created the TRMIM grid for each mapping zone. 2) Clipped 1000 meters from the outer boundary of the TRMIM grid. 3) Merged TRMIM grids together for each state. 4) Using LANDFORM.AML created a Landform grid for each state. 5) Merged the state Landform grids together. 6) Converted 5-state grid to .img format.
Smoothing filters were applied in ERDAS Imagine:
In Imagine: 1) Ran 3x3 neighborhood majority filter across all 10 classes 2) Ran 5x5 neighborhood majority filter across classes 1 & 4 only 3) Ran 2nd 5x5 neighborhood majority filter across classes 1 & 4 only 4) Used CLUMP GIS function with 8 connected neighbors 5) Used ELIMINATE GIS function w/ minimum pixels to eliminate at 4 pixels (1 acre)
To remove irregularities that occurred in very large, flat areas such as the basins in Utah, Nevada and some parts of Arizona, these were screen digitized as an area of interest (.aoi) and recoded to "valley flats."
Notes: for more information see the TRMIM.AML & LANDFORM.AML for details on parameters used.
The 10 landform classes are:
1) valley flats 2) toe slopes, bottoms and swales 3) gently sloping ridges and hills 4) nearly level plateaus or terrace 5) very moist steep slopes 6) moderately moist steep slopes 7) moderately dry slopes 8) very dry steep slopes 9) cool aspect scarps, cliffs and canyons 10) hot aspect scarps, cliffs and canyon
For Citations see:
Parker, A. J. 1982. The topographic relative moisture index: An approach to soil-moisture assessment in mountain terrain. Physical Geography, 1982, 3,2, pp. 160-168.
Haplin, P. 1999. GIS analysis for conservation site design: A short-course developed for The Nature Conservancy. Nicholas School of the Environment - Landscape Ecology Laboratory, Duke University.
VALUE: Unique identifier required by the software
COUNT/HISTOGRAM: Number of cells/pixels for the landform class
RED: Required for display in Imagine
GREEN: Required for display in Imagine
BLUE: Required for display in Imagine
CLASS_NAMES: Landform class names.
The field CLASS_NAMES contains one of the following attributes: 1) valley flats (or water bodies) 2) toe slopes, bottoms and swales 3) gently sloping ridges and hills 4) nearly level plateaus or terrace 5) very moist steep slopes 6) moderately moist steep slopes 7) moderately dry slopes 8) very dry steep slopes 9) cool aspect scarps, cliffs and canyons 10) hot aspect scarps, cliffs and canyon
OPACITY: Required for display in Imagine.