397
USER ALTERNATIVES IN POST-PROCESSING
FOR RASTER-TO-VECTOR CONVERSION 1/2
Thomas L. Logan
Jet Propulsion Laboratory, California Institute of Technology
4800 Oak Grove Drive, Pasadena, California 91109
Curtis E. Woodcock^
Department of Geography, University of California
Santa Barbara, California 93106
ABSTRACT
A number of Landsat-based coniferous forest stratum maps have been
created of the Eldorado National Forest in California. These maps were
produced in raster image format which is not directly usable by theU.S.
Forest Service's vector-based Wildland Resource Information System
(WRIS). As a solution, raster-to-vector conversion software has been
developed for processing classified images into polygonal data struc
tures. Before conversion, however, the digital classification images
must be simplified to remove high spatial variance ("noise", "speckle"),
and meet a USFS ten acre minimum requirement. A post-processing
(simplification) stragegy different from those commonly used in raster
image processing may be desired for preparing maps for conversion to
vector format, because simplification routines typically permit diagonal
connections in the process of reclassifying pixels and forming new
polygons. Diagonal connections are often undesirable when converting
to vector format because they permit polygons to effectively cross over
each other and occupy a corrmon location. Three alternative methodol
ogies are discussed for simplifying raster data for conversion to vector
format.
INTRODUCTION
For the past three years, the University of California at Santa Barbara
and the Jet Propulsion Laboratory in Pasadena, California, have been
developing a Forest Classification and Inventory System ('FOCIS';
Strahler, et al., 1981; Strahler, 1981). FOCIS is designed for large
area western North American coniferous forest inventory, and uses a
digital terrain model and registered Land sat data. The FOCIS procedures
were first tested in the Klamath National Forest located in northern
California, and were found to produce inventory estimates of similar
quality as those produced by conventional techniques. However, FOCIS
was found to produce more timely and cost effective inventories.
Currently, FOCIS procedures are being applied to the Eldorado National
Forest on the west slope of California's Sierra Nevada Mountains. One
^Presented at Auto Carto 5/ISPRS IV, August 22-28, 1982, Crystal City,
VA., USA.
7
This paper represents one phase of research conducted at the Jet
Propulsion Laboratory, California Institute of Technology, under
NASA contract NAS7-100.
■^Now with the Department of Geography, Hunter College, City of New
York University.
