Steve Hartley, Jimmy Johnston, and Pat O'Neil, USGS/BRD/NWRC

Louisiana GAP Analysis Project: Usage of Auxiliary Data Sets

Good ancillary data sets are rare. Fortunately, Louisiana is blessed with an abundance of high quality auxiliary data sets. The most important of these data sets is the 1988 National Wetlands Inventory (NWI) data, which covers approximately one-third of the southern half of the state. The Louisiana GAP Analysis Project is using this data in conjunction with Thematic Mapper (TM) imagery to produce a vegetation map of the state. The merging of these two data sets, however is not a simple process. One must consider the origin and format of the two different data sets. One data set is vector (NWI) and produced by photointerpretation of aerial photography and the other is raster (TM) from satellite imagery. In order to merge the two data sets, the NWI Cowardin classification scheme has to be reclassified to the Louisiana GAP classification scheme and converted from vector to a raster data format. This procedure allows the two different data sets to be merged into one, however it does not take into account the spatial resolution of the two different data sets or the temporal changes between the sets. Temporal changes are limited to change in upland forest evergreen and mixed categories along the merge line between the two different data sets. In order to accommodate these differences we have had to create a subset of the NWI upland forest evergreen and mixed categories and integrate TM imagery for further processing. The final product is a merged file of classified NWI and TM data sets.

Louisiana GAP Small Sample Data

Other auxiliary data sets used in the Louisiana GAP vegetation classification include 1995 color-infrared photography (CIR), SPOT data, and ground truthing data. These data sets significantly help to classify the TM imagery.

Steve Hartley, Jimmy Johnston and Pat O'Neil
United States Geological Survey, National Wetlands Research Center
700 Cajundome Blvd.
Lafayette, LA 70506
Telephone:(318)266-8543
Fax:(318)266-8616
e-mail: hartleys@nwrc.gov