Analysis of the Little Pecan Lake Wetland Management Plan in MOSS 



MOSS was designed to allow users to enter, retrieve, analyze, and display maps and other spatial 

 data stored in the system. MOSS uses two data formats: vector and cellular. CMD uses MOSS 

 primarily for its vector capabilities; however, a subsystem, the Map Analysis Package (MAPS), can 

 be used to manipulate cellular data. The following MOSS products were created for the example 

 area: 



a. VICINITY MAP - A vicinity map was created to allow the reader to be familiar with the study 

 area (Figure 1). 



b. STUDY AREA MAP - A study area map was created based on the marsh management plan 

 boundaries (Figure 2). 



c. OVERLAYS - The management area polygon can be overlaid with the 1956 and 1978 habitat 

 maps (Figures 3 and 4). 



The management area can be overlaid with the permit data (Figure 5). 



In addition, the management area can be overlaid with the Louisiana National Heritage Program 

 (LNHP) data (Figure 6). 



d. SPECIFIC HABITAT INQUIRIES - Any habitat type can be singled out for analysis. In 

 this instance we are interested in total water area for 1956 and 1978. Figures 7 and 8 

 represent the 1956 and 1978 water maps for the management area. 



Habitat review could be done for the canals present in 1956 and 1978 (Figures 9 and 10). 



Erdas Analysis of the Little Pecan Lake Wetland Management Plan 



CMD uses ERDAS to obtain habitat change statistics for individual wetland management plans 

 within its coastal data base. MAPS (MOSS cellular format) can also be used to obtain habitat 

 change data for plans but is not as efficient or as user friendly as ERDAS. In addition to 

 providing change statistics, ERDAS is also used for specialized analysis procedures such as the 

 compilation of land loss density maps, and land and water interface complexity maps. 



Analysis of the Little Pecan Lake wetland management plan in ERDAS first requires that the 

 1956 and 1978 habitat plan overlays be converted from a vector format to a cellular format. The 

 cell size used was 10 m 2 . As stated previously, MOSS is a vector-based GIS. A vectory system 

 identifies each polygon as a unique area. For example, individual marsh ponds on the digital 

 habitat maps are represented as separate polygons in MOSS. The ponds may be of the same 

 type but will have different areas. ERDAS, a cell-based system, will divide a map into a series 

 of 10-m 2 cells, each the same size as its neighbor. In this case, a specific value will be assigned 

 to all cells in the map representing freshwater ponds. The advantage in using cell maps is that 

 change statistics are much easier and faster to obtain. The main disadvantage is that maps 

 produced using a cell format are not as appealing to the eye as those produced using a vector 

 format. Area figures for the cell maps may differ from those produced by vector maps but the 

 difference is negligible. After conversion to a cell format was completed, the plan habitat overlays 

 were changed to an ERDAS-readable format for analysis. 



Development of the Habitat Change Maps. The first step in the land loss analysis of the 

 management plan was to simplify the original wetland classifications to a land cover classification 

 system consisting of 16 habitat categories using the RECODE program in ERDAS. The simplified 



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