Construction of the Geographic Information System (GIS)

Overview

A major product of the initial methodology assessment is a GIS base map supporting the reconnaissance/planning activities. This tool is intended to support analyses that will yield three representative “railroad realignment corridors”.

The mapping categories will support examination of the corridors according to the principal evaluation criteria, which include:

1. Minimal disturbance/minimal impact on plant and animal communities “of concern”
2. Minimal disturbance/minimal impact on cultural/historical sites “of concern”
3. Minimal disturbance/minimal impact on existing human populations
4. Optimal cost control in terms of construction, right-of-way acquisition and areas “of concern”

The construction of the GIS base-map involved the following steps:

1. Basic data collection and integration
2. Design and operation of analytical processes to enable identification of probable/possible areas of concern to cultural and biological experts and that supply basic topographic information to the project transportation engineers

The general components of the GIS base-map are:

1. Comprehensive landscape view
2. Basic transportation infrastructure- existing roads and railroads
3. Basic hydrology- streams, rivers, water bodies
4. General terrain model- elevations
5. Soil characteristics relating to wetlands and “wetland indicator” plant communities
6. Cultural/population features: point locations of cities and towns, point locations of archaeological significance
7. Areas of special significance to the project- boundaries of national forests, wildlife management areas and wildlife preserves

Data Sources

1. SPOT Satellite imagery. A series of SPOT data scenes was acquired for the project. The scenes are cloud free acquisitions made between 1999 and the present and offer a current view of the six-county region. The data can be used to interpret general landscape features, such as forested areas, areas of shrub/scrub, clear cuts and farmed areas, areas of population, roads, infrastructure, streams and water bodies.
2. U.S. Census Bureau TIGER 2002 files were used to develop maps of transportation features and basic hydrology.
3. USGS Digital Elevation Model (DEM) data were acquired to develop a basic overview of terrain elevation.
4. USDA NCRS SSURGO data were acquired to develop the highest possible resolution map of soil types.
5. Point observations of “Environmentally Sensitive” and “Archaeological Significance” were acquired from State of Mississippi spatial data collections (MARIS) and from team consultants (Earth Search Incorporated).
6. Boundaries of Concern. Data regarding the boundaries of Wildlife Management Areas, National Wildlife Reserves and National Forests were acquired from State of Mississippispatial data collections (MARIS) . The design of the rail realignment corridors would attempt to avoid, where possible, intersection with “boundaries of concern.”

The information available on the base maps can be displayed in a number of combinations to form patterns that reveal the geographic extent of the specific characteristics of the project area.