THREE-DIMENSIONAL MAPPING APPLICATIONS AT THE DELAWARE GEOLOGICAL SURVEY

Until recently the Delaware Geological Survey (DGS) exclusively used 2-D mapping software to research, map, and render tops, bottoms, volumes, and hydraulic attributes of multiple aquifers. Quasi three-dimensional analysis of aquifer properties is accomplished by vertically integrating over layers of arbitrary constant thickness or layers of variable thickness with prescribed stratigraphic boundaries. Grids of aquifer tops and bottoms are also used to determine which aquifers are used by individual water wells and to automate the assignment of wells to aquifers.

Because DGS is a small organization without appropriate programming skills on staff, the decision to map in 2-D was largely based on the lack of 3-D mapping capabilities in affordable and commercially available software. Software being used include ArcMap with the Spatial Analyst, Geostatistical Analyst, and 3-D Analyst extensions, and Golden Software's Surfer.

Available 2-D grids produced by the DGS are county-wide and have 30 m horizontal resolution. Grids range in size from 1.5 to 4 million cells. Typical input point datasets range from 300 points for deeper aquifers to 5000 points for the unconfined aquifer. DGS is now in the process of researching the capabilities of a newly released software title (Golden Software Voxler) to generate 3-D lattices and render 3-D volumes. Because of the limited capabilities of this version, we are experimenting with conversion of 2-D grids of tops and bottoms into 3-D volumes as well as computing the 3-D lattices from point data sets.