PAMAP LIDAR-BASED ELEVATION DATA: A NEW TOOL FOR GEOLOGIC AND HAZARD MAPPING IN PENNSYLVANIA

The PAMAP program is collecting statewide high-resolution LiDAR elevation data. Standard products derived from the classified LiDAR data are 3.2-foot gridded Digital Elevation Models (DEMs) and 2-foot contours. The data were collected to meet FEMA Map Modernization standards, and will be used to support new flood hazard maps. LiDAR data for approximately one-third of Pennsylvania were gathered in 2006, and a second third of the state was flown in 2007. Preliminary data from the 2006 flights is available now to researchers, and the final version will available to the public after Quality Control is completed in early 2008. Use of the high-resolution elevation data greatly enhances visualization of map data, and it is probable that many standard map products will begin to incorporate hillshades and other 3-D visualization as regular features.

The initial data show great promise to enhance mapping of both bedrock and surficial geologic features. LiDAR coverage of Luzerne County, in northeastern Pennsylvania was obtained as a pilot project. Remarkable delineation of large bedrock landslides, smaller surficial slides, surface disturbance by anthracite coal mining, and orientation and jointing in Paleozoic sedimentary rocks is immediately evident in hillshade images derived from DEMs.

Ongoing surficial deposit mapping in Luzerne County is using the LiDAR to make final revisions on two 7.5' quadrangles and will use the LiDAR as a base layer on three 7.5' quadrangles this year. One of the most time consuming contacts to trace is between bedrock mantled by thin till (< 2 m) and thick till (> 2 m). The hillshade LiDAR image shows every minor bedrock ledge so the thin till areas can be almost entirely mapped out on the image with relatively few places needing to be checked in the field. This will greatly increase the accuracy of drawing the “Rock – Till” contact while also greatly reducing the amount of field work needed.

Early examination of LiDAR data from southwestern Pennsylvania suggests that these data will be an important tool for delineating landslides, as well as alluvial and colluvial soil and areas where bedrock is near the surface. We anticipate that the data will become an important tool for most future mapping in Pennsylvania.

More information on the PAMAP program is at http://www.dcnr.state.pa.us/topogeo/pamap/index.aspx