The PAMAP Program has completed an unprecedented project to collect and process high resolution LiDAR elevation data for the entire state. Pennsylvania is one of the first states in the nation to complete collection of this level of elevation data for the entire state. In spring 2006, the PAMAP Program began the project with the capture of LiDAR for 21 counties in the western part of the state, along with Luzerne County. LiDAR was acquired for an additional 21 counties in 2007 (see map below). Acquisition of the 2008 data was completed in the spring of 2008.
The opportunity to collect and provide LiDAR data is quite advantageous to the Commonwealth. In evaluating various options for LiDAR collection and processing, it became apparent that there would be significant synergies in combining the orthoimagery and LiDAR efforts. Independent study of the joint project proposal confirmed substantial cost and workflow savings could be realized by combining efforts. Therefore, the Program chose to collect both orthoimagery and LiDAR under one contract for all 67 counties, and complete a high-resolution elevation data set for the Commonwealth.
LiDAR, an acronym for light detection and ranging, is used to produce various elevation data products including point based digital terrain models (DTM), grid-based digital elevation models (DEM), and contours. In addition to these “end user” products, LiDAR processing generates other data resources, including the raw point cloud, processed points, and breaklines.
The LiDAR data is primarily acquired to produce an accurate and high-resolution bare earth model of Pennsylvania. One of the primary uses of the bare earth model is to support floodplain mapping and flood control projects. The LiDAR data is collected and processed to generally meet specifications called for in FEMA's Guidelines and Specifications for Flood Hazard Mapping Partners. The data is collected with a 1.4-meter average point spacing (2-meter maximum) with a bare earth surface vertical accuracy of 18.5-centimeters RMSE. Data is in tile form using the PAMAP 10,000-foot tile index. All products are in the public domain. The data products include:
- LiDAR Point Cloud – the LiDAR points are distributed in the binary LAS format. Each point is attributed for intensity, classification, etc. according to the LAS standard and PAMAP specifications. The metadata distributed with the LAS file provides details on the classification. The size of each LAS file varies based on terrain and features, among other variables.
- Digital Elevation Model – a 3.2-foot pixel (1-meter equivalent) raster GeoTIFF Digital Elevation Model (DEM). Each pixel in the DEM has an interpolated elevation value. Each DEM is approximately 37.5 MB in size.
- Contours – a 3D shapefile of 2-foot contours is provided for each tile. Each contour is attributed with its elevation value and whether it is an intermediate (2- foot interval) or index (10-foot interval) contour. The size of each shapefile varies.
- Breaklines – a 3D shapefile of breaklines is provided for each tile. The breaklines are interpreted from the PAMAP orthophotos and the LiDAR data is used to provide elevation (z-values) to each line. The breaklines are produced for the classification of the LiDAR data and enhancement of the contours. The breaklines are not produced for engineering use. Each breakline is attributed for feature type (e.g. edge of road); the feature types are documented in metadata. The size of each shapefile varies.
The status of the LiDAR project (December 2010) is shown below.
Where to get Data
PAMAP LiDAR and derived products can be acquired from the following organizations. Data may be available from other sources as well.
DEMs, contours and breaklines as well as LAS files are provided through FTP and map services at the Pennsylvania Spatial Data Access Clearinghouse (PASDA).
The point cloud data in LAS format is also available through the USGS Center for Lidar Information Coordination and Knowledge (CLICK) at http://lidar.cr.usgs.gov/LIDAR_Viewer/viewer.php.
All data products are available for bulk and/or offline acquisition from the Pennsylvania State Data Center here.
Information on data issues for PAMAP LiDAR and elevation products can be found here.
Frequently Asked Questions
The Program’s LiDAR Frequently Asked Questions (FAQ) can be found here.