Lidar Talking Points Pennsylvania has an immediate need for new lidar (topographic) data coverage. Some uses of the data are enumerated later in this document. USGS has calculated an average return on investment for lidar at 5:1. If we can act in the 2018 budget year, we have the opportunity to apply to the USGS 3DEP program to cover 30-40% of the project cost. Status of lidar collection in Pennsylvania The first complete lidar coverage of the state of Pennsylvania was made over a three-year period from 2006 to 2008, by the PAMAP program. The program was funded primarily by DCNR, with contributions from other state agencies (OA, PennDOT, PEMA, DEP), USGS, and FEMA. The data has a vertical accuracy of 18.5 cm; 2-foot elevation contours and 1-meter digital elevation models (DEMs) were produced. This product cost about $15M, and has since informed billions of dollars of site engineering, planning, environmental management, and investment. These existing 10-year-old lidar products are the most-downloaded data on the state geospatial data clearinghouse despite the fact that, in many locations, the data does not reflect current on-the-ground conditions. In the intervening 10 years, technology has improved so that current standards (QL2) are vertical accuracy of 10 cm, yielding 1-foot contours and 1-meter DEMs. Eight counties in southeastern Pennsylvania have been collected at QL2 under the USGS 3DEP initiative. Allegheny County paid for its own collection in 2015. NRCS and USGS 3DEP are currently in the process of contracting for QL2 lidar for 13 counties in the Chesapeake Bay watershed in central Pennsylvania (see attached map). An ad hoc group of state, federal, and local government agencies and non-governmental organizations (NGOs) have come together as the Lidar Working Group to work toward a complete QL2 lidar coverage of the state, and to plan for data management and maintenance into the future. Agencies currently represented include: PEMA, DCNR, PennDOT, DEP, PA Game Commission, USGS, NRCS, National Forest Service, PASDA, Shippensburg University, PA Magic, PA MAPPS, Susquehanna River Basin Commission. Estimated cost and timeline A current estimate for the cost of obtaining QL2 lidar for the remaining 45 counties is about $7.6 million (33,337 sq. mi. x $226/sq. mi.). On average, the 3DEP initiative covers about 36% of the cost of successful proposals, bringing the cost to the state and other partners closer to $4.8 million. The work would likely be completed as a two-year or perhaps three-year project, thus reducing the cost per year to partner agencies. The aim would be to line up partners within and outside state government, and submit a proposal to 3DEP in September 2018. Ideally, the partners would look at refreshing the elevation data on a 3-7 year cycle. Some determining factors are technological advances leading to improved data accuracy at comparable or reduced cost, coordination with PEMA orthophotography cycle, and rapidity of change on the ground. 1
Uses of lidar data Lidar data is processed to produce a variety of data layers, including height of tree canopy, building locations and heights, bare earth DEMs, and elevation contours. Some examples of applications of the data follow: Flood or inundation modeling o Use case: Cambria County s GIS Director used the 2006 PAMAP lidar data to enhance building information for the county s updated Hazard Mitigation Plan (HMP). First, he enhanced building footprints using the 2006 data. Then he used elevation data to figure rooftop heights and ground elevation for each building. Using a little math, he derived number of stories per feature, and first floor height above ground. This input is required for the GIS analysis to model estimated flood level within a building and calculate property loss values for each building. The project relied heavily on the accurate elevation values provided by the lidar data. Counties are required to update HMPs every five years, demonstrating the need for regular updating of lidar data. FEMA 100-year floodplain (depth grid) near Johnstown, PA displayed with 3D building heights and data, all derived from lidar and used to update the Cambria County Hazard Mitigation Plan. Building colors show the dollar loss estimate, with higher values in orange and red. (Cambria County GIS Center) Land cover Elevation data can be used to categorize the land surface into forest, water, agriculture, impervious surface, etc. o Use case: DCNR partnered with the Chesapeake Conservancy to analyze riparian forest buffers (35-foot buffer along streams) in the Susquehanna Watershed. The PAMAP lidar was used along with imagery to generate a 1-meter landcover dataset along with an improved hydrography layer. This analysis was not possible without lidar as previous data was insufficiently precise to resolve a 35-foot buffer. Forest canopy heights Total height of the forest canopy is used by forest managers to identify poor, average, and superior sites for growing trees. This data is also used to map 2
areas of State Forest understocked with trees, and to map forest stands (groups of similar trees) Base maps Lidar and its derivatives (DEM, slope, hillshade, contours) provide a standardized base map for cartographic products and geologic maps, as well as for accurate mapping of vector layers such as road, trails, and streams. Lidar-derived hillshade showing bare-earth surface. Blue lines are streams. Red lines are trails. (PA DCNR, Bureau of Forestry) Hydrography and flow-path mapping; storm water infrastructure needs (MS4). o Use case: Our present water base map is about 40 years old and largely schematic. When overlaid on modern imagery and topography, streams plot outside of their valleys and do not map to their full extent. Research in Lancaster County illustrated the difference in extent of current base mapping and that which can be derived from modern lidar. Comparison of the current state standard hydrography (left) and the same area enhanced with lidar and flow accumulation study; Upper Chiques Creek, Lancaster County. 3
Archaeological and historical preservation needs Delineation of geologic hazards, such as landslides and sinkholes Wetland determination Infrastructure management Energy and mineral resources Change mapping Comparison of previous lidar datasets to new lidar datasets allows analysis of changes in landcover, land use, and hydrography. New Marcellus well pads incorporated into PAMAP lidar DEM to compare hydrography before and after well pads existed. (PA DCNR, Bureau of Forestry) 4