GIS Event Calendar

Topographic LIDAR in New Hampshire

In collaboration with the NH Geological Survey at the NH Department of Environmental Services, GRANIT is actively working to expand the coverage of LIDAR data available in New Hampshire. There are many online resources available to learn more about this data asset, but we hope this page provides a valuable starting point for those interested in learning about LIDAR and discovering what data sets are currently available in the state.

Please explore the following sections of this page:

What is LIDAR?
What applications can LIDAR support?
Why do we need LIDAR in NH?
What data sets are available in NH?
How do I access the available data sets?
What other resources are available?

What is LIDAR?

LIDAR (LIght Detection And Ranging) is a remote sensing technology that uses light in the form of pulsed laser to examine the surface of the earth. Topographic LIDAR uses pulses of light emitted from a near-infrared laser mounted in a small aircraft to “scan” the land surface below. The LIDAR sensor detects the travel time of reflected energy from each laser pulse. The collected data, known as the “point cloud”, represent reflections from the ground, as well as any vegetation, buildings or other solid surfaces. The raw data points may be processed to create a “bare earth” model which reveals unprecedented topographic details as though all vegetation and buildings or other structures have been completely stripped away. Other products, including traditional contours, may also be generated.

Credit: Schreppel, H.A., and Cimitile, M.J., 2011, Lidar postcards:
U.S. Geological Survey General Information Product 124, 4 p.

LIDAR Capture

A short video explaining the basics of LiDAR, produced by the National Ecological Observatory Network (NEON), is available here.

What applications can LIDAR support?

Topographic data provided by LIDAR will support accurate mapping of flood inundation zones, and thereby protect public safety and infrastructure and avoid costs associated with flood damage. Other uses of LIDAR relate to the identification of the pathways that water and contaminants follow across the landscape. Enhanced elevation data enable much more accurate delineation of watershed boundaries as well as detailed mapping of drainage channels, both natural and manmade, that collect, store, and transmit storm water runoff. Engineering costs of new roadway designs and other land development projects can be significantly reduced to the extent that alternative plans can be more easily evaluated and reviewed with respect to local site conditions. Geologic hazards such as potential landslides can be identified based on the specific landforms that are revealed by viewing bare earth LIDAR. Search and rescue operations can successfully avoid obstacles in rugged and difficult terrain. Cost-effective characterization of forest resources, in terms of both their commercial and ecological values and the distribution of fire fuels, represents another benefit. Other uses are as diverse as mapping potential for development of solar and wind energy, understanding potential coastal impacts of sea level rise, or modeling the dispersion of radioactivity in the event of an accident at the Vermont Yankee or Seabrook power stations.

Why do we need LIDAR in NH?

Credit: NH Geological Survey
LIDAR Capture
Accurate data that record the elevation and shape of the land surface (i.e., topography) are critical to support land development projects, to protect public safety, and to manage natural resources. The graphic on the right illustrates products derived from the 10- and 30-meter resolution Digital Elevation Models (DEMs) that have traditionally been available in New Hampshire (middle and right panel). Note the sharp contrast in the level of detail between those two images and the 2-meter resolution image (left panel), which is a product of the 2011 coastal LIDAR data collection.

A number of key reports have recommended the acquisition of statewide LIDAR in New Hampshire, including:

  • Water Sustainability Commission Final Report (December 2012) - goal 6
  • Comprehensive Floodplain Management Commission Final Report (September 2008) - finding 6.1.6
  • NH Geographic Information System Strategic Plan (October 2007) - priority 5

    What data sets are available in NH?

    The major LIDAR acquisitions available from GRANIT are shown in the image below. A downloadable version of this status map is available here.
    LIDAR Status

    As shown in the image, major collections include:

  • Coastal Shoreline - acquired November 2013 through April 2014
  • Coastal LIDAR Data Sets - acquired Winter 2010/Spring 2011 and Spring 2014
  • Connecticut River Basin/Winnipesaukee - acquired Fall 2015 through Spring 2016
  • Merrimack River Basin - acquired Winter 2011
  • Nashua River Basin - acquired May 2011
  • Umbagog Collection - acquired November 2016 through May 2018
  • White Mountain National Forest - acquired November 2010 through November 2014

    How do I access the available data sets?

    Please visit the GRANIT LiDAR Distribution Site to review and download available data sets. Datasets are organized by collection area, with the content of each collection area comprising one or more of the following data types:

  • Bare Earth DEM - Digital Elevation Model representing bare earth terrain.
  • Point Cloud LAS - Complete dataset of all data returns.
  • Classified LAS - LIDAR point cloud data, where the points are classified to indicate the type of surface hit by the pulse. Classification codes were defined by the American Society for Photogrammetry and Remote Sensing (ASPRS).
  • First Return/Last Return LAS - Portions of a LIDAR pulse may be reflected by vegetation before reaching the ground. The First Return represents the highest elevation surface to reflect the pulse (e.g. tree canopy), and the Last Return is the lowest elevation surface (e.g. the ground, buildings) reflected by the pulse.
  • Intensity Images - Intensity is a relative measure of the return strength of the laser pulse, which depends in part on the type of surface hit by the pulse. Intensity images look similar to black-and-white aerial photographs in which brighter areas indicate more highly reflective surfaces.
  • Data Footprint - Spatial extent of a specific data set or collection.

    What other resources are available?

    There are numerous web resources available to learn more about LIDAR. Below please find a partial list of those that we find useful:

  • Introduction to Lidar - Self-guided online training resource developed by the NOAA Office for Coastal Management that explains how lidar data are collected, what kinds of information they contain, what products can be derived, etc.
  • Maps Made With Light Show the Way - a Story Map describing a new initiative by USGS to create a national elevation map using LiDAR.
  • "The Bare Earth" - a beautiful story map presentation on the use of LIDAR to support geologic applications in the State of Washington, developed by the Washington Geological Survey.
  • Open Topography - National Science Foundation-supported portal to high resolution topography data and tools from the US and around the world.
  • The National Map - USGS portal providing access to geographic information from a collaboraton of USGS and other federal, state, and local partners.
  • 3D Elevation Program (3DEP) - information on the national effort to develop high-quality topographic data.

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