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The USGS continues to collect high resolution elevation data, contributing to greatly improved Alaska map data
In late 2012, the USGS in conjunction with several other Federal, State, local, and agencies met to address mapping Alaska. Despite the attention paid to America’s largest state, modern mapping information did not exist over the majority of the land mass. Aviation safety, energy development, resource assessments, flood plain management, natural resource conservation, recreatopm. and a long list of other impportant activities depend on access to accurate, up-to-date topographic maps and data.
Alaska mapping status map showing 84% statewide IfSAR coverage available or in work as of May 2017. (Click to enlarge) (Public domain.)
Thus, the Alaska Mapping Initiative (AMI) was planned, formed and started.. The goal of the AMI was to acquire and enhance foundational digital map layers such as elevation, surface water, and boundaries that will be used to produce new US Topo maps for Alaska. Of those layers, elevation is critical and is the basis for topographic map production.
Lidar, short for “Light detection and ranging”, is a remote sensing method of studying the Earth and surface characteristics. This technology, often from aircraft, uses light in the form of laser beam pulses to measure ranges and distances reflected from the ground. These thousands of pulses per second are translated into highly accurate and precise elevation data. However, because of Alaska’s remote locations and frequent cloud cover, the USGS is collecting the elevation data through the use of Interferometric synthetic aperture radar (IfSAR).
The new data are replacing decades-old 60-meter resolution elevation data that have known vertical and horizontal errors. As of June 2017, 84% statewide IfSAR coverage was available or in work. It is anticipated that an additional 6% coverage will be added using end-of-year funds late in fiscal year 2017, reaching 90% total statewide coverage available or in work.
A recent literature search discovered dozens of scientific journal articles that cite the use of this new data in a variety of critical and routine issues and applications. In addition, the new data is part of the ongoing 3D Elevation Program (3DEP), which is an 8-year program to coordinate and collect enhanced elevation across the nation, including Alaska, Hawaii and the US territories.
Alaska IfSAR elevation data can be downloaded through The National Map data download service.
About IfSAR Acquisition
The USGS is using its Geospatial Products and Services Contract to contract the collection of five-meter resolution elevation data using IfSAR sensors flown via aircraft. Deliveries include a Digital Terrain Model (DTM) representing the bare earth, a Digital Surface Model (DSM) representing the tops of vegetation and structures, and an orthorectified radar intensity image (ORI).
Note that some of the stated Alaska IfSAR coverage, specifically that over the National Petroleum Reserve-Alaska (NPRA), was collected under slightly different specifications prior to the current effort, which began in 2010. The USGS plans to complete IfSAR collection by 2020, including an update of the legacy NPRA data.
The USGS is coordinating with the State of Alaska and multiple Federal agencies to accomplish these tasks through the Alaska Geospatial Council and the Alaska Mapping Executive Committee. IfSAR data are being used in a wide variety of mapping, resource management, and human safety applications.
Alaska Mapping Initiative: Frequently Asked Questions
