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Crop Agriculture

About LiDAR-Based Elevation Data and Where it is Available for Free

Related pages: LiDAR-based elevation, topography, and drainage layers    Elevation data accuracy

Original source vs. USGS LiDAR-based rasters 

 LiDAR elevation GIS 3D rendering with flow lines and sinksLiDAR elevation and drainage

LiDAR is an acronym for Light Detection and Ranging that derives elevation values by laser pulses being emitted from an aircraft then essentially measuring the time it takes to detect the reflected signal.  LiDAR can be calibrated to acquire elevation for the bare earth surface (transmits through vegetation) which is preferred for agriculture. LiDAR is initially acquired as points; the points can be processed into continuous elevation rasters. The USGS acquires LiDAR from different partners throughout the United States and makes elevation rasters available on the National Map as a 1/9 arc-second product (approximately 3 x 3 meter resolution); the process includes the USGS making improvement to the data. National Map bare earth elevation rasters are the preferred source. There may be 1/9 arc-second elevation products that are not based on LiDAR (metadata should described source of particular data). Areas where LiDAR-based elevation data are available include the entire states of Iowa and Ohio as well as parts of other states. There is no centralized source to acquire all LiDAR data available in the United States, although the USGS aims to develop such a single source. The following link provides access to current National Map LiDAR information and availability of 1/9 arc-second data (there are 1/9 arc-second data that are not based on LiDAR, which can be determined from the metadata). When you access the link, scroll down to the release notes (opens in new tab) to find where 1/9 arc-second elevation data is available:

USGS National Map 1/9 arc-second LiDAR-based elevation data status and locations (opens in new tab)

 

Other links for National Elevation Dataset (NED) information are: 

NED homepage (opens in new tab)

NED metadata downloads (opens in new tab)

 

A way to experience LiDAR-based elevation interactively is to download free Quantum GIS, then download the LiDAR-based elevation map data available in the Agricultural Custom Downloads folder in the Free section.

The point (post) spacing of LiDAR varies; however, a LiDAR point is typically acquired every 1-2 square meters. Overall, LiDAR can ultimately be the basis for elevation data that can be accurate enough to be applied for agricultural applications; in particular, useful drainage and hydrologic data can be produced in addition to providing elevation for a field. However, as shown in the (jpg) Further smoothed page in the LiDAR-based elevation maps folder, further processing to smooth data may be necessary to derive useful topographic layers.