LiDAR-Based Elevation Comparison for a Field
The data include layers that have been saved as a Quantum GIS (free software) map project so all you need to do is open the project in Quantum. Quantum can be downloaded from the Quantum (user-friendly) page in the GIS software folder; instructions to open Quantum GIS projects are in the About downloading page in the Agriculture Custom Downloads folder. It is not necessary to use Quantum GIS (layers will open in other software such as ArcGIS).
To download, left-click, then click OK to save file to your computer. The file will be in a compressed format; there are steps describing how to extract the data within the compressed (zipped) files in the About Downloading page.
Data download:
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Data Description and Map Image
LiDAR-derived elevation comparison: Includes elevation layers both based on LiDAR but with different resolution. One elevation grid is from Ohio Geographically Reference Information Program (OGRIP) with 2.5 foot resolution, the other is from The USGS National Map Seamless Data Viewer for the same extent that has been projected to an 11.2 foot resolution. The USGS acquires LiDAR-based elevation from different sources, works with it to improve it, then projects it to approximately a 3-meter average resolution. National Map data spatial reference upon download is in NAD83 geographical coordinate system, as a result pixels have different length north-south and east-west sides until projected into a UTM or state plane system; the average dimension of the pixels is about 3 x 3 meters though. For comparison purposes of elevation at different resolutions here, the data was projected to an 11.2 foot resolution with bilinear interpolation; each National Map-based pixel is 20 times larger in area than the OGRIP pixels. The data is for an agricultural area in Ohio, USA. There are also points included that have been converted from the actual LiDAR (.las) dataset. It is important to realize that LiDAR elevation data are acquired first as points, then area typically processed into continuous layers of elevation data. There are usually correction and smoothing techniques performed to the raw data to produce an elevation grid. There is additionally an empty polygon shapefile that can be used for practicing polygon editing.
Screen capture when opening map in free Quantum GIS
