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LiDAR Home & Elevation Data Page
LiDAR Light Imaging Detection and Ranging ------------------------------------------------------------------------------------------------------
Links to Web Pages with LiDAR Information:
------------------------------------------------------------------------------------------------------ LiDAR uses the same principle as RADAR. The LIDAR laser sends a signal to the ground from an aircraft; some of this signal is sent (bounced) back to the aircraft; the time for the laser light to travel out to the ground and back to the aircraft is used to determine the distance to the feature on the ground that it bounced off. A tree is going to be higher (taller) than the ground it is on; a house is going to be higher than the ground on which it was built. The "lay of the land" is recorded to a great accuracy; in the case of our data here in Clinton County it is accurate in elevation to within a 6 inches. LiDAR data is composed of elevation measurements of the surface of the ground and were acquired during aerial topographic surveys, flown by Woolpert Inc in the Spring of 2004, and again as part of the OSIP Project in the spring of 2007. The file format used to capture the LIDAR data is referred to as "x, y, z", where x is the longitude, y is the latitude, and z is an elevation. __________________________________________________________________________________________
Above are some screenshots I did while working on a project for a property owner. The photography is the CIR.
Sample Screenshot of Aerial Photography taken in 2005 by the NAIP Program on the LEFT and a screenshot of the LiDAR Data Points in black and white on the RIGHT. Click to see the PDF's.
The image above shows LiDAR data of our Engineers Office, highlighting three Salt Barns; the Profile View shows the opening of the three structures. The image below shows a similar profile of Downtown Wilmington; the dome of the County Courthouse is easily seen.
The images below are of Wilmington, East of downtown, showing a TIN on the left and the same area from our 2008 photography on the right.
Below is an image of Wilmington showing a TIN, just the Bare Earth on the left and all of the LiDAR data in the right; buildings, vegetation, etc.
Part of the Village of Clarksville LiDAR - Screenshot from the PointVue program...
Clarksville area TIN (the lower left of the Clarksville grid)
Clarksville area TIN:
Light blue is the lowest elevation, light white / grey indicates the highest elevations. -------------------------------------------------------------------------------------------------------------------- Please review some of the sample TIN's (Triangulated Irregular Network) below in PDF format: Anliot-Davidson Nature Preserve TIN Terrell-Hanaghan Nature Preserve A TIN Terrell-Hanaghan Nature Preserve B TIN Collet Woods Nature Preserve TIN Some of the more interesting uses of this data is in creating 3D images, or 3D models of the earths terrain.
New Vienna, Ohio __________________________________________________________________________________________
__________________________________________________________________________________________ Download LiDAR Data / CAD Data As part of the "2-Foot Contour Project" we have implemented, each AutoCAD drawing file by tile has been made available for download. Each drawing file (in AutoCAD 2007) contains LiDAR points, 2-foot contours, and breaklines that were used to create the contours. Users of ArcView will be able to use this dwg data, and AutoCAD users will obviously be able to use this data. Since it is in version 2007 of AutoCAD, there may be translation issues... ...we have found a free program called DWG TrueView that may be useful in converting drawing files from one version of AutoCAD to another. It can be found at http://usa.autodesk.com/adsk/servlet/index?id=6703438&siteID=123112. Below is a screenshot of ArcView 9.2 viewing an AutoCAD drawing file, Tile Name A655512. Features that are of the most interest will be: - Points which are elevation points, made up of Spot Elevations, DTM which were derived from LiDAR, and Spot Elevations which are placed through compilation. - Annotation which is labeling of the Index contour lines and the spot elevation points. - Polylines which consists of Breaklines, Contour Index lines, Contour Intermediate lines, Contour Intermediate Depression lines, and Spot Elevation lines. The Spot Elevation lines is simply an "X" over top of the Spot Elevation point.
The best and easiest way of downloading the data you need is to use Google Earth as the front-end to find the area you want. You can use Google Earth as a front-end to download data in AutoCAD drawing file format by following the procedures below... Look at the County-Wide Grid to Download ACAD drawing files in Google Earth Click in the middle of the Tile Name you want that covers the area your looking for...note the screenshot below:
A window will open up that is a folder on our server that contains the drawing file (example - A640530.dwg) You can then download the dwg file to your computers hard drive for further processing or viewing. Below, users can download a Shapefile of the GRID that can be used to download CAD Data; same as the Grid above which uses a Google Earth / KML file, but is a shapefile for use with the ArcGIS family of Products...
__________________________________________________________________________________________ Here are some samples of what you can do with the dwg file, if you have ArcView (9.2). Click on the image to see a larger version.
__________________________________________________________________________________________ Executable to decompress the downloaded .laz file Here is a link to download a free viewer of LAS files... http://www.virtualgeomatics.com/index.html Using Google Earth for Downloading the LAS data - LiDAR Grid Below, users can download a Shapefile of the GRID that can be used to download LiDAR Data; same as the LiDAR Grid above which uses Google Earth / KML file, but is a shapefile for use with the ArcGIS family of Products...
The first step in using this data is having a program that allows you to process it. ArcView from ESRI with the 3D-Analyst Extension and Intergraph's MGE Terrain Analyst will allow you to process and use LiDAR data; CAD programs such as AutoDesk AutoCAD and Bentley Microstation may not be able to read LIDAR txt file data directly, but there are extensions and add-ons to the programs that will work. The file format of the LiDAR data will depend on the form of representation of the elevation data. It its raw form, LiDAR is a series of points stored as x, y, z, and probably an intensity and a class description field. Please see... http://www.clintoncountyohgis.org/DownloadData/LIDAR/LIDARClassDescription.pdf ... for class description documentation. __________________________________________________________________________________________
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