LIDAR
Laser Imaging Detection and Ranging
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3D Models and Images Sample Maps showing LIDAR Generated TIN's
LIDAR Raw Data Sample Web Pages with LIDAR Information
Contours Download LiDAR Data (used in creation of 2 foot contours)
LIDAR Class Description Download LAS LiDAR Data
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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 inch error factor.
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. Below is a sample of raw LIDAR data.
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"X","Y","Z"
1553340.90999999990,571903.60999999999,873.69000000000
1553348.93999999990,571903.73999999999,873.60000000000
1553357.88999999990,571903.85999999999,873.43000000000
1553367.70000000000,571904.03000000003,873.32000000000
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.
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Sample Maps showing LIDAR Generated TIN's
Please review some of the sample TIN's (Triangulated Irregular Network) below:
Anliot-Davidson Nature Preserve TIN
Terrell-Hanaghan Nature Preserve A TIN
Terrell-Hanaghan Nature Preserve B TIN
Collet Woods Nature Preserve TIN
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Click to learn more about Contours.
All of our contour data was developed using LIDAR data.
Click to view the "2 Foot Contours Project"
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Some of the more interesting uses of this data is in creating 3D images, or 3D models of the earths terrain.
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New Vienna, Ohio
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Video of just the TIN for Tile A3
Virtual New Vienna, Ohio Another Virtual New Vienna, Ohio
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Web Pages with LIDAR Information
NOAA & LIDAR City of Dallas GIS & LIDAR Information
Indiana Spatial Data Portal LIDAR and New Orleans
LIDAR and USGS Ohio Archaeological Council - Using LIDAR in Archaeology
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After careful consideration, we will be changing how we offer up LIDAR data for download. It will be more efficient to make the LIDAR data available in the same way that other elevation data will be made available, which will be in an AutoCAD data format.
As part of the "2-Foot Contour Project" we have implemented, each AutoCAD drawing file by tile will be 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 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 looking at 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 are 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.
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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.
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Executable to decompress the downloaded .laz file
Using Google Earth for Downloading - LiDAR Grid
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