LIDAR

LIDAR: Laser Imaging Detection and Ranging

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. 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, which is what we have made available on the downloads section of this web page. Because the data sets are so large, they have been clipped and cut up into a number of sections, each section belonging to a township. Please refer to Data Availability by township sections for more information on downloading.

LIDAR Raw Data Sample:

"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.

Click here to learn more about LIDAR and it's uses from other web pages.

All of our contour data was developed using LIDAR information. Some of the more interesting uses of this data is in creating 3D images, or 3D models of the earths terrain. Please review some of the samples 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