The Awesomeness of LIDAR

I am regularly asked what I do for a living. This is a difficult question to answer. I spend a lot of time in front of a computer manipulating digital data into a custom product. That final product, as well as the data collection is defined by the client.  The client knows what their goal is and so defines what technology would best be suited to achieving that goal. Usually, a salesperson is involved in the decision about what technology should be used for collection as they are aware of our capabilities and the type of products that we provide. 

In this case, the technology is a remote sensing product called LiDAR, short for Light Detection and Ranging. To collect data using LiDAR, you need a plane with a LiDAR array on board that can simultaneously send a laser point and receive a laser point and record the data that returning laser point represents. The returning laser point does not actually contain any data, however data can be surmised by, for instance, how fast the light returns to the source or the intensity of the returning light.

The speed of the laser return can determine the elevation of the object that it hit before reflecting back to the source, once you take into consideration the known variables - the altitude of the aircraft or the speed of light through air. This data can then be recorded in a computer that can plot the information in XYZ ( or in three-dimensional space).  In the first picture, every point is a hit from a laser pulse.  As you can see, different objects are recorded at different heights, such as houses or trees. The colorization in the photo is color shading based on the height of each point. 

The intensity of the laser return indicates the reflectivity of the object that it hit before returning to the sensor.  Sometimes, if the laser pulse hits something that doesn't reflect at all (such as water or a new asphalt road), the laser pulse will not return to the sensor, which leaves a void in the data. For those wondering why water might not be reflective, the truth is that it is very reflective, but because of ripples or wave action, a laser pulse rarely reflects back in the same direction it came from after hitting water.  Notice in the second picture that the intensity reveals walkways that were not visible in the color shaded relief in the first picture.  

This final photo is a combination of the color shaded relief and the intensity image above. This image allows you to see the heights of features as well as the detail of other surrounding features. 

Isn't LiDAR amazing?