LiDAR

To begin the New Year, I think it would be a good idea to take a step back from learning about actual archaeological sites, and look at just a few of the many hundreds of methods that Archaeologists use to learn about ancient sites. Many of these involve technology and a bit of science, so let’s get into it and see what we can learn! Let’s begin, in fact, with a process known as LiDAR.

 LiDAR stands for light detection and ranging. This process is similar to the better-known RADAR. Basically, with LiDAR, a laser pulse is sent out from a transmitter (a machine which releases the laser). The laser is made up of particles of light, called photons. The transmitter ‘shoots out’ photons, and when they hit something, they ‘bounce back’ to a ‘receiver’. The job of the receiver is pretty self-explanatory – it receives the light! The light is then funnelled into a detector which counts the photons and, using the speed of light, works out how long the light took to make its trip. Please don’t get bogged down with details here. This illustration may help to explain the concept.

LiDAR Concept

 So how does this help Archaeology? Well, it turns out that LiDAR can do something pretty special. When the information is sent to the detector, the detector (using the information of how long the light took on its round trip) draws a picture of whatever the light was aimed at. So imagine if the LiDAR was fired to earth from an aeroplane. It can be hard to see the earth well with the naked eye – and as an Archaeologist, you need a bird’s eye view. So the LiDAR is fired towards earth – and soon you have a picture you can enlarge and take as long as you want to study.

LiDAR image, seen from the sky

 And how does the making of the picture work? When the light takes longer to come back to the detector, it is obviously taking longer to find something to bounce back from. In the aeroplane example, this would mean that the ground is further away. If it is quicker coming back, the earth is closer. I’m sure you can work out why this is important. If there is a clear scan of the earth, it will show any dips or raised areas in the earth. This may show places where a burial mound used to be, or an area where an underground arch has collapsed. Using this, Archaeologists can now narrow down the area where they need to excavate. Clearly, LiDAR is very important to the Archaeological method.

 Thank you for continuing to read into the New Year, and I’ll see you next week! If you have any questions, please feel free to ask!

 Stay curious!