The Total Station
Today was our fourth day excavating Khow to Chung (KTC), and it’s been busy. However, before we start digging, sieving and analyzing, we have to do some basic, but crucial set up. Every morning we preview the day as a group before spitting into 3 excavation teams, each responsible for a different task. One of the most important responsibilities that everyone shares is the task of setting up the Total Station. The Total Station is an electronic instrument used by archaeologists to measure the distance, angle and height between the machine and any visible point. It is useful to archaeologists because it can measure the depth and location of the trench and any artifacts found within it.
Setting up the Total Station requires care, as it must be placed in the exact spot every day to ensure consistent and accurate measurements. To achieve this precision, the machine is placed over a datum point. A datum point is a specific and constant point from which measurements are taken. Our datum point is a bamboo stake hammered into the ground between trench A and trench B. During set up, the Total Station is placed directly above the datum point, level to the ground and at a height that is appropriate for everyone working. After programing some important information into the Total Station’s computer, like the height of the lens, it’s ready use!
Like so many jobs on the KTC site, using the Total Station requires teamwork and patience. At least two people are needed to operate the instrument. One person, holds a 1.5 meter pole with an orange prism mounted at the top in the exact location of the point to be shot. It is important to hold the prism still and level as moving or tilting it can cause errors in the Total Station’s computer. The second person, is the one operating the Total Station. S/he looks through a lens which moves along horizontal and vertical axis and focuses on the prism held above the point that will be recorded.
With the touch of a button a laser is shot from the end of the lens, reflected by the prism and recaptured by the Total Station. From the time it takes for the laser to return and the its position, the machine can calculate, the distance, angle and depth of the point. The operator then types into the machine what kind of point it is, for example the location of a piece of ceramic or a stone artefact of just the depth of the corner of one of our squares. We also keep a written record of each number and type of point we shoot. Later, the data collected in the Total Station’s computer will be transferred to a computer where it will be analyzed. We can even create a 3D map of the trenches!