Mapping: “X Never Marks the Spot”

By Erina,

Mapping is an important part of any archaeological project. By creating a detailed site map, you can store information about terrain, elevation, feature location, and most importantly, the spatial relationship between features. To map the site we are working on this season, we are using a total station. To map a site with a total station you need two people, one to run the total station, and another to venture out into the site carrying what we call the “pogo”, which contrary to what the name suggests is not used for jumping. Rather, the pogo is a rod with a prism attached to the top, which is used to bounce back the laser that shoots from the total station.

Photo: N. Leclerc Erina using the "Pogo".

Photo: N. Leclerc
Erina using the “Pogo”.

The total station measures the time it takes for the laser beam to return and uses the difference in time to calculate the distance from the station to the rod as well as other attributes such as elevation. The total station also allows for more complex functions such as coding, which allows us to map features. The data stored in the total station is then used to create a high definition topographic map. As always, the outcome of your map depends on the quality of the points that are collected in the field. Mapping heavily forested areas such as the site which we are working this year presents many obstacles. The first obstacle we encountered was the view obstruction by trees and branches. The more trees and other obstructions there are on site, the more times that the total station operator has to change location. While it is necessary to change the location a few times to get a whole view of the site, too many changes can result in the accumulation of error when calculating future points, and therefore affects the overall quality of the map.

Photo: N. Leclerc Aidan looking through the total station.

Photo: N. Leclerc
Aidan looking through the total station.

Site maps can also be created by hand, and points can be collected and recorded manually utilizing other tools such as a transit and stadia rod, but this method is much more labour intensive and requires the operators to record and calculate all points by hand, which can lead to human error. This makes me very glad that we are using the total station, which in essence works like computer, capable of computing calculation on the fly and recording them in its database. In addition, these calculations are calculated to a much higher degree of accuracy than any calculations done by hand. Standing in the site and observing the surrounding features is one thing, but once we have a map on hand, we will be able to assess the location and spatiality of the features to a greater extent, hopefully allowing us to gain greater insight on their construction and use.

Gary teaching students how to map using the "Old School" transit and David looking through the "High Tech" total station. #outwiththeold #inwiththenew

Gary teaching students how to map using the “Old School” transit and David looking through the “High Tech” total station. #outwiththeold #inwiththenew

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