Concept Clearinghouse

Portugal, surveying, the Nikon Total Station and me!

I just got back from my occasionally frantic trip to Portugal to assist with the setup and use of the Archeology Labs' fancy new Nikon Total Station.

The trip was wonderful, first of all. It was my first trip to Europe, and EVERYTHING was new. Before the trip, I knew a tiny bit of French, a functional amount of Spanish (Mexico type), and of course my native English. By the end of the trip, I knew a little bit of Portuguese, and was getting better. (I had mastered several phrases in addition to the usual requirements of "Two beers, please", "Where is the bathroom?" and "I need a doctor".)

The trip went from the Greensboro, North Carolina airport to Boston's Logan International Airport, to Paris' Charles DeGaulle Airport, to the Lisbon Airport, all Delta flights operated by Air France. On the way back, the flights went from the Lisbon airport, to Frankfurt, Germany, then to Philadelphia, Pennsylvania, and finally to the Greensboro airport, all US Airways flights operated by Lufthansa (a German airline). This chain of different airports, plane sizes and airlines led to several discoveries:

Now, on to the real cool stuff...

Working in Portugal

The point of this trip was actually to get some work done, even though it was also a fun and interesting trip.

To put it simply, the Archeology Labs at Wake Forest University (where I work) bought some new equipment for surveying sites, and the yearly fieldschool in Portugal was going to be host to the first field trial. Since I'm the technology guy for the department (and because the director of the Archeology Labs, Paul Thacker is a great guy!), I earned a trip to Portugal to make sure that the massive investment in this equipment (not only the purchase price, but the logistics of getting it into Portugal) would not be wasted.

The heart of this new equipment was a Nikon DTM-952 Total Station. If you don't know much about surveying (I knew virtually nothing before this trip), this is a complex device which uses a laser to measure the exact distance and angle from the device to the target (basically a prism on a staff of known length). By this measurement, one can tell how far North-South, East-West and the change in elevation from the reference point (a target due north from the device, for instance), measured in millimeters.

The Total Station allowed us to very accurately measure the surface topography of the sites being studied, as well as to mark the precise relative location of various features within the site. The surface topology was very important so that we could adjust the ground penetrating radar signals (another nice piece of equipment taken on this trip), so that the radar would "know" when it wasn't pointing straight down (going up a hill, over a bump, etc.).

You may be asking yourself why I was even on the trip if I didn't know anything about surveying before I went. Well, one of the strengths of the Total Station is that it not only records very precise data, but it can also output that data to a computer through a serial cable. Most computers (including the Thinkpads used by WFU) don't have serial ports anymore, and few people are familiar with the nuances of serial communications. So, to make sure they didn't have to sheepishly jot down the measurements from the LCD screen of the Total Station, I went along to make sure the data got into the computer in a usable form. This involved a USB to Serial adapter, the drivers to make it work, and some fiddling around with settings. (Don't even think about jumping into this with only the Nikon Total Station manual. It has information about the fields output in its comma-delimited data, but only about one sentence on how to get the data out. There is no information about what program to use, or any information about serial communications.)

Luckily, I had about a week before we left for Portugal (really only two days was dedicated to the Anthro. Department, and therefore the Arch. Labs) to play with the Total Station. This went very well, and I thought I had already done the "heavy lifting". ("Oh, great! Now what am I going to do in Portugal to prove that I was needed on this trip?")

As it turned out, it did pay off to bring me to Portugal, because, although I had documented the heck out of how to use HyperTerminal to capture the output from the Total Station, as so often happens, things were a little different in the field. Since the tests done here in Winston-Salem were brief tests, involving only a few "shots" from the Total Station to targets, everything worked out beautifully when re-using the same HyperTerminal session. Unfortunately, in the field, at the actual sites, we were shooting 250+ shots at a time. This meant that Hyperterminal basically overflowed its screen buffer, resulting in a large amount of data that couldn't be deleted from the session. After the first set of data was downloaded, everything afterwards (except for the one screen worth that could be deleted) mixed with the new data, resulting in a useless data soup!

I setup a new HyperTerminal session, re-wrote the documentation to tell others how to setup a HyperTerminal session, and everything went well.

Then came massaging the data. The guys running the ground penetrating radar (GPR, a very cool device as well) needed the data in simply x,y,z format, with no headers, and we needed to get approximate measurements in between the points we actually measured, so the GPR guys would have measurements every meter in both directions. In comes Surfer and some magic by Dr. Paul Thacker (Director of Archeology and my magnanimous host). The data was massaged to take out human errors in shooting ("I could have sworn we shot that point!"), Surfer was used to interpolate the data between the shots we actually recorded, and the data was passed to the GPR guys.

We worked on two sites, one a medieval collection of storage silos (one theory was that these were used communaly by the nearby village to store items on which they didn't want to pay taxes) and a castro, or hill fort, created in the late Bronze Age to guard the nearby town. (It was probably used as a place of refuge for the villagers when under attack.)

Both of these sites were excercises in understatement. Some of the silos were empty, dug out long ago, and the others were only represented by slight depressions in the surface where the plants seemed to grow a little more easily. (The relatively loose soil of the silos, with better drainage and aeration serves to encourage root growth.)

The castro (Castro do São Martinho) was also not much to look at, unless you count the fabulous views of the underlying valley. Some remnants of an ancient stone wall here and there were the only indications that this was not just more farmland with a great view. It was maybe sheer luck that this site was not more disturbed. One side was partially planted with eucalyptus trees (the new fad cash crop of Portugal), and another side had been plowed and planted with potatoes in the past, but nothing had been dug up, and the existing stone walls weren't knocked down, so there could be some fantastic finds in store for the WFU Archeology Labs. (I was just there for a few days, to get the Total Station going, and make sure that others could operate it when I left; I didn't get to stay for the actual excavation, which will come after weeks of surveying and measuring.)