First, I’d like to say how much a enjoyed the event last Saturday at Hills Tower. It’s a real privilege to be shown around places that provide snapshots into both social history and the history of the surrounding landscape. Thank you very much to Gibbs for showing us around their home, the estate map, and providing such an informed narrative.
Archie gave me the opportunity to talk about the project I’m working on, which I failed to elucidate on as I’ve a few teething problems. However, I’d thought I’d try and correct this here. I’m a student at the University of Glasgow doing an MSc in Geospatial Technologies and Cartography. The project I’m working on revolves around assessing historical estate maps as representations of the landscape, and their utility in mapping landscape change over time. As I’m doing an MSc in geomatics I’m focussing on the geometric aspects of this, but my background is archaeology and I’m very much aware that this is not the end of the story.
In a nut shell, if we’re going to georeference these maps in a digital form and use them for obtaining measurements or locating boundaries, we require an assessment of the digital version as a representation of the original, and an assessment of historical maps as a representation of the historic landscape.
Over the next three months of my MSc project I’m considering aspects of the original map production, the capture of these maps in a digital format, and how we locate (georeference) them on modern map data. As such, I’ve been researching 18th century surveying equipment and techniques, and the effects of ‘noise’ produced from different types of scanners, and the problems of lens distortion associated with digital photography.
What I found really interesting about the estate map at Hills Tower was how well it georeferenced to Google Earth across the entire map space. Two important dates in the development of surveying equipment, at least from what I’ve gleaned from my rapid researches, are 1725 and 1768. In 1725 John Sissons fitted a telescope to theodolites replacing sights. In 1768 Jessi Ramsden invented the Dividing Machine which mechanically engraved the graduations of hours, minutes and seconds upon the arcs and circles fitted to the instruments which measure angles. Prior to this, graduations were engraved manually and must have produced instruments of varying accuracy. Added to this, simpler instruments such as the plane table and the circumferentor are likely to have been used to produce much of the survey, even if a theodolite was used to locate surveying stations (instrument control) across the area.
When all this is put together, over such as undulating landscape, it is really encouraging how well the Hills Tower map can be georeferenced to Google Earth. If anyone has an interest in or information on 18th century, or earlier, surveying I’d love to hear from them. My interest is very much in the problems a land surveyor would have faced with the technology of the time. I’m very much a technician as a surveyor myself, being trained by the archaeological rather than the engineering profession, but I have used a non-electronic theodolite, survey book, and calculator in anger before so appreciate some of the issues these earlier surveyors faced.
Finally, again a big thank you to the Gibbs family, and I’m looking forward to more DAMP events later in the year.