How to map a new country?

Update: DVD released on 24 July 2017. We have one copy of the DVD to give away. Just retweet this message by 12 noon on Friday 28 July: https://twitter.com/OrdnanceSurvey/status/889486114536476674

March 24 sees the UK film release of Lost City of Z. It chronicles the South American adventures of British explorer, cartographer and archaeologist Lt Colonel Percy Fawcett. I joined a panel discussion in London last week, along with historian Dan Snow and Lost City of Z author David Grann, discussing how Percy would have explored and mapped a new land. Catch up on the podcast here.

Dan, David and Mark

A member of the Royal Geographical Society (RGS), Percy Fawcett first arrived in South American in 1906 to survey and map an area of jungle lying on the Brazil and Bolivian border. The border between the two countries was not fully mapped and it was agreed that an RGS survey and map would be accepted as an impartial representation of the border. Today we would complete this activity using satellite systems and sophisticated surveying technology, which obviously wasn’t available back then. So, how would Percy and his team have gone about making maps?

Despite the gulf between today’s technology and that available to Colonel Fawcett the same basic principles for mapping a “blank area” apply. First establish known points of reference and break the area down into manageable sections. The surveyor’s mantra of working “from the whole to the part” applies. Any surveying Percy would have done would have been largely angle based with distances measured using pacing, chains or graduated ropes or even estimated. The starting point would likely have seen him and his colleagues establishing “control points”. These would have been the most accurate positions possible under the conditions and with the available equipment and techniques. These points would be equivalent to our Trigs, which would have allowed him to do rudimentary triangulation – surveying the land by breaking it down into triangles.

To establish a control point, Percy would likely have used observations to stars or sun. Star observations, especially using Polaris (“North Star”) in the northern hemisphere or Crux (“Southern Cross”) in the southern hemisphere can establish a latitude. Sun observations combined with astronomical almanacs can also yield a latitude reading. Longitude can be established by observing the movement of the sun and comparing local time (especially noon) and Greenwich Mean Time assuming a chronometer showing GMT is available. It is also possible to establish longitude from astronomical observations but this is more difficult than the time based method. It is likely that Fawcett’s observing instruments included sextants and compasses alongside the more precise theodolite instrument.

The mapping may have employed techniques such as a compass traverse which would start at a “control point” and then use compass bearing for direction. The length of the traverse legs would likely come from simply estimating the distance travelled. Shorter legs could employ a survey chain or graduated rope to measure the distance. The traverse legs would join significant features (e.g. a prominent river bend or rock outcrop) and detail in between would likely be sketched in. On water a graduated “log line reel”, with on end on the boat and the other fixed to a stationary object, could be used to measure distance travelled and also speed of the current.

It’s hard to imagine the harsh conditions under which the surveying took place and the arduous task that it must have been. However, it is a testament to the determination of Colonel Fawcett and his expedition teams that modern surveys and investigations now suggest that there were indeed many Amazonian settlements that pre-date the arrival of Europeans by several hundred years. The settlement sites include evidence of walls and roads networks and space for thousands of inhabitants. Some of these sites are in same region where Fawcett hoped to find his “Lost City of Z”.

Don’t forget to catch up on the podcast here.

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