Tuesday, 26 May 2015

Mapping the Cromwell Gorge prior to the Clyde Dam

I am currently investigating options for aerial photography. At the moment it appears this will not be cheap. To obtain the NZAM prints for the route taken in 1962 will require the following images:

  • Survey 1452
    • Run T
      • Photos 1,4,7,10,13,16
    • Run U
      • Photos 7,10
    • Run V
      • Photos 5,7,9

That’s a total of 11 prints. The cheapest available option, so far, is $940 if they are all purchased at the same time. But if I was to proceed it would be much more likely to split these across at least three orders, which will be somewhat more expensive overall.

The first question is simply whether the cheapest per-print option (contact print) is going to be of a high enough resolution to serve my purpose. The original scale is 1:8800. At that resolution, provided the print is sharp and clear, it would certainly be possible to pick out roads and railways. Whether there is enough detail to resolve individual tracks in a yard is a more serious question.

The other option is to go for surveys that were taken at a smaller scale, for example the 1965 or 1968 surveys taken at 1:11000 and 1:16000 respectively, and have the digital scan option which gets around the need to produce a print, but then there is still the question of resolution. At 1:16000 there would only need to be half the number of images, but the cost if obtained scanned would be much the same because the scanning price is about double at the quantity involved.

In terms of the overall picture of aerial photography use – outside the Otago Central line I wouldn’t expect to make much use of aerial photography, although that is realistic in any case because I wouldn’t have time to draw everything that would be available from the use of aerial photography. There is simply not the interest from me to want to produce the maps for every railway station in the country. It is really only the OCR I am interested in.

I am still making enquiries so I do not know if this proposal for mapping the Cromwell Gorge will proceed in its current form. It would be nice if Otago Regional Council had a site like Canterbury Maps. I have discovered that Archives New Zealand also hold prints of some of the surveys so the next step will be to enquire in relation to their holdings in Wellington.