Saturday, 30 June 2018

Otago Central Railway [63J]: Ranfurly-Alexandra 10 (Omakau-Lauder 3)

Due to being busy with a few other things there hasn't been much done on the Otago Central rail maps lately. I'm working on Lauder again but the mosaic still needs some work before I can actually use it. The interim version of Lauder is below.

As you can see there is improved image quality in this 1965 aerial photo which has been the main goal of reworking the aerial mosaics.

But as I noted above this mosaic has to be done again because of misalignment of the tracks. There is always going to be some kind of alignment issue because of the inherent nature of aerial photography, but the tracks on the ground have to line up, because flat features on the ground over a short distance with minimal altitude change are the least affected by variances in un-orthorectified imagery, and so it's reasonable to use these features as the alignment baseline.

As a result I need a few hours (probably early next week) to correct the mosaic and then bring in new map tiles to the GIS, realign the map features, and then produce the final versions of the maps. So there will be one more post about Lauder when those maps are completed.

And then the next station to be looked at is Auripo. It will be interesting to see if LGGA have scanned the only available survey of a good resolution, Survey 112, yet. If they haven't, I have some ANZ track diagrams I can put into a mosaic to trace off, and then some other low resolution aerials to use in the mosaics for the final maps.