Otago Central Railway [61S]: Alexandra-Cromwell 16

So the Cromwell maps took a little longer because I had to make bridge tiles to bridge the gap between the new aerial imagery and the old stuff I have for the rest of the gorge. So that there is a fairly seamless join between the new tiles and the existing ones. The bridge tiles are a regular 9600 pixel width (LINZ’s 4800 width tiles doubled in each direction) but a special height of 9599 pixels to line up with the existing tiles, and why this odd size? Well, the existing tiles are funny hybrid ones which were originally 0.75 metres resolution and I found some way of scaling 0.4 metre tiles to overlay on them to update the base imagery to a higher resolution without having to redo everything from scratch. And because of that the 0.4 metre tiles don’t line up perfectly with them when you mix 0.4 metre and 0.75 metre derived tiles in the same map. So the bridge tiles have had to be cropped to a specific size that will fit exactly in the gap and part of that was to overlay another 1965 aerial photo over the old 1962 ones and make it line up almost perfectly at the join.
So here are the completed maps for Cromwell. The next stage is Clyde which will be started today, and then Alexandra which will include the aerial photo for the Fulton Hogan siding. At the same time I am working on the head of the lake mosaics as there is enough imagery to get to Lowburn for a start (another drowned bridge there) and hopefully there will be enough good stuff to get all the way up to Mount Pisa where the lake turns back into a river.
I still have to muck around with the masking and the lake and riverbed layers to get them the same as what I did with the older aerial photography. I also got a low res 1958 layer to give me the position of the original goods shed.