MSL Rolleston-Timaru [0A]: Intro 1

With this particular article I am making it clear I am working towards Volume 11 as a major effort to get something that is actually going to be completed as a volume as soon as possible. This will not be a continuous effort throughout the year but it will be a major focus for the maps this year. At the same time I am refocusing my ambitious schedule that was planned for the year and suggesting it might have to be put out over two or three years.
Rolleston all the way through to Timaru is covered by a 0.3 metre aerial layer. At the moment I am downloading all of what is available in that layer for MSL right down to Waikouaiti and then from there all the way down to Dunedin and then Invercargill will soon follow. Mosaic projects have been assembled over the past few days to cover Lyttelton through to Templeton (the limit of 0.075 metre coverage of Christchurch), and from there will cover Rolleston and any other townships that are in 0.125 metre coverage for the Selwyn District, and from there at 0.3 metres heading south.
We will be using all available NZR surveys for the stations heading south and to match this resolution the 0.3 metre images will have to be rescaled to 0.1 metre size and segmented mosaic canvas used. Last time I wrote about using linear and segmented mosaic projects and indicated a clear preference for linear. However this is only possible where the base imagery is no more than 0.125 m pixel size as too much detail is lost scaling down the NZR images to match larger pixel sizes. At that point I have to bring in a tile grid to sit in the background of the canvas to provide grid indexes for segments and we don’t want to duplicate multiple copies of this grid across a linear canvas because there are too many additional layers. Segmenting is actually OK for this situation because the stations are quite a distance apart, meaning no overlap problems, and therefore there is no benefit to a linear canvas.
So I am just about to create the first segmented canvas mosaic project in Gimp for Weedons / Weedons AFB / Burnham and maybe a few other stations heading south as well.
As one can imagine, completing a volume for a line as long as the MSL is quite an ambitious undertaking and it will be staged out and I will take breaks to do work on other areas as I always do. Volumes 5 and 12 in particular are other areas I want to make significant progress on this year and as previously noted there is the schedule I talked about earlier this year and I will look at the standard of completion for other volumes. But to get any of these volumes together I have to download all the aerial imagery for the base maps and that is always a big effort and that at the minimum is what is needed to bring the maps together regardless of what level is produced.
MSL also incorporates previous work done with Methven and Springburn lines and this will be brought in as well. There are no NZR surveys for either line so no issue with having to match NZR survey resolution.