We have decided to push ahead with the MNL corridor LDS images and setting up Gimp mosaic projects as a top priority because of the disk space issue. As mentioned before the downloads for this particular corridor are presently using up lots of disk that we want to recover.
As it turns out we already have most of the base imagery downloaded and selected so most of what has been worked on today has been ascertaining how much Retrolens coverage there is of the Main North Line stations.
NZR had basically two types of aerial surveys done for them: station specific surveys, which are easy to spot because the run number is always A, meaning the survey/run/photo number sequence will usually be XXXX-A-1 through to usually no more than 5, another giveway is the earlier ones always have a scale of 1:4300. The other type of survey done is for a whole route. Generally these were just the main lines and were done in the 1970s. A long corridor like the MNL or MSL will be broken into several surveys that must have been a lot of fun to fly as these long main lines are far from straight so the plane would have made many passes to capture all the different runs that make up each survey.
North of Christchurch there are relatively few station surveys as they are generally only for the major stations such as Belfast, Rangiora, Amberley and Waipara. However for many of the other stations, the route surveys done in 1976/77 often are showing the many small stations that were still open at that time (surprising great number as many are long gone these days). We intend to incorporate these into mosaics later on but for the present we are only setting up mosaic projects rather than actually making mosaics. Deviations and realignments also provide reasons for mosaic making.
The only completed set of mosaics north of Rangiora to date are the ones for Amberley, Waipara, Hundalee, and former Tunnel 4 near Oaro. As was mentioned before, we did Picton under a different system some time back. These will be redone under the current system. A couple of stations on the Waiau Branch have also been mosaiced and the rest that we have coverage for can also be done in the future.
Between Parnassus and Wharanui the base coverage we have at the moment is the Kaikoura earthquake coverage shot just after the 2016 Rotherham quake. We are currently considering whether it is suitable to use as a background for the maps. At the moment that is what we are using, but if we decide it isn’t suitable, there will be a lot of work to download the previous base images and they are not as sharp as the EQ stuff, which is at 0.2 metre pixel size.