Monday, 17 December 2018

Palmerston North Gisborne Line [0C]: PNGL maps update project [3]

The most complex task of assembling a collection of aerial photography to support a NZ Rail Maps project is almost complete. This one is extremely complex because it has been necessary to access multiple generations of base aerial photography for the same location, simply because after six years of closure much of the current aerials make it difficult to pick out much detail on the ground in places. 

As well, there is higher resolution coverage of Napier, Gisborne and a few smaller locations along the way. Having discovered the 0.15 metre coverage of Gisborne in particular means I have to redo the mosaics for Gisborne City with the larger scale stuff, but it will be worth it to be able to pick out and display more detail on the ground, because these aerials also date from when the line was open.

What makes getting the Linz base aerial photography together tedious is their limit of 3.5 GB for a free download. The workaround is to pay hundreds of dollars to have the stuff shipped out on a pen drive. So of course I have to split each source layer into multiple downloads of around 3.5 GB (sometimes they are actually larger, as much as 1 GB greater) and then reassemble them. And because I can only draw a rectangle on the screen to select the area I want, I then have to go through the downloaded tiles and select only the ones I need to cover the railway corridor. This is done in part using a script that reads a layer list and then copies just the files needed.

So all those tasks added together makes a lot of work to get what we need together, for just 200 km of track length. So far I have only done the full base aerial imagery for a small number of volumes. The aerial photos and mosaics do take up a lot of disk space on my computer and both are due for a cleanout to free up some disk space.

Saturday, 15 December 2018

Palmerston North Gisborne Line [0B]: PNGL maps update project [2]

The PNGL map revision project is currently making good progress and has been the subject of a lot of work over the past few days.

I am now in the process of downloading the base aerial photography for the entire route from Napier to Gisborne. This will be followed at a later date by obtaining the same imagery for Palmerston North to Napier so that the entirety of Volume 5 can be completed and put into a PDF, as well as the other formats.

As it turns out, there is historical aerial imagery of just about every station along the route, so I expect to be able to add full station layouts all the way through.

This kind of detailing is not something I will do for every line, but it is a kind of goal to be able to do this as much as possible, without it consuming so much time that it takes forever to complete map revisions. With the additional resources I now have at my disposal I expect to be able to speed up some of the mosaic production and therefore push things along a bit more.

The overall timeframe is subservient to the Otago Central one, however I expect by the end of this year I will have all the aerial imagery I need (including mosaics) and be working on the maps on a regular basis. Once the mosaics etc are completed then drawing layouts off them is relatively quick and easy.

After NGL it is PNL and then the Moutohora and Ngatapa lines will have to be added for a complete Volume 5 and that will take a fair chunk of 2019 I would think. 

But I definitely hope to get Volume 12 complete right alongside Volume 5 and there is a lot of Volume 12 work also to be completed so let's say I plan on both volumes completed within the next 12 months.

Beach Loop 1986 in the first photo, and in the second, last year.


Friday, 14 December 2018

Otago Central Railway [64C]: Middlemarch-Ranfurly 3 - Ranfurly 1

Ranfurly using the 1973 aerial survey as a background. Ranfurly is a nice little railway precinct with virtually all the buildings intact except for the first goods shed and the first engine shed, and is a complete contrast to Alexandra where only the station platform remains.

At the moment I am busy downloading all the base aerial photography for Napier-Gisborne which is slowing down Volume 12 stuff a bit but it is coming together and I will be revising some more of the Central stuff over the weekend.