Otago Central Railway [61N]: Cromwell-Alexandra 11

I'm just opening this post with a note about the recently completed and published article series about the Otago Central Railway. There were some issues with editorial changes to the last part of the article. These are being addressed with a Research Note and a Letter to the Editor that will be published in a future edition of the NZ Railway Observer. Hopefully this will go some way to reconciling some of the issues related to the differences in use of imperial and metric distance measurements which have been highlighted in the above article series.

Work today is continuing to update the aerial footage from Cromwell to Clyde to the 0.4 metre higher resolution photography from Linz replacing the 0.75 metre photography that I originally used to do the aerial photos for the gorge. At the moment I am rendering the 0.75 metre intermediate tiles which consist of the lower resolution tiles with the higher resolution stuff overlaid on top of them. Once these tiles have been rendered they can be imported back into Gimp, after which the next stage is to copy the masks from the original plain tiles to the composites, and as they occupy exactly the same area this is a very straightforward 1:1 copy and paste of the masks.

Then once that has been completed then the final mosaic tiles, consisting of a mixture of 0.75 metre, 0.4 metre and historic aerial photography, are rendered to be loaded into Qgis as the the aerial photography backgrounds for this part of the maps. The overlaying of the 0.4 metre tiles over the 0.75 metre tiles went very smoothly and routinely. Once the first tile in the upper left corner (Cromwell township) was correctly positioned, all of the other tiles were anchored in position relative to this tile and all of the tiles were in perfect alignment at all times to the 0.75 metre tiles, as noted repeatedly when each new 0.4 metre tile was scaled down and positioned. The net result will be a higher quality background for the maps as the 0.4 metre coverage is much sharper and clearer as well as having more accurate colours (at least that's what I assume).

Because the intermediate rendering of the composite tiles prior to masking is as usual a slow process with Gimp, I am simultaneously using a second computer to update the maps in Alexandra in particular so that they are completed at the same time so hopefully I can start rendering out the maps in the next few days and sign off this section of the line as completed. As it can be noted that doing these historical aerial photos for the Cromwell Gorge section of the maps has been the most time consuming part of the whole project with a lot of different steps involved. 

This image shows the Alexandra rail yard at Chicago St crossing using the 1965 aerial photo layer background. Qgis 2.18.18 is running in a virtual machine with the guest OS being Debian 9.4 running LXQT. Whilst I have lots of VMs running 2.18 this one happens to be the best functioning one right now.

Main North Line [11F]: Addington 6; Otago Central Railway [62B]: Km Pegs 2

So Addington is being more or less recreated from scratch. Doing the adjustment in the middle part (Addington North as it is called in my computer) covering the Main North Line going north to Riccarton was actually relatively quick and easy to fix, as with all the linked layers, moving one moved all the others, and no scaling was needed as the amount of movement needed was relatively small. The problem is, the other two extremities going east and west on the MSL have to, in effect, be hung on each side, as everything has to line up and be as smooth as possible joining up on the edges. So I have been working since then on the western side, starting with the middle part and adding things onto the left hand side of it, the base imagery and followed by the aerials that are needed to do this. 

The first aerial, 2345-B-3, is actually needed for the middle part at the extreme left hand edge, just a little tiny sliver on the side of 2345-B-5 because it doesn't quite reach the boundary of the geojpeg for that part. The rest of B-3 will make up the West project, as soon as I finish getting it set up for the North part, I then save the North project as West and then add in the rest of the stuff for West. It takes time because even on my main computer with 24 GB of RAM, these are big files for Gimp to handle, and so moving stuff around is slow work. The biggest advantage has been to be able to copy in layers from the previous versions of Gimp projects which saves a lot of time rescaling and rotating the layers from scratch. So it will come together a lot quicker than the projects last week, and I can use my second computer with 16 GB of RAM to do the rendering at the same time as working on the main computer to move the layers around. But it will still take until sometime next week to have it all back together again.

The rest of today has been working out the issues with the published articles in the NZ Railway Observer to write a complete list of them, which is currently being assembled as another post, and to inform the actual letter that will be sent to the the editor of NZRO; and doing a km peg list for the rail trail, using their street view imagery and marking the pegs on a Google MyMap. Right now I have discovered two 70 km pegs at Ngapuna. This raises the question that the rail trail trust has been putting in missing pegs and if so how accurate can they be assumed to be. The reason for doing these km pegs on a map is mainly to inform the discussion about the editing of my articles in NZRO. It does look like the rail trail trust could be taking pegs out and putting them in because I have not yet found one single half kilometre peg anywhere along the trail to date, but in a few locations I have spotted half km pegs with numbers attached to them. If the rail trail trust are putting in pegs the question is just how accurate their measurements are and perhaps they would like to explain the two pegs at Ngapuna.

Letter to the Editor of the New Zealand Railway Observer

Concerning editorial changes made to submitted articles to the New Zealand Railway Observer.

During the last three editions of the New Zealand Railway Observer (No.346-348) I have had published a series of articles entitled "The Geography of the Otago Central Railway". I enjoyed writing these articles and sought in the process of this to provide another look at this railway line and the present day relevance of it. The research behind these articles has been a part of the NZ Rail Maps project, and the maps produced by this project are a key part of the information process that has been used to produce the article series.

I regret however that I must put on record at this point my concern at certain editorial changes that were made to these articles after they were submitted for publication. These changes were made without consultation with me, and in the main are preoccupied with an obvious editorial prejudice against imperial measurements of distance such as miles. There is no legal requirement to use metric measurements of distance in the context of publications such as these, and overzealous conversion of imperial measurements results in many absurdities in written work that I have read from a variety of authors and publishers over many years. In this case the simple metrication of imperial distances fails to understand the historical differences between these measurements as they were used on the railway system of New Zealand.

The articles which I submitted used metric measurements where appropriate, and imperial measurements where appropriate. The following are the key objections I have to the metrication of the entire article:

1. It is impossible to describe a milepost as a "1.6 km post". There is no such thing as a physical post that was put into the ground alongside a railway at 1.6 km intervals. Thus, the line of my article reading for example "Between 38 and 39 miles" which has been changed into "Between 59 and 62 km" refers to actual different locations than the 38 and 39 mile pegs. I can't quite make up my mind whether "59 to 62 km" is better than the direct equivalents of 61.14 and 62.75 km which some publications would have used. Note that "59 to 62 km" in the above appear to be factually wrong. This makes about as much sense as changing the names of official publications that have "1 mile" or similar in their title.

2. The measurements of mileposts and kilometre posts were done at different times, and in the cases of many railway lines, measured actual different distances. These changes have occurred because many railway lines have been deviated or realigned. Historically when deviations or realignments have been made, the original mile or km posts do not get relocated to reflect the change in distance. Instead the engineers have historically made use of a device called a "short" or a "long" mile [1].  For many lines in NZ, "short" and "long" miles persisted until such a time as metrication in 1974 when the lines were remeasured from scratch and the kilometre and half-kilometre pegs put in. It therefore cannot be assumed that distances measured in kilometres will always correspond exactly to distances measured in miles on the same line.

3. The distances shown in the article are official distances from official NZR and its successors' publications. Chiefly these publications are the Working Timetable, and lesser publications include the chainage books which are held by Archives New Zealand. The first metric WT for the Otago Central Railway omitted distances for stations which had closed. For these stations, therefore, the only available and appropriate official distance measurement is the one from a preceding WT measured in miles and chains. Chainage books are all in miles and chains and all distances derived from them have appropriately been expressed in decimal miles. 

Researchers in this area who have made use of the New Zealand Railway and Tramway Atlas, a popular publication which includes distance measurements for the vast majority of railway stations across New Zealand, are aware of discrepancies between these measurements and those found in many of the metric era Working Timetables. We can only assume that the publishers chose to hand convert the imperial distances to metric rather than obtaining new measurements from the metric WTs. For the same reason I have not used the metric distances shown in other publications about the Otago Central Railway for station locations that are not shown in the metric WT. 

4. The maps drawn of the line are marked using the imperial mileposts obtained from chainage charts and in many cases measured from easily verifiable geographical locations shown in the same charts. Whilst there may be some minor discrepancies in actual milepost positions, these measurements offer a reasonable degree of accuracy in the placement of the mileposts on physical positions on the map. The same information is not available for most kilometre posts on the line, a number of which have been removed from the line in any case. Those metric measurements shown are mostly station locations that are in the metric WT. The measurements on the map are those which can be obtained from official railway publications according to the preceding principles and quoting a measurement that has been converted makes no sense in this context because there won't be a corresponding measurement marked on the map itself. 

Reference: [1] NZR DEO’s Office (c.1930-c.1956). Chainage O C B [Otago Central Branch] 0 Miles 00 Chains to 25 Miles 60 Chains. Archives New Zealand, R18524763.