Wairarapa Line [0CC]: Volume 6 Progress Update 29

Good evening. Work is continuing at a steady pace on Volume 6 with the alignment of our maps to the current base imagery reaching down to the 119 km peg just south of Eketahuna at present. This has slowed a little due to some work on another volume but is still continuing and we expect some more progress over the next couple of days.

After another 12 GB download from the LDS site we are getting the rest of the tiles together to complete the mosaics for everything we are covering north of Featherston, the locations being the ones outlined in our previous post. There could still be one or two additional stations added in.

Also welcome to everyone who reads these posts via our Facebook page. We regret that due to a Facebook issue about a month's worth of posts haven't been syndicated onto the page. These posts are all in the blog and can be read by browsing it directly. This is obviously more important with the cessation of our Facebook group in that everyone using Facebook has to read the page, and we trust the feed will resume with this post.

As you know, this project in the Intermediate and Comprehensive levels of maps makes heavy use of Retrolens as a source for these historical aerial images. Whilst we are big fans of the site and have made lots of maps with their images, one annoyance is that it is impossible to find any way to contact them in order to resolve any issues with the site. As noted with Survey 570 the only resolution is to get hold of the original scans from Linz. However there is considerable inconvenience in this as found with 570.

Wairarapa Line [0R]: Volume 6 Progress Update 18

Good day to our readers. This update is quite soon after the last one but that one was so delayed waiting for us to put in maps of Silverstream that we just sent it out incomplete. We do now have these maps and some examples are below.

A key focus for this update has been a schedule revision as work has slowed a lot over the past few days, but is going to pick up again. We are now looking at a more realistic schedule for completing the work to Masterton, and we expect that could be one week but quite possibly two. The base maps are completed to Upper Hutt at this stage but the historical maps will include several sidings at Trentham that previously existed. Because we have already mapped Upper Hutt there is no additional work needed. Beyond Upper Hutt we will be relying on previous work done on this section and only limited revision will be needed until we get to Featherston and have aerial photos available of the three station yards. Beyond Masterton we are just using the base imagery and not planning to add any aerial coverage, and Woodville is already well covered.

So it is possible now a more realistic completion could be somewhere around the 10th of April, one month later than originally planned. The reason why the schedule has slipped so much is we have not taken into account the large amount of detail in the Wellington suburban area and the time it takes to research it and add it to maps. However as there are only four urban areas of similar size in NZ it does not follow that every volume of maps is going to be slowed down the same amount, but it does follow that the schedule overall is probably going to slip a bit more. It is hard to say at this stage whether two years might be a more realistic prospect. We are quite certain now that the full 12 volumes of maps will not be completed to the original schedule of 12 months but we still think we may get 9 or 10 volumes completed in 2020 and possibly just volume 2 and 12 would be pushed into 2021, since so much work has been already done on some of the volumes.

Some other news is we can get survey 570 taken up the Hutt Valley in 1951 directly from Linz although at the moment there might be a delay. If there is a delay, it's possible we may push on to the expected completion timeframe and re-publish affected maps once we can get those aerial photos, which cover the Western Hutt section, Silver Stream, Upper Hutt to Mangaroa and one or two other interesting places. The scale is at 1:7000 which especially for Western Hutt would be really useful as what we have at the moment in the area taken in 1939 would have been good but most of it is in shadow.

 

Another useful resource to date has been the Valley Signals site and we have since obtained further resources from the webmaster of that site. We are being choosy about whether to incorporate any of those into mosaics, which is time consuming, or just transcribing information. Nevertheless there is additional valuable information therein that will fill in a few gaps here and there. We will also soon have access to a North Island working timetable but this will mainly inform more recent history and probably that will mainly affect the line north of Featherston where we are not doing anything in depth like we have in urban Wellington/Hutt.

1945 aerial view of Silverstream Bridge going across into the siding on the south side where the hospital was.

Silverstream Bridge Siding as in 1945. This is currently the site of McKirdy Station on the Silver Stream Railway and some of the markings shown on the map such as the turntable, engine shed and station building are related to that. There appears to have been no passenger station there, only what looks like a goods loading shelter over the siding. The siding itself was just alongside the main line and did not run into the hospital site as we had earlier thought.

A 1970 map showing the site of both Silverstream stations.  Work was then underway to build an underpass at Field Street and the site of the two railway bridges with the rail tracks diverted around them can be seen.

This diagram corresponds to the previous aerial map.

Palmerston North Gisborne Line [0Q]: Volume 5 Progress Update 17

After our last post about extra work being discovered as we got into more depth of working on lines in the Gisborne area, that trend has continued today. Whilst in the course of tidying up all the aerial photography around the Gisborne area and labelling many of the sidings off the main line, we discovered a second NZR aerial survey for Gisborne Station.

To explain this in more depth, Retrolens has many different survey sources, most of them various government departments. The ones that have consistently proved most useful for NZ Rail Maps are the highway surveys done by the Roads Board et al (where these highways are close to railway lines) and the ones that NZR themselves had done. Most of these are around 1:8000 in scale. Indeed, the aerial survey we used to map the Cromwell Gorge section of the OCB for Volume 12, dating from 1962, is a highway survey (SH8), as were some other historical surveys of the railway around the Clutha Valley.

NZR aerial surveys mainly take two forms. Major stations had their own surveys, which are generally carried out at a scale of about 1:4300, though there are a small number at a larger scale. Often there will be just one run (Run A), but occasionally with a big area, for example the Port of Lyttelton, with changes in direction, there can be several runs to get everything covered.

In addition, major rail corridors had corridor surveys, which are generally at a scale of 1:5500. They cover a whole corridor or part corridor using multiple runs because of the fact that no corridor runs in a straight line, but the aerial survey aircraft must fly in a straight line for each run. There are no corridor surveys for less important lines like the Hokitika/Ross branch, Otago Central Branch, Kingston Branch etc. They just cover the major corridors, which includes the Palmerston North Gisborne Line in this instance - the corridor survey around Gisborne was done in 1986 and happens to include the Makaraka Branch in the last run into Gisborne Station.

Going back to the station surveys, some stations had more than one done. When we first came to do Gisborne Station in 2018, the survey we found at that time was dated 1968. We do not recall if the 1982 survey was found at that time, but the 1968 one was chosen. Having done more investigation today into the area around Gisborne Station and the various private sidings, we are now creating map tiles for that era in Gisborne, which will add another era to the historical aerial maps, as well as giving more detail to add to the diagrams.

Today we also finished drawing the yard layout for Matawhero. This means the next part of the M-M-M series can be written tomorrow. Whilst looking in the area, we removed Gisborne Aerodrome as a station. This is shown in the Quail Atlas 4th edition, but Dates And Names suggests that it was for a siding that was never installed, so it never existed. We are fairly confident of having got everything we need for Gisborne now, and so there is just Muriwai Station to complete mapping the area and allow us to push on back towards Napier and points further south in finalising the maps to be completed next week.

NZ Rail Maps Project Development Report [2020B]

This report as always with these reports is a general overview of the project as a whole across all volumes. Our earlier report 2020A was written on the first day of the year and outlined our expected programme for map development across the whole project this year.

At present with the development of the maps across all volumes, the following sequence is proposed at this time, but could change later:

• Volume 5 (PNGL) - on track to be completed by the end of January
• Volume 6 (WL) - February
• Volume 4 (MNPL) - March
• Volume 3 (ECMT) - Apri
• Volume 1 (NAL) - May
• Volume 2 (NIMT) - June

This means we have priorisitised the 6 volumes of the North Island for the first half of the year, leaving the 6 volumes of the South Island for the second half of the year. Most of these volumes are already completed to some extent from previous work. The largest amount of work is likely to be needed in the two longest corridors apart from PNGL - these are ECMT and NIMT of course. NIMT is one of the more challenging ones because of the length of the corridor and the fact it runs between two of our largest cities.

We now turn to a look at some evolving changes in the way certain technical aspects of the maps themselves have been developed. What is becoming more commonplace in the maps in general in the last year or two is widespread use of aerial photography to provide references for historical and contemporary content. How that aerial photography is used to provide finished maps has varied to date. Now that we are moving towards completed volumes for all areas, this is very relevant.

Map data in a GIS is handled in layers. Each layer manages a particular type of object and generally for convenience we can further divide the types of data into our own personal classifications. Here are some examples:

• Locations (stations, distance pegs etc)
• Bridges and Tunnels
• Features (such as premises that contain sidings)
• Main Line Corridor(s)
• Branch Line Corridor(s) 
• Yards and Sidings
• Buildings
• Structures
• Sites
• Roads
• Land
• Water
• Terrain
• Aerial Photos

All of the map volume GIS projects follow that general style.

The maps are presented in two overall types. Diagram maps are drawn against a terrain background. The terrain is rendered greyscale relief imagery that shows the type of terrain for the area (i.e. flat or hills). It does not have a significant visual impact upon the finished maps as most of the grey shades are less than 50% density.

Aerial maps are drawn against an aerial photography background. With this type of background there are many more challenges mostly in making data layers stand out against a background that is much more dense and often quite dark. There is also the issue of the data layers obscuring visible content in the aerial photography itself. Another issue is the alignment of some of the general (non rail) data layers such as roads.

Because of these issues with aerial photography in particular, the work on Volume 5 has begun to classify layers as being diagram specific. This means when we produce a map of one particular area, such as one station, a diagram map will show much more data than an aerial map. This means the aerial map will be visually a lot less cluttered and more of the aerial background will be visible.

Another important aspect specifically relating to diagrams has been the production of diagrams that cover more than one historical era. We developed a system a year or two back using date range fields to enable us to determine where possible when a particular object became visible and when it became invisible, driven by aerial photography reference. By applying filter formulas, we could cause these objects to appear and disappear on the resulting maps. The main drawback however is the amount of work needed to create these different historical eras. In major yards a lot of changes can take place over a long period.

It has been decided that most diagrams going forward will be composites that show multiple eras in one diagram, with labelling to clarify certain aspects. Eras will be solely represented by producing an aerial map for each era, but as the map information on an aerial map is not the full range of data visible on a diagram map, much of the information that is era specific will not be marked on the aerial map itself. Instead, a reader will use the diagram map to cross reference specific features which are visible on an aerial map.

A small change has also occurred where aerial photo tiles are partly filled by empty canvas in the graphics editing software that produces (mainly) historical tiles, but also is used to remove some black edges that we get in the tiles we download from Linz. For some time we have filled these gaps with current aerial photos. However, to avoid confusing different eras of aerial photography, starting with Volume 5 we will fill these gaps with a white background.

We are also moving towards producing combined map sets that incorporate all aerial and diagram maps together in sequence. This is in addition to producing separate aerial and diagram sets, which has been the norm up until now.

Otago Central Railway [64A]: Middlemarch-Ranfurly 1 / OCR Maps From Here

This isn't a new series as such but it is about adding to the work already done in this sector of mapping the OCR. Yesterday I had a look for new Retrolens aerial photo content for the stations in the Ida Valley area and have obtained a significant amount from recent RL additions. I then decided to have a look for content further down the line as I did not have any good aerials of a number of locations. This was summed up in detail in this post I did last December. It basically has said that coverage not yet available at that time could include the following areas (updated to those areas I haven't yet mapped or finished):

• Auripo
• Survey 112 of 1939 which is now available. The only higher res coverage for when it was open.
• Ida Valley
• Survey 112 of 1939 now available. Again the only higher res coverage for when it was open.
• Ranfurly
• Survey 890 (1956), 1745 (1965) and 5800 (1980) should cover well. 890 in particular is important as it gives the best early coverage which probably will show the old locomotive depot and turntable at the north end. As far as I can tell none of these are available yet. Survey 112 goes close to Ranfurly but not actually over it.
• Survey 2590 is available. This looks like it is an official NZR survey as it only covers the railway yard. Taken in 1973 it will let me publish full aerial maps of Ranfurly.
• Waipiata
• Survey 2833 is the only really good coverage of Waipiata. Again it appears to be the official NZR survey that was taken in 1975. This is good as there is really nothing else suitable for Waipiata. NZR must have had reasonable confidence these two stations would be staying open to have these surveys done as there are not these surveys in existence for every station.
• Hyde
• The ballast pit when the siding was opened is not covered in anything I can find. I have found lower res images from 1959 and 1960 (Surveys 1053 and 1214) which were 7-8 years after the siding was removed. It does give a clue as to what the pit looked like in that era (it was kept open without a siding because NZR used trucks to bring ballast to the Hyde yard to be loaded there). So it should be possible with that to estimate where the siding ran, which will be marked as "uncertain route". I do have some data for the siding that should help with the route, but not an actual map. 
• Pukerangi-Taioma
• There is some 1940s coverage now available which should be reasonably sharp but is actually not too good (I don't know whether it was a bright day or if the scanner overexposed the scans as they are a bit washed out). I will see if that coverage is useful.
• In many cases I have now obtained station diagrams from Archives Dunedin.
• Wingatui-Taioma
• I have some Dunedin City aerial photos and a bit of Retrolens stuff. I am unclear how useful that stuff is.
• I have also obtained station diagrams.

So there we have it. The original post linked above also had diagrams taken from the aerial footprints layer to show coverage through the decades. It is interesting to view those diagrams in relation to the map of the line. 

At the moment I am updating the maps of the Ida Valley stations (Auripo, Ida Valley and Oturehua) through the new coverage that has just been obtained. Here is a description of the remaining sections to be mapped:

• From the Ida Valley the route goes through the gap between Rough Ridge and the Idaburn Hills down into the White Sow Valley, and then through another gap at the north end of Little Rough Ridge to Wedderburn. Essentially we call this the "Wedderburn Summit" or "Wedderburn Pass".
• From Wedderburn down to Ranfurly and Waipiata is in the Maniototo Plain and railway-east of Waipiata the railway follows the narrow valley in the upper reaches of the Taieri River closely until Hyde and then the Strath Taieri through to Middlemarch. 
• Railway-east of Middlemarch the line gradually closes in on the Taieri River valley, finally entering the gorge east of Pukerangi and eventually exiting at Taioma, descending through the hills until it enters the Taieri Plain at Wairongoa. 
• The last few kilometres is across the relatively flat Taieri Plain to Wingatui.

The names of the stations, with the probability of maps (High, Low or Nil), are:

• Auripo - H
• Ida Valley - H
• Oturehua - H
• Wedderburn - H
• Ranfurly - H
• Waipiata - H
• Taieri Lake Siding - N
• Kokonga - H
• Tiroiti - H
• Hyde / Hyde Township / Hyde Ballast Pit - H/H/H
• Rock and Pillar - H
• Ngapuna - H
• Middlemarch - H
• Sutton - H
• Matarae / Matarae Siding - L/L
• Pukerangi - H
• The Reefs / Quartz Reef Siding - L/L
• Flat Stream - L
• Deep Stream - L
• Hindon - H
• Christmas Creek - L
• Mt Allan / Little Mt Allan - H/L
• Parera - H
• Taioma - L
• Salisbury - H
• Wairongoa - L
• North Taieri / Tanks - H/L
• Taieri Aerodrome / Estate - H
• Wingatui - H

These probability scores reflect the availability of suitable aerial coverage or diagrams. For something that has an L score, you will most likely only see the station site marked but not any other detail. In some cases there was nothing at a specific location, it was just a stop on the main line with no infrastructure. In other cases I can't get a diagram or aerial photo. So North Taieri Tanks is just going be marked because there was never a siding, Machine Creek which isn't in the above list and the water tanks at Prices Creek, Mt Allan water tanks, Little Mt Allan halt with no siding or shed and the like will just be marked as a point on the line. 

As far as miscellaneous sidings go like ballast sidings that are on the chainage charts, the points and direction will be marked (and the length if known) but not the actual route because that often isn't clear. Ida Valley pit doesn't have a siding marked but the water tanks and coaling facility are marked. There are a lot of little details like that that will be marked wherever possible but not with much clarity because that's just the way it is.

There is still a lot of work to do with the maps and I expect this to continue into next year and it is hard to say how long it will all take but I can't see it taking more than 12 months but I am not really sure how long is needed.

The subsequent posts to this one will finish the 63 Ranfurly-Alexandra series so it will be a while before you see [64B] and subsequent posts in the 64 series for Middlemarch-Ranfurly.

Otago Central Railway [53]: Aerial coverage from future Retrolens

As we know, to be able to draw my maps, I have made extensive use of aerial photography. Retrolens is where most of this is coming from these days as I have wound down getting contact prints scanned from Archives NZ to reduce cost.

There are a few areas I have not yet got coverage for because they are still being scanned. Here are some illustrations of why that is.

This is how much of the line was covered by imagery with a scale of less than 1:12000 in the 1930s. In short, nowhere near as much as I would have liked.

1940s large scale coverage.

1950s hi res coverage is mostly along SH85.

1960s hi res coverage is mostly SH8, SH85, SH87 and the Clyde hydro development. Covers a fair amount but there are obvious gaps.

At least for the 1970s we can get some of Ranfurly and Waipiata that isn't covered much in the other surveys, and the Clyde hydro area is well covered as well.

For the 1980s it's pretty much SH85 and SH87 again. 

This reality means there are some unavoidable black spots for coverage. Here are the challenged areas in particular:

• Galloway: Officially, there is no large scale coverage of this station. Unofficially, due to survey drift, there may actually be some inclusion in survey 5800 of 1980, but the station actually did close in 1978. Hence I have only been able to source small scale so far. This is close enough though.
• Auripo: Survey 112 does cover this area at 1:12000 and dated 1939. This is the only survey during the period that the station was open. At the time of writing survey 112 was not fully scanned.
• Ida Valley: Survey 112 mentioned above is again the only large scale survey for the period that the station was opened. Not yet scanned for the area.
• Ranfurly: There are actually a number of suitable surveys for Ranfurly, just not ones that have been scanned yet, because of it being on SH85. Survey 112 officially doesn't cover the area, but it is possible that with survey drift it will cover the station area. Survey 890 of 1956 and Survey 1745 of 1965 do cover Ranfurly and so it should be possible to see the old loco depot area if the survey boundaries are correct. Surveys 2833 of 1975 and 5800 of 1980 will also be of use once they come online.
• Waipiata: Waipiata is a blackspot because of it being in the middle of a triangle between SH85 and SH87. Still, it should be well covered by Survey 2833, giving us some 1975 era views, when the station was still fully open.
• Hyde Ballast Pit: There isn't any large scale coverage of the area until Survey 1916 of 1966, so there just isn't anything that will show us tracks on the ground in the ballast pit, which closed in 1952. Smaller scale stuff from the mid 1950s isn't able to help much.
• Middlemarch: Survey 1915 of 1966 is the first large scale coverage and has very recently been added to Retrolens. Expect to see a posting about Middlemarch very soon.
• Pukerangi-Taioma: This is understandable black spot territory given the sparse population and distance off SH87 and there is in fact no large scale coverage at all in the Linz database. However, there is coverage of different parts of these areas in different surveys at smaller scales. 
• Taioma-Christmas Creek is covered by Survey 1435 of 1963 at 1:18100, which has not yet been added to Retrolens.
• Christmas Creek-Pukerangi is covered by various surveys around 1:23000 or 1:25000. I have seen some of this coverage and generally it is fairly fuzzy.
• Wingatui - Taioma: Coverage starts from 1949 onwards. At the time of writing not yet in Retrolens. (In reality this will only be Taieri Aerodrome, Salisbury and the 2nd Taioma station of interest)

Looking at the gaps particularly the Taieri Gorge I have had to weigh up the pros and cons of various options for closing those gaps and have decided pretty much to focus on getting the chainage charts copied from Archives New Zealand for the first 25 miles (I already have them for 25 to 146 miles) and waiting for more coverage to come online. The chainage charts should have sufficiently good yard plans for all the Taieri Gorge stations from the first construction of the line and it would take too much time or cost to get plans of these stations from the individual files. In any case actual yard plans often aren't as detailed as the chainage charts with distance markings. So it is likely the full maps will not be completed for the series of articles and updates may well be sent in at later times.

Significant changes in maps unlikely as result of new aerial photography availability

In recent posts I have talked about Retrolens and their new aerial photography. One of my recent posts made the point that I don't expect the work done with the Nelson Section maps to be replicated across all the maps I am drawing.

Whilst the aerial photography has been very useful and I will be posting aerial images on the Flickr site shortly for the Otago Central Railway as well as the remaining ones I have obtained for Nelson, it is correct to say that I don't have time to get aerial photography for every single route I have drawn. Only the Linz aerial footage is being used at a base level to draw the maps, and that is because it is georeferenced, meaning it can be opened as a layer in the GIS and directly traced over. I can download the aerial images for a large section of country at once and simply open them, so it is straightforward enough to obtain and use.

Whilst I have been making significant use of aerial imagery both from Retrolens and earlier sourced scanned imagery from the Linz aerial photography contact prints collection held at Archives New Zealand, this is a time consuming and potentially costly exercise. The imagery isn't orthorectified or georeferenced, meaning Qgis can't simply load it as a layer in the way that for example Google Earth would be able to. Even if I was able to get the Qgis wizard to work in placing the images into a layer (which I haven't as yet), it would still be a time consuming process for each image in turn.

Because of this extra time and money cost to get imagery (even allowing for the fact that Retrolens content is free), it would be too slow to bring in the non-georeferenced content which requires extra steps that have to be taken for every single image. The Linz imagery has the georeferencing already done per tile (image) and loading it is all that has to be done to use it. Being orthorectified also means you don't have the time consuming process of shaping it to fit.

The Otago Central imagery I have which includes some quite sharp hi res images from the 1960s for some of the stations that I didn't have tiles of before, will be used to improve the diagrams I have already drawn for every station that was in the chainage charts. For example, the one of Omakau shows where the old turntable pit was, quite well. So it will be good for doing that. In this case it will mainly be copying rather than tracing. As I already said I won't be drawing any new track diagrams anywhere except where details can be directly traced in Qgis off the Linz imagery. That remains my present policy. Next week I'll be working on the SNL again.