Good day and welcome to our third project development report for 2021. As the text below documents, project progress is being made on the Main North Line maps. The overall project since completing the first stage of the webmaps last month has shifted towards completing maps in various areas so that the webmaps can be updated, as well as developing the Volumes and Stations websites.

The value of the Retrolens site to this project has resulted in a great deal more detail being able to be added to the maps and the impact of this cannot be underestimated as many more stations are now being documented to a fuller extent as well as other changes on the railway network that can be observed taking place over the past 80 years approximately since the aerial photo surveys first began. The detail of the Main North Line below illustrates this.

Currently the maps are progressing well of the Main North Line with particular focus on Wharanui to Picton, the area historically known as the Picton Section. The Main North Line like many main line corridors was constructed in a number of simultaneous stages from the northern terminus Picton heading south and from the southern terminus Christchurch heading north. These efforts continued through relatively easy country in both cases until the Picton Section was completed at Wharanui in 1915 whilst the Cheviot Branch was completed at Parnassus in 1912. These then became the respective railheads of the sections. At that point there remained only 123 km to complete the full corridor but difficulty was experienced in finding a suitable route through very rugged and often unstable country and various investigations were made during the gap period. The Great Depression brought most railway construction in NZ to a halt for a number of years and it was not until the mid 1930s that work was finally resumed. This resulted in the southern railhead being advanced to Hundalee in 1939 and the northern railhead moving south to Clarence in 1942 and Kaikoura in 1944. The last section, the 39 km from Kaikoura south to Hundalee, was finally completed in time for the official opening in 1945.

In the 76 years since the full completion of the Main North Line many improvements have been made and these are being documented as far as possible in the project which is including the locations of all known stations and maps of a majority of them. Where a map has not been produced of a station, aerial photos will be added in the Stations site entry for that station. Aerial photos from the Retrolens site going back to the 1930s and 1940s are being referenced to help determine the history of the route and stations, as well as additional documentation from a number of sources including Archives New Zealand. In a number of places deviations and curve easements have been effected. In the Picton Section these include:

• At the Ure (Waima) river bridge the combined bridge was replaced in the mid 1970s, this resulted in a small deviation of the railway on the new bridge alignment and the elimination of an overbridge just north of the river due to highway realignment.
• The Tar Barrel Tunnel (No.21) was bypassed with a deviation in May 2021. The tunnel is being filled in and sealed. A new underpass was constructed to take the highway over the top of the railway.
• A sharp curve was realigned between 267 and 268 km in the mid 1970s. Highway realignment also resulted in a bridge being removed and level crossings eliminated. There was also a proposal for a small deviation between Mirza (165 miles) and the above location in the mid 1960s. This appears not to have been built but earthworks were carried out in the area in the mid 1970s probably for weatherproofing or formation stabilisation.
• A sharp curve was realigned near Taimate Station (date unknown). A deviation was proposed between Lake Grassmere and Blind River stations in the mid 1960s. This appears not to have proceeded but earthworks were undertaken in the area in the mid 1970s probably for weatherproofing or formation stabilisation.
• The Hog Swamp Bridge south of Seddon was replaced in the early 1940s on a realignment of the existing formation, alongside which the old bridge piers remain visible.
• The Awatere River dual level combined bridge north of Seddon was altered in 2007 when the lower road deck was removed, having been bypassed by a realigned highway on a new bridge to the west. The rail deck remains in operation. There has been a recent proposal to create a cycleway on the lower level.
• In the Dashwood Pass, one of the oldest sections of the MNL, several curves have been realigned. Two original tunnels were daylighted in 1979 and 1981, and highway overbridges have been replaced on new alignments.
• The main line through Blenheim was realigned in 2000 when the station was relocated a few metres eastward to make way for a new highway alongside.
• The railway has been realigned multiple times at the Wairau River north of Blenheim with bridge replacements (the current bridge is the third or fourth at this location).
• North of Tuamarina a new tunnel (probably cut and cover) was constructed sometime in the 1950s to eliminate a level crossing with the highway. This entailed a small realignment of the railway.
• Several sharp curves were realigned in the Para Valley between Tuamarina and Elevation. Most of this took place before 1947.
• There was a minor realignment at Para station probably in the late 1960s when a small bridge was filled in.
• A highway overbridge at Elevation was replaced on a new alignment in the 2000s.

So the above are examples of additional detail that has been obtained from aerial photos, some of the other detail for the Wharanui to Picton section will include maps of Wharanui, Mirza, Ward, Lake Grassmere, Seddon, Dashwood, Vernon, Riverlands, Blenheim, Spring Creek, Tuamarina, Koromiko, Elevation and Picton. The latter has changed a great deal due to the large volume of rail ferry traffic.

The story of the Main North Line and Volume 10 will be repeated in all of the other 11 volumes and that is the change that has been achieved in the scope and development of this project due to the availability of aerial photography both historic and current. As an illustration of this, the existing Main North Line volume series of static maps which numbered 168 when produced three years ago, are currently being extended in the Wharanui to Picton section and there are now 288 maps with more being added daily. Most of the new maps are aerials and often there are multiple generations at the more significant sites. The production of these historical maps depends on the free georeferenced map downloads from the Linz Data Service website which in turn enables the historical aerial photos to be georeferenced themselves. This is the most time consuming aspect of the project but has enabled a great deal more historical detail of the railway network to be documented and is considered to be of great value and set the project apart from other maps and historical resources which have been produced previously.

The Volumes and Stations sites are currently being developed and content has been created in both in the last few months. The Volumes site is being updated with a new PHP based section for displaying the maps in each volume that will not be dependent on WordPress, making it a lot simpler to maintain with just a few hundred lines of relatively simple free open source code without lots of bells, whistle, complexity and expense that would be incurred in third party WordPress plugins. It is hoped to integrate this into WordPress as far as is feasible for a seamless user experience at the site, making use of the capabilities WordPress provides to index site content and make it easy for users to locate the content they require. As each volume is created in the Volumes site, entries will be created for each of the stations in the Stations site and linked back into the Volumes site. The development of these two sites to complement the Webmaps site is where most effort is going at the moment in the project and where we expect to see major progress in the second half of this year.