Tuesday, 5 February 2019

Main North Line [0B]: Volume 10 Progress Report [1]

As part of the development work on various volumes, I am currently working to get a full set of maps of the Main North Line and mapping a few stations in North Canterbury. You can expect to see some maps soon of Amberley, Glasnevin, Waipara, Culverden and possibly some stations on the Waiau Branch, and places further north and south of Waipara, as opportunity permits.

So I have to get a full set of contemporary aerial photography. The tricky area is from Addington to Waipara, where I have to join together images from four different source layers. Firstly there is the 0.075 metre coverage of Christchurch City all the way up to the Waimakariri River. Then after that there is 0.3 metre rural coverage of North Canterbury, but also with Waimakariri District urban coverage of Kaiapoi and Rangiora at 0.075 metres, and Hurunui District urban coverage of Amberley and Waipara at 0.125 metres. And of course to add complexity the powers that be have created aerial tiles that have thick black borders in inconvenient places around the edges, which means I have to make up bridge tiles by bringing in the lower res surrounding stuff and scaling it to a larger size and then masking out the black bits. Since these areas are generally around railway stations, the mosaic for removing the black edges will be combined with historical overlays. Because I have discovered the 0.125 metre coverage of Waipara, I am redoing the mosaic that I already had for this station to take advantage of the better resolution which will improve the official NZR survey historical aerials, just like I have done in other areas. 

0.125 metre coverage of Waipara in a GIMP project with 0.3 metre imagery added top and bottom to remove the most critical black edges. The 0.125 metre tiles will be exported and used as base imagery in place of the ones from Linz.

I have created a mosaic for Amberley with the 0.125 metre imagery and overlaying historical aerial images from 1961, 1976 and 1986. It now needs to have the 0.3 metre contemporary imagery put around the edges of the 0.125 metre images to achieve the same outcome as shown above for Waipara.

Amberley seen in 1961 with the earlier (and larger) station and goods shed. By the time I came to know Amberley in the mid-1980s both buildings had been replaced with much smaller ones.

Glasnevin is another station of interest between Amberley and Waipara as it was still open in 1961 when aerial photos from the same series used for the above are available (as was Greneys Road just south of Glasnevin). There was a lime loading siding and ballast pit there which were still in use at that time. The remains of both are extant today.

The Waiau Branch has been looked at lately as well and Culverden in particular has good quality coverage and maps have been drawn and are just waiting to be blogged. Of course I posted stuff for Rotherham fairly recently. We will have to see what we can achieve with some of the other stations that have limited coverage. Hundalee is another North Canterbury station I have mapped recently.

Once north of Waipara the same 0.3 metre rural aerial photos are needed to get us as far as Parnassus. From there all the way up to Ward we have continuous good quality aerial imagery from the recent quakes but with obvious issues with track movement in places so I am not sure if it will be totally useful or whether I need to use the existing coverage as a backup. Then from there, is Marlborough rural aerial stuff, and I hope there will also be coverage at higher resolutions for places like Picton, Blenheim and Kaikoura.