Sunday 1 April 2018

Otago Central Railway [61D]: Finishing Maps - Cromwell-Alexandra 2 / Polygonal Styles 2

Below are two samples of Cromwell and Clyde which show the type of styles I am adopting for buildings, structures and sites.


These samples show how the new styles are applied to fills such as sites, buildings and structures. This has come about because whilst I already worked out how to apply a white border to markers and path styles, making them more visible on dark or diverse backgrounds such as aerial photos, it is only just in the last couple of days that I worked out how to do this with fills.

The idea of changing from solid fills (black, grey or white) to transparent fills with a solid border, is to enable whatever is underneath that fill to be visible, which often is what we want with aerial photography whether historic or current. The solid fills blocked out too much of the detail and that was one deterrent to making more widespread use of aerial photography as a map background. In the styles you can see above, I still need to do some experimentation with different line thicknesses and dash/dot patterns to see what works best.

This means that a "rail map" by default will have the aerial photography background whether current or historic, so that is the definition to be used. A "rail diagram" will be the same map data but with a plain or faint background, usually a terrain relief layer. This high contrast option will enable more topographical data such as contours, heights, waterways, property boundaries and so on that doesn't display well against aerial photography, to be viewed, because I am not changing the styles of every piece of this data to make it visible against all backgrounds - because I want to reduce the clutter on "rail map" tiles.

As I have all but finished Addington I will be again focusing on the Central line to complete the maps which still have a lot of work needed. So far I have got from Cromwell to Clyde. The more complex stations like Clyde and Alexandra which both need a lot of tidying up will take a bit of work. Most of the other detail back to and including Ranfurly is completed. From Ranfurly down to Wingatui still needs a lot of detail and will probably take a month or three depending on what else I am working on at the same time, as I also want to push ahead more or less simultaneously with MNL, or alternating bits of both.

After playing with the styles a bit more this is the best compromise I can come up with.

Obviously we want the lines to be as undominating as possible but if they are too thin then it is too hard to tell the difference between a black line and a grey line so the thickness of the lines is the minimum as shown here and this map is another which illustrates the key reason why changing these styles has been desirable in the first place. This has been a very difficult issue to resolve over many months so I am quite pleased to have got a workable solution that now allows me to get the best possible result with the use of aerial photography backgrounds on maps. The single lines (solid or dashed) are used for buildings and structures, while double lines (solid or dashed) are used for sites.

What you can see in the image of the modern Clyde yard further up this post is noticeable misalignment in the 1977 aerial photography. The mosaics for the second Clyde station area were produced as separate Gimp projects for each generation, which is not now I would do things today as I would have put all the images into one project and just turn different layers on and off to get the required results for each rendering. This means the next stage is to do another Gimp project this time using all the aerial stuff in one project and rendering the different generations out of that one project. So work has to start on that right away as the Otago Central Railway maps have to be finished ASAP.