Good morning. Last week’s blog referred to samples of Southdown and suggested a method of providing access to specific levels of aerial photography for each station. This week, instead of other map work, time was taken to reflect on further options for displaying aerial photography, and even although another week has gone by with seemingly limited progress, having arrived at what we believe to be a much better solution for displaying aerial content, we don’t regret having waited, for the implementation of this solution will be far simpler to create as it does not require a specific solution for each individual station and is practically seamless for the end user.

Leaflet (the Javascript library that runs in the web browser to provide the user interface) has within it the capability to switch the display to different layers. This includes allowing the selection of different base layers, as well as allowing overlays to be displayed on top of a base layer. By leveraging this capability, we have created sample Diagrams for Westfield-Auckland at zoom levels 12-19, and sample Aerials for the same area and zoom levels from 1972 only. (Although previous demos have gone up to zoom level 20 in aerial photos, we’ve settled on level 19 for now, because of the volume of output that will be produced, so there is enough room on the server to store all of it. Also, we will still have to have some non map galleries for stations that we don’t have aerial maps for, like we were doing for some stations on the Smugmug site.)

The demo web page for demonstrating this multi layer capability is here:

https://blog.nzrailwebmaps.nz/maps/Volume-1-North-Auckland-Line/

When you go to that site you’ll see this:

This is similar to what our other demo pages have shown, with the zoom buttons top left, but now you have a layers button top right (the thing that looks like a stack of paper). Click on that and a little menu pops up, giving you the ability to choose between Aerials and Diagrams (diagrams is the default). The effect is easier to see when you are zoomed in a bit (maybe to level 17 or so). So now you can go between one and the other seamlessly for a particular location and compare them easily.

In a lot of areas, of course, there is more than one generation of aerial photography available. So the next demo, which will be Volume 6 Wairarapa Line, one of the existing completed volumes, will include multiple levels of aerial photography, and therefore have these multiple layers able to be switched between. We’ll put a post up when that is ready for testing, as it will take a while to format a different project with the webmaps specific styles in the GIS, and export all the tiles needed, especially for multiple aerial eras. For now, enjoy what you can see in the latest Volume 1 demo.