The NIMT is not an area I was planning to work on in the near future but there has been an enquiry about this section of the former NIMT route, so I am taking a look at the maps I have of it. First thing is to download the LDS aerial photos of the area which are available in 0.1 metre resolution, and then start on mosaics of the route. Retrolens does have some aerial photography at relatively low resolution available from 1941-42. However about three years ago I paid Archives NZ to copy me some contact prints which are at a higher resolution, and date from 1944, so at the moment I am preferring to use these in the mosaics.
When I first started using historical aerial imagery I used to overlay it in Google Earth because that was what I was familiar with at the time. These days of course I use Gimp to produce something I can freely copy and reproduce and trace directly over in Qgis.
The aerial photos used to get overlaid onto GE. This example is at Takapu Road where there is now a major motorway interchange.
This is a Whites Aviation aerial of Takapu Road after the motorway was put through. Some of the railway route can still be seen, prior to the more recent residential development of much of this area.
The above two photos taken 1947 and 1951 both show the site of the old Tawa Flat station.