Category: NZ Tekonverse -> NZ Rail Maps Technical

DreamHost vs GoDaddy vs local… webhost pros and cons

Well this time around I am going to write about the choice of webhost platform. Web hosting these days can be a lot cheaper than it might have been in the past as there is a lot of competition. In New Zealand you can get quite reasonable web hosting with 150 GB of disk space…

2020-12-11
NZ Rail Maps: Using Gimp To Georeference Retrolens Aerial Photos [7]: Extracting Mosaic Tiles

So I have been trialling the alternative overlay method with more files and have decided to redo all the mosaics for Auckland so far. This is a few days’ work but as there are already some issues with accuracy in some of the more hilly areas or where the embankment is raised, it is going…

2020-06-02
NZ Rail Maps: Using Gimp To Georeference Retrolens Aerial Photos [6]: Alternate Overlaying Technique

Today I am going to look at an alternative way of stitching together the source layers. I have to do a set of mosaics for the station of Kamo, which is the northernmost part of Whangarei. From a rail perspective there were two stations there. Just a little south of Kamo there was a coal…

2020-05-25
NZ Rail Maps: Using Gimp To Georeference Retrolens Aerial Photos [5]: Overlaying Multiple Layers

So in my last post I showed how to get started in georeferencing with the first overlay. In that post I put the second layer in to show how it would join onto the first layer. The aim of this part is to show how to add additional overlays and how to deal with the…

2020-05-24
NZ Rail Maps: Using Gimp To Georeference Retrolens Aerial Photos [4]: Getting Started With Overlaying

So now we can look at how we actually do the georeferencing. This happens as a multi part process, and explaining the steps gives you an understanding of how it all works. The basic of georeferencing a historic aerial photo, is that by aligning it to a current aerial photo, of which we know the…

2020-05-24
NZ Rail Maps: Using Gimp To Georeference Retrolens Aerial Photos [3]: Getting Imagery Into Gimp

So let’s get this rolling. First thing I need is to download the layers from Linz Data Service. Which in this case is at the following URL: https://data.linz.govt.nz/layer/53399-northland-01m-urban-aerial-photos-2014-2015/ The layer is called Northland 0.1m Urban Aerial Photos (2014-2015) and covers the stations of Whangarei, Portland and Kamo. It also covers the port area of Whangarei,…

2020-05-23
NZ Rail Maps: Using Gimp To Georeference Retrolens Aerial Photos [2]: Preliminary Considerations

So I aim to write one post every day about this topic (this post was supposed to be finished last evening but has stretched through until this morning) until all the parts are completed, there are probably three or four parts. This is easy because I am doing georeferencing at the moment on a particular…

2020-05-23
NZ Rail Maps: Using Gimp To Georeference Retrolens Aerial Photos [1]: Introduction

OK so here is another post in the NZ Rail Maps category and this post will explain how I carry out the georeferencing of the historical Retrolens aerial photos to produce the maps for the NZ Rail Maps project. This is a very rewarding aspect of the project but it does take a lot of…

2020-05-21
New “Readjust” feature in Gimp Unified Transform (NZRM Aerial Mosaics)

Unified Transform is a very useful capability in Gimp since about 2.10 that combines a number of transformation tools together, such as Scale, Rotate and Shear. I have used this tool extensively when creating aerial map mosaics for the NZ Rail Maps project. To create an aerial map mosaic, I start with downloading the current…

2020-04-22
NZ Rail Maps Technical Review 2020-04-18

So we are now at Qgis version 3.10.4 for the NZ Rail Maps map production task. Back a way we had a lot of trouble with Qgis with WMTS layers which were unusable at that time. Since then however we haven’t been able to replicate the problem but we suspect that their code has bugs…

2020-04-18