patrickdunford.nz

Category: NZTekonverse -> Qgis

NZRM Webmaps Development Update 2021-03-17 [1]

One of the features of this blog is that it includes technical posts about the NZ Rail Maps project with which converser.nz blogs are affiliated. These posts are less suitable for a general audience mainly interested in the map content and so are posted on NZTechonverse instead. The NZ Rail Maps live webmaps project is…

2021-03-17
NZ Rail Maps: Spatialite vs Geopackage

In the NZ Rail Maps project, I have preferred in recent years to replace shapefiles with databased formats. When using file based dbms (vs client-server) SQlite stands out as a viable alternative that is extremely well supported with an impeccable reputation. There are a number of SQlite based formats of data for GIS layers. Geopackage…

2021-02-06
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