Add an option so north is shown directly upwards
For some reason the map is rotated -2 degrees from vertical
You'll notice this "rotation" is different depending on how far north / south you're looking in New Zealand. The reason for this is that LINZ produce the topos using the NZTM coordinate system, but at present I'm overlaying these on to Google Maps which uses the WGS84 coordinate system. To wrap the topos onto the Google Map the images need to be warped a little between the two coordinate systems.
The reason I use Google Maps is that it allows me to add the opacity functionality where you can ghost out the topos to varying degrees and look at the satellite imagery for the same location. Some users find this useful.
In the future I may look at using a different map option to display the topos on, so the grid doesn't get warped, but if I can't find a satellite imagery layer already projected into the NZTM coordinate system then it will mean sacrificing the opacity functionality a lot of people use.