Project Diary 2019-05-17

We try to post at least once a week depending on what we are doing in this project. Most of the posts are about specific volumes or regions we are working on. Other times there will be a progress report for the whole project like there was last week. This week it will just be a diary entry because whilst we have been doing a lot of map work this week, not a lot of it has related specifically to NZRM.
This week the majority of our time has been taken up with getting a complete set of maps for Christchurch City. This meant downloading a lot of stuff from Land Information New Zealand, because they have a 3.5 GB limit for the estimated size of each download. As it happens, it is more like 5 GB actual download in a lot of cases. But it meant that at a pixel spacing of 0.075 metres, there are a LOT of layers for the whole city. It works out to something like 60 GB. If you have a few dollars you can get them to courier the data layers to you. With the fact we don’t have any spare cash to spend, we just settled for splitting up the city layers into a series of downloads to get all of it. There are some overlaps which means we don’t quite have the expected efficiency and because we inadvertently got some gaps between downloads we had to make some extra downloads to be able to fill in those gaps.
So we now have Christchurch City covered for 2018 (central only), 2015 (whole city), 2011 just after the quake (central only) and c.2010 (actually between 2004-2010 and for some reason the dates aren’t more precise) which again is the whole city. We also have some historical retrolens layers to overlay at some point. We did consider downloading all the 2011 imagery and in fact did set up a series of downloads in Linz but haven’t actually executed those downloads because that imagery is at 0.1 metre pixel spacing and while it is very good it is also just after the quakes so it does have limits. But it is a shame that there isn’t high resolution imagery before then that can be downloaded. Even 0.3 metres would be better than the 0.75 metres 2004-2010 stuff.
As far as the NZRM project actually goes the work this week has been on the Otago Central line. First up is to redo the Cromwell Gorge section with the Retrolens scans of survey 1452 which are distinctly sharper than the original ones we paid for a few years ago, and then particular stations. At the moment Omakau-Cromwell is being considered as one Gimp project covering a number of stations. It is separate from the Cromwell Gorge mosaics because of differing resolutions. The Cromwell Gorge part was originally done at 0.75 metre base imagery because that was all that was available for the whole section, but in 2017 the full area became available at 0.4 metres. But initially all that we did was scale the 0.4 metres to 0.75 metres and overlay it with the 0.75 metre stuff. Now we have scaled the 0.75 metre base to 0.4 metres so as to be able to use this scale base imagery for the Gorge section.