Friday, 11 May 2018

MSL Lyttelton-Rolleston [2]: Christchurch Station 2

Working with Gimp over the past couple of days has led me to knowledge that will massively speed up the creation of mosaics. Briefly that is the ability to drag-rotate an image in place with a preview of what it will look like for each rotation, and to drag-scale an image in place with a preview, likewise. You then click the appropriate button and the image is actually rotated or scaled. As up until this point especially the scaling step has been very time consuming trial and error guessing the size needed because the scaling step itself is slow, it can take 5-10 minutes to complete a scale and then if it is wrong you have to undo and try again with new numbers. So because of this I expect this phase to speed up greatly. 

At the moment I am just finishing the West section of the map up to and including B Shed. The Centre section will follow fairly quickly after that. Having fewer scaling and rotation steps, apart from increasing the speed of mosaic production, will also reduce the quality loss from multiple processing steps. Some of the early mosaics I did of Central Otago had lost quite a lot of the archival image quality by the time they got into the maps. Some of this, however, was also down to choosing the best interpolation algorithm for processing.

B Shed and part of the main station yard as seen in Gimp. The West mosaic is just about complete and part of this project will become the Central mosaic as it makes use of the same aerial image, 2345-B-12.