Friday, 6 July 2018

Wairarapa Line [2]: Gracefield Branch 2

Well the last couple of days have been work in downloading the aerial photography needed to do the Gracefield Branch. This is split up into three sections: Woburn station, Hutt Park station and Gracefield station.

At the moment I have completed a mosaic for Hutt Park and am working on the mosaics for Woburn and Gracefield. Normally when creating a mosaic you have to overlap to the adjacent mosaics on all sides in order to ensure the tiles all line up properly when you bring them into the GIS. So I have to create a part of Woburn using the aerial imagery that is then used to overlap onto the Hutt Park aerial imagery, which in its turn overlaps onto the Gracefield aerial imagery. Hence the Gimp project has started with a large grid of 28 LDS tiles (4x7) covering the entire section from Woburn to Gracefield, which has now been split into three pieces. The Woburn piece will be further expanded with extra tiles and imagery because it only covers a part of the station, just the part that was in the first aerial image, which has been cropped to the edge of the tile boundary between Woburn and Hutt Park. The Hutt Park piece will be used to align the Gracefield imagery before it gets cut up into Hutt Park and Gracefield tile sections.

The mosaic for Hutt Park has now been extended with 1978 coverage which was such a high resolution that two images are needed to cover the area. The full set of images for 1939, 1978 and 2017 are below.