To test the rendering algorithms developed in the Blue Mountains prototype, a larger case study with a more varied geomorphology was needed. As I was in Sydney at the time and wanted to be able to explore the landscape of the case study for myself, a short trip down to Tasmania seemed like an obvious choice. The island is rich in significant geological sites and offers a diverse range of surface features, many of which are described in detail in the book “Created From Chaos” by Peter Manchester.
The photographic set “Tasmanian Landscapes” documents a brief trip around the island in late December 2013. It was summer in Australia, but only 12 degrees in Hobart with a slight flurry of snow encountered whilst crossing the Gordon River Dam. The set opens with the flight down the East Coast, capturing a great view of the granite peaks of The Hazards, shown below.
After a trip up the River Derwent from Hobart, the coastline of the Tasman Peninsula was explored, followed by The Hazards and Freycinet National Park, this time from the ground. The terrain then opened up through the Midlands, with views west towards the Central Highlands. The trip then concluded by travelling to Mount Field National Park and along the Gordon River Road into the South West Wilderness.
Elevation data for the study was extracted from the Geoscience Australia terrain portal to cover the whole of the main island of Tasmania, resulting in a dataset of 14426 by 12371 points. No changes were made to the rendering software since the Blue Mountains prototype and, after processing the data, the resulting raster image was 43137 × 36998 pixels.
The following images show some interesting screen-captures from browsing the terrain. The prototype map interface can be found by clicking through on the last screen-capture (please note that there is a tile-stitching error running North/South from Turners Beach to Cox Bight).
Compared to existing web mapping services, the rendered tileset conveys the form of the land with a stylistic, yet accurate and revealing depiction. From a cursory analysis, the balance between continuous mass and structuring line compliment each other well. Notable deficiencies are in the allocation of grey-scale values. The range of higher elevations over the case study is in small areas meaning that darker shading from the hypsometry layer is influencing a large percentage of the land area. Further analysis will follow in a future post, as will the next phase of this project, working with the Ordnance Survey’s UK elevation open data product, Terrain 50.
I have worked extensively with prior Ordnance Survey elevation products, interpolated from manually drawn contour lines. The new dataset is derived from LIDAR scanned data and automatically generalised. I am interested to see how the rendering algorithms work with the new dataset and I include a reference here to existing investigative work carried out by Dr. Christopher Green at the University of Oxford analysing this data.