Terralink

Page URL:	http://www.terralink.co.nz/case_studies/wraps_case_study.htm
Date Printed:	Tuesday, 7 September, 2010

WRAPS: Waikato Regional Aerial Photography Consortium project – An update Terralink has recently completed New Zealand’s most ambitious aerial photography project to date, over the entire Waikato Regional Council area. The project was undertaken for a Consortium of local and regional authorities including the Department of Conservation, Waikato University, Environment Waikato and 9 district councils in the region. The project commenced in mid 2001, and the final deliveries were made in early 2003. The nature and size of the project meant a two-year timeframe for supply of the data was always intended. New Zealand’s weather patterns and sun-angle criteria means that every opportunity must be taken to acquire photography. The area covered was some 25,000 sq kms and in broad terms ran from just south of Auckland to south of Lake Taupo and from Rotorua across to the West coast. The purpose of the project was to establish an ortho-image base and a snapshot of the region which would enable the consortium members to look at the region in a new light when it comes to resource management, district planning and effective contract administration. For more sophisticated planning, the imagery and the later-supplied DTM data allow for analysis of flood plains, design of new roads, land use analysis, forestry management, water use and general conservation management. The scale of the job has been significant says Dawn-Lee Hartley, Business Development Manager of Terralink International. Over 3,200 ortho photo tiles were produced. A digital terrain model was first produced which was then used as a surface model to rectify the scanned photography. Photography was “tied” to its true ground position by the use of surveyed detail points acquired via GPS. The ortho photos are at a scale of 1:5,000 with a planar accuracy of +/- 3m horizontally and a ground sample distance, or pixel resolution of 1 metre. This means each pixel on the orthophoto relates to 1 metre on the ground. Careful planning of flight paths and photography lines was carried out to maximise flying time during the aerial photography flying season which goes from August to May. Since the initial deliveries of the data, additional update imagery rectification work and upgrading of DTM data for contour and 3D model generation has been increasing. A total refly of the area is planned, and Terralink are looking forward to providing these services again to the Consortium. The project was a huge success for all parties, and Terralink has now embarked on further similar projects over even larger regions of the country. Terralink plans to acquire a “nationwide” imagery coverage, with the Manawatu-Wanganui, Canterbury, Otago and Southland areas contracted and to be captured over the next two to three years.