Wellington City Council

New bird's eye view delivers clear picture of capital

Terralink International's GIS Project Manager John Kotrotsos says their latest project for Wellington City Council has set the standard for aerial photography and mapping. He believes that both council staff and the general public are set to reap the benefits.

A new level of accuracy

The year-long project involved taking aerial photographs using a high-resolution digital camera that captured the capital's landscape down to 0.1m resolution, and processing the photographs to produce incredibly clear imagery.

"The aerial photography covering the entire project area was captured in a single day. This helped our orthophotography processing because it minimised any tonal, shadow and colour variations in the raw imagery. The final orthophotography looks stunning and the clarity is phenomenal," says Mr Kotrotsos.

He says the last time a fly-over of Wellington was completed was in 2006, and since then new technology has meant that the level of detail which can now be captured has improved significantly.

Wellington's CBD required high forward and lateral overlapping aerial photography, planned specifically to minimise building displacement, and to allow for "true ortho" processing techniques.

"It has given us a true bird's eye view, limiting building displacement to less than three metres for even the tallest buildings. This means objects that were previously obscured by building lean are now visible, revealing greater detail."

Mr Kotrotsos says that Terralink used the very latest GIS techniques and software to complete the project, which also included the updating of the council's building and transport network datasets.

"The council specified that they wanted the level of accuracy to be + or - 0.3 metres, so what you see on the screen would be as close to the physical reality as possible," he says.

Something for everyone

Mr Kotrotsos says the ortho-rectified imagery is the "must-have" background layer of any GIS system.

"Now that the council has the latest accurate starting point, different groups within the council can add their own specific vector data over the new imagery to suit their own purposes," he says.

"There are so many uses for this information, not just for council staff but also for the general public. With new applications, it's now possible for the information to go wherever you go.

"For example, council staff can check council gardens and parks to assess the weed and pest situation, and while they are in the field refer to the database to check boundaries and potential hazards.

"It's also essential for checking property boundaries and the legality of buildings. It's easy to check the aerial view of a property against building consent records to see if a new dwelling has the required consent from the council," Mr Kotrotsos says.

He says the contour lines, which accurately show the height and slope of the ground, bring the images to life, and for areas such as emergency management and town planning, this information is critical.

"In an earthquake-prone region like Wellington, where the threat of a tsunami is very real, knowing how high the land is as you move away from coastal areas is very important. Emergency management can determine how far a wave of a particular size and volume may travel, and which areas of the city and population would be at most danger, because they can reference the contours of the land. They can also see what buildings, roads and amenities are most at risk when the big one strikes."

Mr Kotrotsos says that the new imagery is also being used to help Terralink to update its core NZ MasterMap datasets, as well as being available to all organisations either as single tiles, or as a complete dataset, through a range of Terralink's products and services, including their new image server technology.

Getting the job done right

Mr Kotrotsos says the main advantage of the new data set for Wellington City Council is they can now be confident they are making decisions based on the latest, most accurate imagery and data sets.

"We took great pride in completing this comprehensive project for the council and in exceeding their expectations. It was well managed by both parties and produced to the highest of standards by our very experienced photogrammetric team."

Wellington City Council team leader of enterprise data management, Michael Brownie, says;

"We have been very pleased with the way Terralink managed the project and the quality of the information is excellent."

In an environment where there is an increasing need and demand for high quality and accurate imagery and data, "how, when and where you need it", this project is helping to set the benchmark.

"The accuracy and detail we produced was exceptional, and Wellington City Council staff can now see every kerb, footpath and property boundary at the push of a button, without leaving the office," Mr Kotrotsos says.