Topographic differencing shows changes to the Earth’s landscape, vegetation, and the built environment from both natural and anthropogenic processes. Here, we present several examples of topographic differencing in New Zealand that show airplane movement at the Auckland Airport, sediment erosion and deposition along a river on the South Island, and building construction in Wellington. The lidar topography datasets used in these examples are managed by Land Information New Zealand (LINZ) and are available from OpenTopography.
As organizations continue to invest in collecting high resolution topography datasets, more areas are covered by multi-temporal lidar data. This creates an important opportunity to measure how urban and natural landscapes change over time by comparing two or more topography datasets. However, the tools for conducting differencing analyses require a high degree of geospatial expertise and are computationally intensive. OpenTopography's on-demand topographic differencing tools have overcome many of these challenges and offer our community the opportunity to perform streamlined differencing via OpenTopography's user-friendly interface with compute resources at the San Diego Supercomputer Center. These examples were all made with OpenTopography's on-demand differencing tool. Learn more here.
Taxiing airplanes at the Auckland Airport
Move the slider to see the location of the airplanes parked at the terminal and taxiing along the jetway at the Auckland Airport during the 2013 and the 2016 lidar acquisitions.
This example shows airplane movement at the Auckland Airport. Do the red planes indicate airplane position during the 2013 or the 2016 acquisition? What about the blue planes? Test your answer with the slider in the image above. (Answer: Red represents airplanes during the first acquisition in 2013, and blue represents airplanes during the 2016 acquisition.)
River Erosion and Deposition in Blenheim, South Island
This example shows river erosion and deposition along the Wairau River in Blenheim located on the South Island of New Zealand. Specifically, this example shows digital terrain model (DTM) differencing. A DTM represents the height of the Earth’s bare surface with vegetation and man-made objects ideally removed.
Digital terrain model differencing along the Wairau River. Along the river, red represents erosion and blue represents deposition, as well as an increase in the water level. In the southeast of the image, the red and blue shapes represent landscape changes from agricultural activity.
Construction in Wellington, North Island
This example shows the construction of housing and other buildings near the beach in Wellington and is made by differencing digital surface models (DSM). DSMs represent the elevation of the top of the landscape from the natural and built environment. DSM differencing over the built environment, like this example, supports work in infrastructure asset management aimed at efficiently locating new developments as well as changes to buildings.
Optical imagery available from Google Earth shows new buildings constructed between 2012 and 2019.
Do you work in academia, government, or industry and are interesting in working with OpenTopography on topographic differencing? Get in touch with our team at email@example.com.