We’ve added several new attributes to each building outline.

These attributes provide context and make it easier to work with a dataset of this size — for example they enable filtering to a specific administrative boundary or identifying building outlines that have recently been modified.

Capture attribution

The method and source from which building outlines have been captured provides important context — particularly the relevant dates for the source.

capture_method : Generally Feature Extraction or Trace Orthophotography. Feature extraction consists of image processing techniques to determine building outline geometries from imagery. Trace orthophotography is where a building outline has been manually digitised from imagery.

capture_source_group : For all building outlines in the current dataset, the relevant capture source group is NZ Aerial Imagery.

capture_source_name : The name of the capture source is the name of an aerial imagery layer also freely available on the LINZ Data Service, for example Auckland 0.075m Urban Aerial Photos (2017).

capture_source_from / capture_source_to : This is the date range for the capture of the related aerial imagery. We can therefore be confident that the physical building existed at some point within this range.

Deduplication of geometries

The pilot layer contained building outlines from overlapping capture sources — so in some areas the same building was captured twice or even three times.

NZ Building Outlines only contains one representation of a building, making this layer immediately suitable for visualisations of New Zealand’s buildings.

NZ Building Outlines (All Sources) contains multiple representations of a building — one for each of the capture sources that LINZ has obtained. This allows building outlines to be filtered to those that match a specific imagery source.

It also allows comparative analysis over time.

Below are the same building outlines, symbolising new, matched and removed buildings between the 2015 and 2017 captures. You can view them against the two different imagery sources by changing the layers in the top right of the map window.