This dataset provides building outlines within mainland New Zealand extracted from multiple years of aerial imagery, allowing you to see change over time, or restrict the dataset to building outlines that match a specific aerial imagery source.
A building outline is a 2D representation of the roof outline of a building which has been classified from LINZ aerial imagery using a combination of automated and manual processes to extract and refine a building roof outline.
Building roof outlines observed in aerial imagery larger than or equal to 10 square meters are captured in this dataset, and may include structures such as garages and large sheds.
This dataset contains all building outlines which have been extracted from multiple years of aerial imagery available in each region of the country, including the most recent imagery. This dataset includes the dates for which each building existed in the aerial imagery.
Coverage areas include Northland, Auckland, Waikato, Bay of Plenty, Gisborne, Hawke’s Bay, Taranaki, Manawatu-Whanganui, Wellington, Tasman, Nelson, West Coast, Marlborough, Canterbury, Southland and Otago. This dataset will be updated and expanded as new aerial imagery becomes available.
Please refer to the [NZ Building Outlines Data Dictionary](https://nz-buildings.readthedocs.io/en/latest/introduction.html) for detailed metadata and information about this dataset.
**Related building outlines data**
[NZ Building Outlines Lifecycle](https://data.linz.govt.nz/table/101291) – stores the relationship between building outlines when one building is split into two or more building outlines, or when multiple building outlines are merged into a single outline. Use this in conjunction with the NZ Building Outlines (All Sources) dataset.
[NZ Building Outlines](https://data.linz.govt.nz/layer/101290) - provides current building outlines only, derived from the latest LINZ aerial imagery.
**Source imagery** Resolution of the aerial imagery used for building outline capture ranges from 7.5cm pixel resolution (0.075m GSD) to 50cm pixel resolution (0.5m GSD). The source imagery is linked via the capture_source_id attribute of building outlines to the imagery_survey_id of NZ Imagery Surveys. Using this link, additional attributes can be connected to building outlines - for example the dates that the imagery was captured and the accuracy / ground sample distance of the imagery used.
The NZ Imagery Surveys data dictionary is here: https://nz-imagery-surveys.readthedocs.io/en/latest/index.html
**Accuracy Specification:** The Building Outlines contain spatial detail reflective of the visible characteristics of building outlines as seen from the source aerial imagery. The building outlines were created by both an automated and manual method of feature extraction. Outlines are captured in full where they are partially occluded by vegetation or require additional viewer interpretation, and squared off at 90 degrees if the corner angles are between 80-100 degrees.
**The following criteria were used for capturing buildings as building outlines:** • Buildings under construction, caravans, caravan trailers, house boats, shipping containers and other mobile structures are not captured as building outlines. • Primary building structures are captured as separate building outline polygons when the roofs are separate from nearby building roof structures. • Building extensions, sunrooms, balconies, patios and annexes are captured as part of the primary building outline structure if they exist as part of multi-level buildings and if sufficient imagery resolution allows this determination. • Permanent building structures such as sheds and greenhouses >10sq meters, not attached to a primary building structure, are captured as a separate building outlines. • Adjoining townhouses are not captured as separate structures, but rather as joined primary structures. • Adjoining commercial buildings are captured as separate building outlines when rooflines allow delineation. • Hay bales and silage are not captured as building outlines. • Building outline polygons captured will be greater than 10 square meters. An exception to this is in national parks, conservation areas, and wildlife areas where small structures such as huts, bivies and shelters are included as building outlines to address safety concerns in remote locations • Water tanks are captured as building outlines when their area is at least 16.5 square metres (or 4.5 meters in diameter).
**Valid Geometry:** A building outline polygon is considered to have valid geometry if; • It does not overlap with other building outline polygons; • It does not contain any spikes along edges; * It does not contain duplicate nodes; • It does not contain lines that are intersected with each other; • It can contain polygons with interior rings (holes); • It does not contain polygons with multiple exterior rings;