This AI Pack can be purchased as an add-on to the Residential Building Footprints pack. It adds AI Layers and AI Parcel outputs related to:

  • The dominant material of the roof (shingle, tile, metal or other)
  • The presence of various structural shapes on the roof (hip, gable, flat and turret presence)
  • Trees overhanging the building.

Roof Material

Roof Material includes a group of three AI Layers:

  • Tile
  • Shingle
  • Metal

It also includes a "dominant roof material" category in AI Parcel exports (both as a column in the spreadsheet and as an attribute associated with a building footprint polygon in the GeoPackage file), which can take the value of "Tile", "Metal", "Shingle" or "Other".

The Dominant roof material is the material taking up the largest horizontal area of the roof. So a roof containing both tile and metal will be denoted by the material covering the largest fraction of the roof (unless the majority of the roof is neither tile, shingle, nor metal).

If there is no clear dominant roof material, it is classified as "Other".

Definition

Tile Roof

Roof tiles are defined by their structure and thickness: clearly laid out lines with shadows on each row, and ridge caps. As such, this includes any tile materials (primarily terracotta or concrete), regardless of colour.

Terracotta tilesConcrete tiles

Metal Roof

Roof comprised of metal sheets, typically zinc, copper and steel alloys, regardless of whether they are smooth, corrugated, or with distinct ridges. As can be seen in the statistical performance figures, metal is the most challenging roof type to detect correctly. Some metal is clear (with corrugated ridges). However, particularly in the US, metal roofs are often flat and relatively uniform in colour, and can easily be confused with other types of roof that are similarly featureless or contain ridges that may look like corrugations.

Corrugated metal roofs

Copper roofs

Shingle Roof

Roof comprised of a patchwork of shingles. Roof shingles are a roof covering consisting of individual overlapping elements. These elements are typically flat, rectangular shapes laid in courses from the bottom edge of the roof up, with each successive course overlapping the joints below. Visually, they have less distinctive straight ridge lines and clear rows compared to tile roofs. We do not distinguish between wood, metal, laminated asphalt, or any of the numerous shingle materials nor colours.

Asphalt shingles

Wood shingle/shakes



Other Roof

Any roof material not described by the materials defined above. As we add more roof materials in future releases, "Other Roof" will reduce in scope to exclude them.

Concrete roofsAsphalt/Fibreglass roofsVery poor condition roofs with difficult-to-determine material


Characteristics and Recommended Use

The dominant roof material is provided to avoid confusion in the very common situation where a shingle or tile roof has a small metal extension. In some situations (due to lighting conditions for example) it can be very difficult to tell the difference between tile and shingle, or between metal and other fairly featureless roof types. This shows up as less bright areas in the AI Layer viewer. The dominant roof material simplifies this information by making the best choice of overall roof material given the information available.

Tiles are much less common in certain parts of the US, which means that the majority of roofs identified as tile are lower confidence. This is because a certain percentage of shingle roofs will always be mistaken for tile, and an absence of actual tile roofs means that these errors form a much larger percentage of those detected as tile.

Shingles are almost never used in Australia whereas they are the most common roof type in most parts of the US. This means that the majority of roofs in Australia identified as shingle are lower confidence. This is because a certain percentage of tile roofs will always be mistaken for shingle, and an absence of actual shingle roofs means that these errors form a much larger percentage of those detected as shingle.

The practical performance of the metal roof attribute varies with region, depending on how prevalent it is, and how common other roof materials are.

The lower number of "Other" roof material in Australia means that less of the "Other" predictions are confident (as Australia is almost exclusively tile, metal and concrete roofs).

Confidence Distribution by Region

Please refer to Confidence for a further explanation of this value and best practices in using this score to filter the data according to your use case.

Tile Roof

Australian Data

US Data
WestMidwest


NortheastSouth

Shingle Roof

Australian Data


US Data
WestMidwest


NortheastSouth

Metal Roof

Australian Data

US Data
WestMidwest


NortheastSouth

Other Roof

Australian Data


US Data
WestMidwest


NortheastSouth



Roof Shape

Definition

The set of roof shape attributes each detect whether there is at least one structural element of the roof with that definition.

Hip

All parts of the above roof are hip

A roof, or part of a roof, that is made up of three sloping triangles (more than three are considered a partial turret).

At least one hip element on the roof (either a whole hip end, or a small "mini hip" joint as part of a more complex roof).

Gable

At least one gable element on the roof (similarly, a large end of a building, or a small gabled roof feature). A roof, or part of a roof, that has inverted "v" shaped ends.

Flat

At least one flat panel on the roof (including a small covered balcony extension, as long as the roof is permanent, not fabric awning).

Turret

The centre house has a partial turret

At least one round, pointed turret (made of connected triangles pointing to a common centre). The definition includes both full round ones, and a half turret feature that is comprised only of a few triangles that do not form a complete circle.

Roof drawings courtesy: https://unitecontractors.com/roofing-contractors-boston-services/

Characteristics and Recommended Use

The Roof Shape data differs from that of Dominant Roof Material, in that there is no sense of an overarching dominant shape. For example it is difficult to determine the dominant shape be of a rectangular building with one hip end, one gable end, and a turret on the side. By the same token, no reasonable area estimate can be provided. Viewing the AI Layers you will be able to identify a blob around the key part of the feature, e.g. the corner where three panels join for a hip. This blob is carried over and attached to the relevant building when an AI Parcel is exported.

The main reason flat roofs have a low confidence is that a "shed" roof (flat section at a slight angle greater than a few degrees) is marked as incorrect. The other reason is fabric awnings protruding over a balcony are almost impossible to distinguish from a top down aerial image, and the model is more cautious at predicting the presence of flat roofs. If you don't required this distinction, you can safely include lower confidence flat roofs.

The primary reason for turret roofs having low confidence is that they are rare, small features. In practical use, high confidence turrets tend to be the clearest, sharpest examples of full round turrets. The lower confidence turrets are the partial ones that can look like a cross between a turret and fancy hip (with e.g. 4x triangles meeting to cover a building end or corner, rather than three).

Confidence Distribution by Region

Please refer to Confidence for a further explanation of this value and best practices in using this score to filter the data according to your use case.

Hip

Australian Data

US Data
WestMidwest


NortheastSouth

Gable

Australian Data

US Data
WestMidwest


NortheastSouth

Flat

Australian Data

US Data
WestMidwest


NortheastSouth

Turret

Australian Data

US Data
WestMidwest


NortheastSouth



Tree Overhang

A "Tree Overhang" AI Layer is available for viewing. Polygons of tree overhang, as well as area estimates are available in an AI Parcel export.

Definition

Any case where there is some tree (leaf on or off) protruding over the top of a Building Footprint.

Characteristics and Recommended Use

When presented as a "Y" or "N" flag, Tree Overhang may not be directly useful. It detects any amount of overlap at all, such that more than half of the properties in our coverage area are listed as having tree overhang. Where the overhang is used to identify trees that may need trimming, or calculating property risk, it is recommended you use the area estimate to set a meaningful threshold (e.g. only look at buildings with >10m2 of overhang). In more advanced use cases, you would use the area directly to rank properties from highest to lowest amount of overhang, or as a continuous variable to use in a statistical model. In more advanced usage you would consider the shape and position of the tree overhang sections on the building, obtained from the geospatial file of exported AI Parcels.

Note that the tree overhang is calculated on Building Footprints before enhancement algorithms are applied. This means that the tree overhang polygons do not always push quite to the edge of e.g. the sharp corners introduced by the enhanced Building Footprint polygons.

The confidence values for Tree Overhang are particularly low, because the edges of trees that overhang a roof often fade out gradually between high confidence and very low confidence. The area estimate of Tree Overhang is recommended as a better means of adjusting whether mild, moderate or extreme overhang should be included for your particular application.

Confidence Distribution by Region

Please refer to Confidence for a further explanation of this value and best practices in using this score to filter the data according to your use case.


Australian Data


US Data
WestMidwest


NortheastSouth