Parent Layer: January 25

Name: 2D Building Footprints Low Detail

Display Field: DATA_SRC

Type: Feature Layer

Geometry Type: esriGeometryPolygon

Description: The 2D building footprint dataset is a 2D representation of building roof extents and should not be confused with the building industry floor footprint. This layer should be used to complement the higher accuracy and detail “2D Building Footprint” dataset (SL_CGIS_2D_BLD_FTPR), which is directly derived from the photogrammetrically acquired 3D Building Models. This dataset is derived from the City of Cape Town’s 2023 high-resolution aerial imagery and nDSM derived from the 2023 LiDAR dataset. The aerial imagery is orthorectified and has three spectral bands: visible red, visible green, and visible blue, with a spatial resolution of 8 cm. The LiDAR point cloud has a density of 10 points per square meter and a vertical accuracy of 0.1m (95%).The dataset is automatically generated using trained Mask R-CNN with Precision, Recall, and F1-score of 0.85, 0.70, and 0.77, respectively; and Unet deep learning models with Precision, Recall, and F1-score of 0.97, 0.89, and 0.93, respectively. The Mask R-CNN model is trained with nDSM, and the Unet model is trained with aerial imagery. These trained models are used to extract building footprints for the entire city. The extracted building footprints showed irregularities, which were then post-processed using ArcGIS's geoprocessing model created with Esri's ModelBuilder. This geoprocessing model is run on the raw extracted footprints to produce a regularized building dataset. Each 2D building footprint has a mean building height calculated from the 2023 LiDAR nDSM.This dataset will be updated periodically to align with the latest acquired LiDAR and/or aerial imagery dataset. The Low-detail footprint layer aims to supply the City with a building footprint layer that has metro-wide coverage.

Service Item Id: 341bb3dd82224b1fabe0ff100039ae08

Copyright Text: Geomatics Branch, Applications | Information Systems and Technology Department, 1st floor Keller House, 121 Loop Street, Cape Town, 8001 Data distributed by City Maps public counter, email: City.Maps@capetown.gov.za.

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Spatial Reference: 102100  (3857)

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Type ID Field: null

Fields:

• OBJECTID ( type: esriFieldTypeOID, alias: OBJECTID )
• DATA_SRC ( type: esriFieldTypeString, alias: Data Source, length: 512 )
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