Open Buildings

A dataset of building footprints to support social good applications.

Building footprints are useful for a range of important applications, from population estimation, urban planning and humanitarian response, to environmental and climate science. This large-scale open dataset contains the outlines of buildings derived from high-resolution satellite imagery in order to support these types of uses. The project being based in Ghana, the current focus is on the continent of Africa.

Dataset description

The dataset contains 516M building detections, across an area of 19.4M km2 (64% of the African continent).

For each building in this dataset we include the polygon describing its footprint on the ground, a confidence score indicating how sure we are that this is a building, and a Plus Code corresponding to the centre of the building. There is no information about the type of building, its street address, or any details other than its geometry.

More explanation is in the FAQ.

Map showing building counts across Africa

Uses of the data

Population mapping

Building footprints are a key ingredient for estimating population density. In areas of rapid change, or where census information is out of date, population estimates are vital for many kinds of planning and statistics.

Humanitarian response

To plan the response to a flood, drought, or other natural disaster, it is useful to be able to assess the number of buildings or households affected. This is also useful for disaster risk reduction, e.g. to estimate the number of buildings in a particular hazard area.

Environmental science

Knowledge of settlement density is useful for understanding human impact on the natural environment. For example, it helps with estimating energy needs and carbon emissions in a certain area, or pressure on protected areas and wildlife due to urbanisation.

Addressing systems

In many areas buildings do not have formal addresses, which can make it difficult for people to access social benefits and economic opportunities. Building footprint data can help with the rollout of digital addressing systems such as Plus Codes.

Vaccination planning

Knowing the density of population and settlements helps to anticipate demand for vaccines and the best locations for facilities. This data is also useful for precision epidemiology, as well as eradication efforts such as mosquito net distribution.

Statistical indicators

Buildings data can be used to help calculate statistical indicators for national planning, such as the numbers of houses in the catchment areas of schools and health centres; mean travel distances to the nearest hospital or forecast of demand for transportation systems.

Explore

Zoom or search to explore, and click on building outlines to see metadata. Alternatively, look at the data in Earth Engine.

confidence >= 0.7
0.65 <= confidence < 0.7
0.6 <= confidence < 0.65

Details

Curious about why some buildings appear offset from the satellite imagery? Or why detection doesn't work as well in areas with dense or complex buildings? See details about data limitations and quality in the FAQs and technical report.

Frequently asked questions

How was this dataset created?

A deep learning model was trained to determine the footprints of buildings from high resolution satellite imagery. Our accompanying technical report describes the methodology.


How is the data licensed?

The data is shared under the Creative Commons Attribution (CC BY-4.0) license and the Open Data Commons Open Database License (ODbL) v1.0 license. As the user, you can pick which of the two licenses you prefer and use the data under the terms of that license.


Why two licenses?

We wanted to make the data compatible for ingestion by those working with ODbL-licensed datasets (namely the OpenStreetMap community) while enabling people who don't use ODbL licensing to use it under the terms of the CC BY-4.0 license. We hoped to take away the burden of figuring out whether the two licenses were compatible and simply release the data set under both licenses.


Can these buildings be added to OpenStreetMap?

Yes – however, to maintain the quality of OSM, please be mindful of the need for human review when adding machine-generated features, and where possible to do this with the benefit of local knowledge. Errors in the data to look out for include false detections and inaccurate shapes (see more about accuracy below). We also recommend starting by filtering out building detections that have a confidence score below the estimated 90% precision threshold.


Are these the same buildings as on Google Maps?

The buildings on Google Maps come from a variety of sources, including the model used to generate this dataset. So there is some overlap, but the sets of footprints are not exactly the same.


Why are buildings offset from satellite imagery in some areas?

As the imagery in Google Maps is updated over time, the specific images used to identify these buildings are not necessarily the same images that are currently published in Google Maps. If there is a misalignment between these two sets of imagery, buildings displayed in the data explorer map may appear to be offset from the underlying imagery.

You can view a timeline of the imagery for a specific area using the Historical Imagery feature in Google Earth Pro which may show this imagery offset between different images and dates. To learn a little more about satellite imagery offset see these sites (1, 2). Also see the technical report for details about data limitations and quality.


Why are the building detections less accurate in certain urban, arid or rural areas?

Despite having a diverse set of training data, some scenarios are challenging for the building detection pipeline, including: 1) geological or vegetation features which can be confused with built structures; 2) settlements with many contiguous buildings not having clear delineations; 3) areas characterised by small buildings, which can appear only a few pixels wide at the given image resolution; and 4) rural or desert areas, where buildings constructed with natural materials tend to visually blend into the surrounding area. See the technical report for more details.


How accurate is the data?

The data is subject to both omission and commission errors, of these types:

Imagery completeness errors: for some areas, up-to-date satellite imagery may not have been available, or there were buildings on the ground that were not visible from the satellite image, or there was cloud cover.

Detection errors: estimated precision and recall curves for our detection model, based on a held-out test set, are as shown below. The tradeoff between false positives and false negatives varies between geographical regions.


Precision-recall curves

Our model sometimes wrongly detects buildings where there are actually rocks or vegetation features, for example.

By choosing the confidence score threshold at which buildings are filtered out, the tradeoff between precision and recall can be controlled. We provide suggested thresholds with each download tile to obtain estimate 80% and 90% precision levels.


Does dataset quality vary per location?

Yes, see plots below. To address this we provide a CSV file with suggested score thresholds to obtain specific precision levels for each download tile.


90% precision confidence score thresholds Fraction of detections dropped at 90% precision confidence score threshold.


How complete and up-to-date is it?

The dataset freshness is determined by the availability of the high-resolution source imagery which we use to detect buildings. While we have tried to include the most recent images possible, particularly in populated areas, in some cases, the most recent image for some location was several years old or not available to us at all. To look at freshness for a particular area, the Historical Imagery function in Google Earth Pro shows the specific dates and imagery (check for imagery before the inference date given in the version history below). Furthermore, we have not processed imagery for the entire continent: to check whether a particular region has been included, the dataset explorer map above visualises all buildings in the dataset.


What is the distribution of confidence scores and building sizes?

We filtered detections to include only those with confidence score 0.6 or greater. Depending on the application, it is likely necessary to filter at a higher threshold (e.g. with the score thresholds above to achieve 90% precision).


Distribution of confidence scores. Distribution of detection sizes.


How can I access the data?

We currently provide 3 options:


How can I download data for a specific country or region?

The data is organised into tiles that can be directly downloaded. Alternatively, the example Colab notebook shows how to download data for a specific region, given the geometry of the area of interest.


Is the imagery also available?

The underlying satellite imagery is not part of this dataset. However, the source imagery used for detections can be viewed in Google Earth Pro. Different time frames can be viewed using the Historical Imagery function.


Will the data be updated or extended?

We hope to continue improving this dataset, by both refreshing it using new source imagery, and by refining the detection model to improve accuracy. Based on community feedback, we may extend the dataset to new areas or add additional features: please let us know, using the contact details below, any queries or requests.


What is the citation for this dataset?

If this dataset is useful, please consider citing our technical report:

W. Sirko, S. Kashubin, M. Ritter, A. Annkah, Y.S.E. Bouchareb, Y. Dauphin, D. Keysers, M. Neumann, M. Cisse, J.A. Quinn. Continental-scale building detection from high resolution satellite imagery. arXiv:2107.12283, 2021.


Who can I contact about issues with the dataset?

Please contact open-buildings-dataset@google.com with any feedback.

Data format

The dataset consists of 2 parts: building polygons and score thresholds.


Building polygons

Building polygons are stored in spatially sharded CSVs with one CSV per S2 cell level 4. Each row in the CSV represents one building polygon and has the following columns:

  • latitude: latitude of the building polygon centroid,
  • longitude: longitude of the building polygon centroid,
  • area_in_meters: area in square meters of the polygon,
  • confidence: confidence score [0.5;1.0] assigned by the model,
  • geometry: the building polygon in the WKT format (POLYGON or MULTIPOLYGON),
  • full_plus_code: the full Plus Code at the building polygon centroid,

Score thresholds

The estimated score thresholds are stored as one CSV. Each row in the CSV represents one S2 cell level 4 bucket and has the following columns:

  • s2_token: S2 cell token of the bucket,
  • geometry: geometry in the WKT format of the S2 cell bucket,
  • confidence_threshold_80%_precision, confidence_threshold_85%_precision, confidence_threshold_90%_precision: estimated confidence score threshold to get specific precision for building polygons in this S2 cell bucket,
  • building_count_80%_precision, building_count_85%_precision, building_count_90%_precision: number of building polygons in this S2 cell bucket with confidence score greater than or equal to the score threshold needed to get the specific precision,
  • building_count: number of building polygons in this S2 cell bucket.

Download

The polygon data (46 GB total) is composed of a set of CSV files, with one file per level 4 S2 cell that range from 0.1 MB to 2.4 GB. Select a download method below.


Download from the map

To manually download data for a specific cell, click on the map below.


Download data for a specific country or region

This Colab notebook shows how data can be downloaded for a specific country or region.


Download all data

Download all polygons using gsutil:
gsutil cp -R gs://open-buildings-data/v1/polygons_s2_level_4_gzip .


Download metadata

Metadata files can be downloaded as follows:

Version history

v1: inference carried out during April 2021 on imagery covering 19.4M km2 of Africa.