Abstract

Statistics Finland's (stat.fi/index_en.html) Construction and Housing Production statistics publishes information on started and completed construction projects on a voluntary basis. The statistics obtains weekly construction project data from the Digital and Population Data Services Agency. This information is reported by the municipalities and it accumulates with a delay. Due to the delay, the latest month's statistics are always based on incomplete data at the time of production.

Statistics Finland started a Proof of Concept (PoC) in the beginning of 2024 to explore if satellite data together with building permit data can specify the month the construction began in more timely fashion. We used European Space Agency (ESA) Sentinel-2 visible band data and Sentinel-1 synthetic-aperture radar (SAR) data for four building sites with 10 buildings that were either high rises or large commercial buildings. Time range for observation was selected using building permit data. A change in RGB values within each band in Sentinel-2 data and change in polarization in Sentinel-1 SAR data around the time of reported start date would indicate the beginning of construction. Sites were observed using Copernicus and EO Browsers for Sentinel-1 data and downloaded images from Sentinel Hub Catalogue API for Sentinel-2 data. The latter were analyzed using R.

Results of the PoC are promising. Construction start month could be assigned for all examined sites. However, the variability in surrounding land cover, especially in densely constructed city areas, may be a challenge when trying to distinguish the beginnings of a construction. Moreover, large machines and movable site huts may appear like newly erected buildings in the data. Clouds and snow are also issues not tackled during this PoC but ones that may cause challenges.