Impervious surfaces identified by artificial intelligence in Helsinki Metropolitan Area

A comprehensive geospatial dataset describing impermeable land surfaces in the Helsinki metropolitan area, produced with the help of artificial intelligence. The data is based on the interpretation of ortho-aerial images and point clouds using a method based on convolution neural networks. The interpretation was based on orthoimages (50 cm) and point clouds (5p/m2) from the National Land Survey of Finland in 2020. The material is available in Geotiff format as 1 km * 1 km rasters in the ETRS-TM35 coordinate system (EPSG:3067). The rasters have a pixel size of 20 cm and their pixel values represent the probability of an impermeable surface (asphalt/concrete/stones/buildings). In rasters, pixel values range from 0 to 254. Probability as a percentage can be obtained by dividing the pixel value by 254 and multiplying by 100. In practice, pixels with a value of 127 or above are, according to the modelling, impervious to water.  The mapping of the impermeable surface has been produced by Scalgo ApS as part of the LaserVesi project, in which the Helsinki metropolitan area served as a pilot area for national equivalents. A mapping of [the presence of bare land (sand/gravel)] (https://www.hsy.fi/ymparistotieto/opendata/open-data--pages/artificial intelligence-identified-bare-country-parity-region/) in the Helsinki Metropolitan Area has been produced for HSY using a similar method. Both datasets have been produced separately from each other and with their own models and emphasis. As a result, the results show areas where both impermeable surfaces and bare soils are more than 50% likely to occur. The map sheet distribution of the rasters corresponds to the map sheet distribution of the Finnish National Land Survey's point clouds (2020). - [Map sheet index (link to HSY's map service)](https://kartta.hsy.fi/?zoomLevel=3&coord=25493699.370800566_6680845.766357424&mapLayers=654+100+default,741+100+tekoaly_vetta_lapless_pinta_2021,739+100+tekoaly_ Index_2021&uuid=508752a1-2d1e-4011-a0f7-a96e857fff64&noSavedState=true&showIntro=false) - [Map sheet index (shp)](https://avoidatastr.blob.core.windows.net/opendata/OpenData/9_Maps/Land cover rasters/Index grid_tekoalylla_identified_land cover data.zip) **[Short methodological description of the impermeable surface survey](https://avoidatastr.blob.core.windows.net/opendata/OpenData/9_Maps/Land cover rasters/LaserVesi%20Documentation.pdf)**. The vector-based material displayed in the map service and at the interface has been modified for visualisation in such a way that: - only the impermeable surface objects according to the modelling are included in the data - the outer boundaries of the sites have been generalised - the material is distributed in accordance with map tiles, which causes artificial discontinuities between objects. For the analyses, we recommend using the original raster data, which is available by requesting it from HSY. If you only want a part of the area, you can specify the map sheets you want in the request. Requests for materials: avoindata@hsy.fi. **[Preview of the material in the HSY map service](https://kartta.hsy.fi/?zoomLevel=3&coord=25494883.370800566_6679117.766357424&mapLayers=654+100+default,741+100+tekoaly_vetta_lapless_pinta_2021&uuid=508752a1-2d1e-4011-a0f7-a96e857fff64&noSavedState=true&showIntro=false).**