Water impermeable surfaces identified by artificial intelligence in the Helsinki metropolitan area

A spatial dataset describing the impermeable ground surface of the Helsinki metropolitan area produced with the help of artificial intelligence. The data is based on the interpretation of ortho-air images and point clouds using a method based on convolution euronets. The starting material for the interpretation was the National Land Survey’s orthophotos (50 cm) and point clouds (5p/m²) from 2020. The data is available in GeoTIFF format as 1 km*1 km rasters in the ETRS-TM35 coordinate system. Rasters have a pixel size of 20 cm and their pixel values represent the probability of water impermeable ground (asphalt/concrete/stones/buildings). In rasters, pixel values range from 0 to 254. The probability as a percentage can be formed 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, an impermeable ground surface. [sample image](https://avoidatastr.blob.core.windows.net/avoindata/AvoinData/9_Kartat/Maanpeiterasterit/vlp_esim_kuva_mml_orto_300_pienennetty.png “Sample image_Water_non-permeable_surface”) The survey of the impermeable surface has been produced by Scalgo ApS as part of the LaserVesi project, where the Helsinki Metropolitan Area served as a pilot area for national equivalent data. A similar method has been produced for HSY to map [the presence of bare soil (sand/sand)](https://www.hsy.fi/ymparistotieto/avoindata/avoin-data---sivut/tekoalylla-tunnistettu-paljas-maa-paakaupunkiseudulla/) in the Helsinki metropolitan area. Both materials have been produced as separate products and with their own designs. Therefore, the results show areas where the probability of both water impermeable surface and bare ground is more than 50 %. The map leaf distribution of rasters corresponds to the National Land Survey of Finland’s point clouds (2020). — [map magazine index (link to HSY map service)](https://kartta.hsy.fi/?zoomLevel=3&coord=25493699.370800566_6680845.766357424&mapLayers=654+100+default,741+100+tekoaly_vetta_lapaisematon_pinta_2021,739+100+tekoaly_indeksi_2021&uuid=508752a1-2d1e-4011-a0f7-a96e857fff64&noSavedState=true&showIntro=false) — [map magazine index (shp)](https://avoidatastr.blob.core.windows.net/avoindata/AvoinData/9_Kartat/Maanpeiterasterit/Indeksiruudukko_tekoalylla_tunnistetut_maanpeiteaineistot.zip) **[Short method description for mapping of impermeable surfaces](https://avoidatastr.blob.core.windows.net/avoindata/AvoinData/9_Kartat/Maanpeiterasterit/LaserVesi%20Documentation.pdf)** (in English). The vector-formal material displayed in the map service and interface has been modified for visualisation in such a way that: — only the objects of the water impermeable surface according to the modelling are included in the dataset — the external demarcation of the sites has been generalised — the material is distributed according to the map tiles, which causes artificial discontinuities between objects. For analyses, we recommend using the original raster material, which is available by requesting HSY. If you only want a part of the area, you can specify the map sheets you want in the request. Material requests: [email protected]. **[Data preview in HSY map service](https://kartta.hsy.fi/?zoomLevel=3&coord=25494883.370800566_6679117.766357424&mapLayers=654+100+default,741+100+tekoaly_vetta_lapaisematon_pinta_2021&uuid=508752a1-2d1e-4011-a0f7-a96e857fff64&noSavedState=true&showIntro=false).**