Sentinel-2 satellite image mosaics 2017-2021 (S2GM) – Sentinel-2 satelliittikuvamosaiikki 2017-2021 (S2GM)

Sentinel-2 satellite image mosaics are produced from data provided by MultiSpectral Instruments (MSI) onboard Sentinel-2A and -2B satellites. These mosaics have been produced using previous version of Sentinel-2 Global Mosaic-service (https://s2gm.sentinel-hub.com/) of Copernicus program of European Union. The value of pixel is the estimate of ground reflectance, multiplied by coefficient 10000. Mosaics contain following bands with central wavelength of bands:

* B02: Blue (492.4 nm)
* B03: Green (559.8 nm)
* B04: Red (664.6 nm)
* B05: Red-edge (704.1 nm)
* B06: Red-edge (740.5 nm)
* B07: Red-edge (782.8 nm)
* B08: Near infra-red (832.8 nm)
* B11: Middle Infrared (1613.7 nm)
* B12: Middle infrared (2202.4 nm)

The pixel size of all bands is 10 meters, in other words the 20 meter bands (B05, B06, B07, B11, B12) have been resampled to 10 meter pixel. The more detailed information about the bands can be found from https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi/resolutions/radiometric. Currently, 
there are no metadata image describing the acquisition date of selected pixel.

Processing

Steps of mosaicking process (https://usermanual.readthedocs.io/en/latest/) at Sentinel-2 Global Mosaic service are:

* Selection of Sentinel-2 images of chosen area of interest and time period.
* Atmospheric correction of images using Sen2cor-algorithm.
* Selection of the least different pixel of time period from a set of good pixels.
* Production of output mosaic with chosen bands, pixel size and coordinate system.

Tilewise mosaics are downloaded to local computer, where post-processing phase consists of merging of tiles to form bandwise mosaics, filling of gaps using neighboring values and coordinate transform to Finnish coordinate system TM35Fin (EPSG 3067). 

Download

Mosaics are available as bandwise and RGB-mosaics. RGB-mosaics are in false color combination, in other words band combination is

* 1: Band 8, Near infra-red
* 2: Band 4, Red
* 3: Band 3, Green

These mosaics are scaled to 8-bit numbers (0-255). Bandwise mosaics contain individual bands in 16-bit numbers and resampled to 10 meter pixel.

Following RGB quarter mosaics are available:
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20170701_20170930_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20180701_20180930_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20190401_20190630_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20190701_20190930_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200401_20200630_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200701_20200930_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20210401_20210630_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20210701_20210930_8bit.tif

Following RGB monthly mosaics are available: 
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200401_20200430_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200501_20200531_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200601_20200630_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200701_20200731_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200801_20200831_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200901_20200930_8bit.tif

Bandwise mosaics are available as:
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_band_time.tif

where

* band: b02, b03, b04, b05, b06, b07, b08, b11 or b12
* time: 20170701_20170930, 20180701_20180930, 20190401_20190630, 20190701_20190930, 20200401_20200630, 20200701_20200930, 20210401_20210630, 20210701_20210731 or 20210701_20210930

This Syke’s dataset can be used according to open data license (CC BY 4.0)

Sentinel-2 satelliittikuvamosaiikki 2017-2021 (S2GM)

Sentinel-2 satelliittikuvamosaiikit perustuvat Sentinel-2A/2B satelliittien MultiSpectral Instrument (MSI) kuvausinstrumenttien ottamiin kuviin. Mosaiikit on tuotettu Sentinel-2 Global Mosaic palvelun ensimmäisellä versiolla (https://s2gm.sentinel-hub.com/) joka on osa Euroopan Unionin Copernicus ohjelmaa. Mosaiikin kuvapikselin arvo on maanpinnan heijastussuhteen estimaatti, kerrottuna kertoimella 10000. Mosaiikeissa on seuraavat kanavat (suluissa kanavan keskikohdan aallonpituus):

* B02: Blue (492.4 nm)
* B03: Green (559.8 nm)
* B04: Red (664.6 nm)
* B05: Red-edge (704.1 nm)
* B06: Red-edge (740.5 nm)
* B07: Red-edge (782.8 nm)
* B08: Near infra-red (832.8 nm)
* B11: Middle Infrared (1613.7 nm)
* B12: Middle infrared (2202.4 nm)

Kaikkien kanavien pikselikoko on 10 metriä, eli 20 metrin kanavat (B05, B06, B07, B11, B12) on uudelleennäytteistetty 10 metrin pikselikokoon. Tarkemmat tiedot MSI-instrumentin kanavista löytyvät osoitteesta https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi/resolutions/radiometric. Metatietomosaiikkia, eli mosaiikki joka kertoisi pikseleiden kuvaushetket, ei ole tuotettu.

Prosessointi

Sentinel-2 Global Mosaic palvelun osat (https://usermanual.readthedocs.io/en/latest/) ovat:

* Valitun alueen ja ajanjakson Sentinel-2 kuvien valinta.
* Kuvien ilmakehäkorjaus Sen2cor-algoritmilla.
* Mosaiikin pikselin arvoksi valitaan ajanjakson kuvien pikseleitä se joka poikkeaa vähiten muista.
* Tiilittäisen mosaiikin tuottaminen valituilla kanavilla, pikselikoolla ja koordinaattijärjestelmällä.

Tiilittäiset mosaiikit ladataan paikalliselle tietokoneelle jolla tehdään jälkiprosessointivaihe, eli tiilet yhdistetään kanavittaisiksi mosaiikeiksi, aukot täytetään naapuruston avulla ja tehdään koordinaattimuunnos suomalaiseen koordinaatistoon (TM35Fin, EPSG 3067). 

Tarkempia tietoja Sentinel-2 Global Mosaic-palvelusta löytyy osoitteesta https://s2gm.sentinel-hub.com/documentation.

Saatavuus

Mosaiikit ovat saatavilla sekä kanavittaisina että RGB-mosaiikkeina. RGB-mosaiikit ovat vääräväriyhdistelmiä, eli kuvan kanavat ovat

* Kanava 8, lähi-infrapuna
* Kanava 4, punainen
* Kanava 3, vihreä

Nämä mosaiikit on skaalattu 8-bittisiksi lukualueelle 0-255. Kanavittaiset mosaiikit käsittävät yksittäiset kanavat 16-bittisillä numeroilla 10 metrin pikselikoolla.

Ladattavissa olevat neljännesvuosittaiset RGB-mosaiikit:
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20170701_20170930_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20180701_20180930_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20190401_20190630_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20190701_20190930_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200401_20200630_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200701_20200930_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20210401_20210630_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20210701_20210930_8bit.tif

Ladattavissa olevat kuukautis-RGB-mosaiikit:
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200401_20200430_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200501_20200531_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200601_20200630_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200701_20200731_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200801_20200831_8bit.tif
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_b080403_20200901_20200930_8bit.tif

Kanavittaiset mosaiikit:
* https://pta.data.lit.fmi.fi/sen2/s2m_s2gm_mos/pta_sjp_s2gm_band_time.tif

jossa
* band: b02, b03, b04, b05, b06, b07, b08, b11 tai b12
* time: 20170701_20170930, 20180701_20180930, 20190401_20190630, 20190701_20190930, 20200401_20200630, 20200701_20200930, 20210401_20210630, 20210701_20210731 tai 20210701_20210930

Aineisto kuuluu SYKEn avoimiin aineistoihin (CC BY 4.0).

Sentinel-2 satellite image mosaics are produced from data provided by MultiSpectral Instruments (MSI) onboard Sentinel-2A and -2B satellites. These mosaics have been produced using Sentinel-2 Global Mosaic-service (https://s2gm.sentinel-hub.com/) of Copernicus program of European Union. The value of pixel is the estimate of ground reflectance, multiplied by coefficient 10000.

Organization: Suomen ympäristökeskus (Syke)