Sentinel 3 Validation in Inland Waters (GLaSS-S3VAL)
Peters, Steef1; Hommersom, Annelies1; Laanen, Marnix1; Poser, Kathrin1; Koponen, Sampsa2; Heege, Thomas3; Eleveld, Marieke4; Storm, Thomas5; Giardino, Claudia6; Reinart, Anu7; Philipson, Petra8; Odermatt, Daniel5; Ruescas, Ana5; Greb, Steven9; Yunlin, Zhang10; Dekker, Arnold11; Ghezegehn Ghebrehiwot, Semhar1
1Water Insight BV, NETHERLANDS; 2SYKE, FINLAND; 3EOMAP, GERMANY; 4VU-IVM, NETHERLANDS; 5Brockmann Consult, GERMANY; 6CNR, ITALY; 7Tartuu Observatory, ESTONIA; 8Brockmann-geomatics, SWEDEN; 9Wisconsin Department of Natural Resources, USA, UNITED STATES; 10Nanjing Institute of Geography and Limnology, CHINA; 11CSIRO, AUSTRALIA

It is estimated that today more than 8 million lakes larger than 1 ha, and more than 10 million km2 of wetlands exist worldwide. Due to their basic ability to retain, store, clean, and evenly provide water, as well as their distinct characteristics as still-water bodies, lakes, reservoirs and wetlands constitute essential components of the hydrological and biogeochemical water cycles, and influence many aspects of ecology, economy, and human welfare. Knowledge about the distributions and state of lakes, reservoirs and wetlands is therefore of great interest in many scientific disciplines (Lehner and Doell, 2004). Besides their regional significance, the state of global lakes is of particular interest for assessments of present and future water resources, for climate change modeling (global land surface parameterization, methane emissions), and for large-scale studies of the environment, biodiversity, health (spreading of water-borne diseases), and agricultural suitability (Voeroesmarty et al., 2010). The FP7 project GLaSS aims to use satellite water quality products derived from the Sentinel 2 and 3 (S2 and S3) satellites to set up innovative user-relevant value adding services on water quality in Europe's inland waters. The direct advantages of this approach is that the high overpass frequency of S3 and the high spatial resolution of S2, combined with their high spatial location accuracy will provide unprecedented monitoring capabilities. Earth observation (EO) technology allows us to monitor large water areas (from local to global scale) with systematic and cost-effective acquisitions. Salmaso and Mosello (2010) reviewed over 200 articles published in the field of limnology and draw the conclusion that synoptic analyses on a macro-regional scale are mandatory in this field. EO has been used to assess water quality parameters in several European lakes: Spanish reservoirs (Simis et al. 2007); Boreal lakes (Voutilainen et al. 2007; Paavel et al. 2007; Kutser et al. 2005; Philipson et al. 2003; Stroembeck and Pierson 2001); Perialpine lakes (Guanter et al. 2010; Odermatt et al. 2010; Odermatt et al. 2008; Albert and Peter 2006; Giardino et al. 2005; Oesch et al. 2005; Keller 2001); Italian lakes (Giardino et al. 2010; Bresciani et al. 2009; Giardino et al. 2007a); small lakes in England (Hunter et al. 2010a; George and Malthus 2001); and small lakes and reservoirs in Holland and Belgium (Van Mol and Ruddick 2005; Dekker et al. 2002; Dekker et al. 2001). Increased use in radiative transfer modelling and spectral matching algorithms has led to new remote sensing algorithms such as HYDROPT (Van der Woerd and Pasterkamp, 2008. The results of algorithms is dependent on quality of the input remote sensing data which is however dependent on aerosol retrieval and atmospheric correction over these lakes (Giardino et al., 2007).
The GLaSS-S3VAL team consists of renowned EO of inland water researchers and service providers from the following institutes and companies: Water Insight BV, SYKE, EOMAP, VU/IVM, Brockmann Consult, CNR, Tartuu Observatory, Brockmann Geomatics Sweden and the members of the international advisory board of the GLaSS project.

The approach taken:

1) GLaSS will build tools to handle the S3 data; this process will serve to validate the data format and distribution
2) Products from Algorithms developed in the GLaSS project and standard S3 products will be validated on the bases of field data: attention will be given to the validation of L2 reflectance and L2 water quality products in at least the following lakes:
1) Netherlands: Lake IJssel (IVM & WI)
2) Estonia: Lake Peipsi (TO)
3) Italy: Lake Garda (CNR)
4) Germany: Lake Constance (EOMAP)
5) Sweden: Lake Vanern (BG, CNR,)
6) Finland: Finnish Lakes (Syke)
7) ...additional Lakes to be determined later
Partners will carry out field campaign according to the standardized field protocols and data will be combined to the preferred database. Lakes are selected to represent various classes, status, management and importance to the socio-economic development. Partners will visit field campaigns in each test lake at least once during the project to exchange experience and specifically for intercalibration purposes. All partners participate in the MVT and are actively engaged in intercomparison activities whenever possible and appropriate. Most partners are already involved in MERMAID.