Validation approach following widely accepted protocols will be prepared at first part of the task realisation. The test sites for validation purposes have been selected representing representative for various crops and grasslands and soil moisture conditions in Poland. In-situ validation measurements took into account satellites overpasses (Sentinel2, Proba-V) phenology and types of land monitoring products.
Every year, the agriculture test site has been situated at the western part of Poland. The grasslands area at the wetlands was situated at the eastern part of Poland. The choice of these locations has been done in regard to the knowledge about the test sites where other measurements have been done in the past. Also the agriculture plots are large and there is the variety of crop types.
Grasslands plots which were covered by measurements have been sitauted at Biebrza Wetlands.
Sentinel-2 – time of -10 days.
Wielkopolska – agriculture site – Track 122
Biebrza – wetlands site – Track 036
Proba-V (spatial resolution 100 m – 3 times a week & 300 m – every day).
During the fields campaigns the same measurements have been done at Biebrza test site as at Wielkopolska test site.
For ground measurements the following instruments have been used:
- Spectral responses by the ASD FieldSpec 4 Hi-Res (last year – since 8 of June);
- Leaf Area Index (LAI) (with LAI-2000 and LAI 2200 Plant Canopy Analyser);
- Soil moisture (with TRIME Field Measurement Devices);
- Wet and dry biomass (in a laboratory, from samples collected at measurement plots from the area of 0.4 x 0.4 m);
- Radiance temperature (with EVEREST AGRI-THERM II);
- APAR (with AccuPar instrument);
- Chlorophyll (with FieldScout CM 1000 Chlorophyll Meter);
- Chlorophyll fluorescence (with Pulse Modulated Chlorophyll Fluorometer OSP5p+, since 18th of June 2017);
- Carbon balance (with chamber method and Eddy-Covariance method);
- Type of vegetation cover and its development stage;
- Height of vegetation.
Meteorogical data also was used. The meteorological stations on both test sites have the following sensors:
- air temperature and humidity;
- an anemometer recording wind speeds and directions;
- net radiometer;
- pyranometer measuring solar radiation in a range of spectra response from 305 to 2800 nm;
- pyrgometer measures far-infrared radiation in a range of spectra response from 4500 to 50000 nm;
- rain gauge;
- leaf wetness sensor measuring dielectric constant of a zone approximately 1 cm from the upper Surface of the sensor;
- NDVI sensor.
For the transect measurements of spectral response 350-2500 nm, the following measurements were done: reflectance, LAI, SEL, APAR, chlorophyll, soil moisture, surface temperature, air temperature, height vegetation and phonological stage. Photo was added to each point.
In 2017 year the method of doing the transect have been improved compared to 2016 year (Camacho et al., 2015). In order to better characterize each pixel resolution (10 m, 20 m and 60 m – Sentinel-2) was more density of points.
2016 year: The transect consists of 7 – 9 measurement points. Distances between points were ca. 50 – 80 m. The transect in a straight line.
- Sentinel-2: only one measurement point in each pixel resolution [Fig. 3].
- Proba-V: only two or one measurement points [Fig. 4].
2017 year: The transect consisted of 11 measurement points. Distances between points were ca. 10 m. The transect in the shape of a cross.
Sentinel-2: one measurement point in 10 m pixel, two measurement points in 20 m pixel, ten measurement points in 60 m pixel [Fig. 5.]
- Proba-V: eight measurement points in 100 m pixel [Fig. 6].
Transects measurements were done in 2016 and 2017.