The Forest Carbon Monitoring project is gearing up towards the demonstration phase. As discussed in the previous blog, we are currently very busy with the algorithm tests, aiming to select the best algorithm and data combinations for the demonstration cases. At the same time, we have been preparing the datasets for the continental demonstration. For the past two months, massive Sentinel-1 and Sentinel-2 pre-processing tasks have been run on the Forestry TEP online platform.
The GAMMA Remote Sensing commercial Sentinel-1 pre-processing software package was implemented on the Foresty TEP platform. This software was used to pre-process all Sentinel-1A dual-polarization (VV/VH) IWS mode observations over Europe for 2020 and 2021. The pre-processing used ground-range projected images of the SAR backscatter intensity as input and resulted in a stack of terrain geocoded, radiometrically calibrated and co-registered Sentinel-1 observations for the two years. Over 50 000 images were processed, requiring over 50 000 CPU hours effective processing time. These datasets are used as input in the BIOMASAR approach to create two European wide growing stock volume and biomass maps in the European demonstration.
For the Sentinel-2 pre-processing, Terramonitor implemented their cloud free image compositing algorithm to the Forestry TEP platform. This algorithm was used to create two multi-temporal composite image mosaics over Europe for 2020 and 2021 (Figure 1), both covering 744 Sentinel-2 tiles. For each tile, imagery from the 15th June to 15th September were used, except for areas north of 62° N, where only images from 15th June onwards were used. The compositing algorithm evaluated each pixel according to four criteria: cloudiness, resemblance to usual pixels observed in the location (based on a reference mosaic), haze and shadows. A weight was then given for each pixel according to the four criteria. These weights were used to average the observations given as input and produce the final image. The resulting cloud free mosaics over Europe will be used in the European demonstration to detect changes between 2020 and 2021 with the Autochange algorithm.
The AFRY Smart Forestry team and VTT are currently working on the implementation and modifying the processing services and pipelines for the continental and other demonstrations into Forestry TEP. We aim to be ready to start the demonstrations on time from July onwards.
Figure 1. 2021 Sentinel-2 cloud free composite image mosaic. Insets around 3 km x 3 km in size.