Low-cost GNSS-Reflectometry R&D

Application of GNSS-R for wetlands mapping using the Android phone device and u-blox GNSS module

https://gpscat.ca/2022/09/10/application-of-gnss-r-for-wetlands-mapping-using-the-android-phone-device-and-u-blox-gnss-module/

Wetlands are areas that are inundated or saturated either permanently or intermittently and support vegetation types that are adapted to saturated conditions. Mapping the wetlands is very important in identifying mosquito breeding sites along the river floodplain areas on different water levels. The GNSS-R as passive remote sensing technique can improve the mapping of wetlands in combination with the RGB and CIR cameras and provide better image interpretation and overall results. L-band signals transmitted from the GNSS constellations are less obscured by high biomass vegetation which can be found in the floodplain areas. 

The Android phone device uses the custom adapted GNSS-R Logger application based on the open source code from Google GNSSLogger App. The application is installed on phone with Android 11 operating system version, which is covered with the PCB plate for blocking the direct signal reception. The first test was conducted together with the RGB camera image acquisition from the helicopter with Above Ground Level of 250 meters over a wetland area consisting of various vegetation type covers. GNSS-R Logger app recorded raw GNSS data at L1 frequency bands of GPS and GLONASS satellites. The second test was also conducted from the helicopter with Above Ground Level of 400 meters over the two rivers. 

The further tests will also include the GNSS-R receiver based on u-blox 7 GNSS module with the laptop computer as a data logger, and also taking into consideration the distribution of GNSS satellites before the flight.

Prototype GNSS-R devices. Android phone device and u-blox GNSS module. 

C/N0 carrier-to-noise density of GPS 26 satellite with an elevation of 25 degrees. The red and orange dots with higher values represent the pass over the clear water and wetland. The image is an RGB orthophoto image with a spatial resolution of 9cm/pixel. 

C/N0 carrier-to-noise density of GPS 18 satellite with an elevation of 80 degrees 29.07.2022. The  red high values represent the pass over the water. The pass over the little island in the river can be seen with short low values signal appearing. The background image is RGB Sentinel 2 image 23.07.2022. 

C/N0 carrier-to-noise density of GPS 18 satellite with an elevation of 80 degrees 29.07.2022. The  red high values represent the pass over the river. The background image is RGB Sentinel 2 image 23.07.2022.