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SNOW MONITORING USING GNSS-R TECHNIQUES
§Remote Sensing Lab, Dept. TSC, Building D3, Universitat Politècnica de Catalunya, Barcelona, Spain and IEEC CRAE/UPC
FUNDAMENTALS OF THE INTERFERENCE PATTERN TECHNIQUE
THE ALGORITHM FOR RETRIEVAL• From theory the notches evolution dependence on the elevation angles is found, fig. 6.
SNOW MONITORING USING GNSS-R TECHNIQUES
•For the first DoY of measurement, select the notches in the received powers sequences and compute the snow thickness based on fig. 6. • In order to solve the uncertainly, assume that 5 cm is the snow thickness (known from ground-truth), and choose the nearest solution.• The solution for each satellite is stored for being used as the calibration measurement.• From that measurement the evolution of notches is tracked. The criterion to solve the uncertainty, when processing the following measurement days, has been stated to be that snow falling affects all the surface in the same way and then the most probable solution obtained from fig. 6 is selected.
Figure 6. Theoretical evolution of notches. The notches position and the number of them (each black line defines the evolution of one notch) describe the snow thickness. The snow layer has been simulated considering a snow wetness volume of 2% and a snow density of 8 %.
Figure 11. The SMIGOL-Reflectometer measured powers and the simulated powers by applying the algorithm for (a) satellite 16 on DoY = 303 and (b) satellite 31 on DoY = 344.
THE PROCESSING
• The SMIGOL-Reflectometer measurements were processed and the algorithm to compute the equivalent snow thickness was applied to the measurements.
• Notches were selected and their position was analyzed, following fig. 6 and the criterion stated in the algorithm.
• The Interference Pattern Technique and the SMIGOL-Reflectometer are able to monitor the snow thickness variations.
• The retrieval algorithm developed is based on the position of notches, plus a tracking function that daily analyzes the movement of that notches in the received power plots.
• The correlation values of the measurements with the ground-truth in different points of the surface show that the technique can monitor changes in the snow thickness.
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SNOW MONITORING USING GNSS-R TECHNIQUES
This work has been sponsored with funds from the Plan Nacional del Espacio of the Spanish Ministry in the frame of the project with reference ESP2007-65567-C04-02 and also by funds from the project with reference AYA2008-05906-C02-01/ESP and the project AYA2010-22062-C05-05/ESP.