Snow

 

Although the results from our GPS snow sensing method are very promising, it doesn’t work well when trees are too close to the receiver.

  1. A.GPS SNR measurements observed at the Marshall GPS site on two consecutive days after the direct signal component has been removed. Red is used to indicate data before snow falls.  Approximately 35 cm of snow had fallen when the black trace was observed.

  2. B. Model predictions for no snow on the ground (red), and 35 cm of snow (black) using an assumed density of 240 kg/m3.

The effects of snow on reflected GPS signals can be directly related to snow depth since the multipath frequency is controlled by the distance between the antenna and the snow surface. Both SNR observations and an electrodynamic forward model show this relationship (see below).  Validation efforts are ongoing.

Shown above is one of our GPS sites for snow sensing.  It is hosted by the Niwot Ridge LTER.  The GPS data from this site are publicly available from UNAVCO.  Results for our first winter season are shown below (additional photo).

We are grateful to Trimble Navigation for loaning us a receiver to use at Niwot Ridge.