One continuously operating GPS station was installed up on Niwot ridge in early September. PI Kristine Larson will be using the data from the site to determine if GPS antennas (set in standard geodetic orientations) will be suitable for measuring changes in snow depth. These changes can be tracked in the corresponding multipath modulation of the GPS signal.
The implications of this study are far reaching. If geodetic monuments can be shown to reliably infer snow depth, then it is possible that the many, already operating, PBO GPS sites could serve as a real time snow network.
Other types of ground based snowpack telemetry networks already exist. However, these lack good spatial resolution and may not adequately represent areas of interest due to the fact that changes in elevation, wind distribution and avalanching cause snow coverage to vary greatly. The benefit of using GPS would be a greater measurement footprint per site as well as greater ease of use and minimal costs (since so many GPS stations already exist in snowy areas).
Snow depth, or, more importantly, Snow Water Equivalence (the product of snow depth and density), is vital to hydrological studies because it represents the amount of water available for runoff. This is essential for the management of water supply and flood control systems.
The antenna monument is a custom design that stands three meters high. It is constructed in the style of an SDBM, with additional supports to stabilize the extra tall center leg. The height of the monument will help keep the antenna (a Trimble Zephyr Geodetic) well above the surface of the snow throughout the winter. A small enclosure, approximately 100 feet south of the monument, houses a Trimble NetRS receiver. The device receives power from a small hut, 250 feet to the south of the enclosure. Ethernet cable is also run to the hut, where it is connected to a data radio which relays to a nearby internet connection.
Figure 1 - The extra tall, custom designed antenna monument at Niwot Ridge. Typically, the legs of a GPS monument are grouted into rock in pre-drilled holes. However, no bedrock exists in the area of study on the ridge. Thus, the rods were driven into the ground until refusal with a jackhammer
Last modified: Sunday, 11-May-2014 18:00:42 UTC