[Map,42K,InlineGIF]
Figure 1.
Existing and planned GPS stations in and around Yellowstone National Park, 1999

The first continuous GPS station in Yellowstone National Park was installed in 1997 by the University of Utah and UNAVCO at Lake, Wyoming, near the outlet of Yellowstone Lake. Additional stations were added in 1998 near Yellowstone National Park headquarters in Mammoth, Wyoming, and northeast of Hamer, Idaho, with funding from the National Science Foundation. The USGS Volcano Hazards Program funded installation of 3 additional stations in September 1999: near White Lake, in Hayden Valley, and near Old Faithful. Site selection was based on results of a recent synthetic aperture radar interferometry study, which revealed two sources of uplift and subsidence within Yellowstone caldera (Wicks, Thatcher, and Dzurisin, Science, v. 282. pp. 458-462, October 16, 1998). All 6 existing stations include Trimble 4000SSi receivers and choke ring antennas. The Lake, Mammoth, Hamer, and Old Faithful stations use AC power, while the White Lake and Hayden Valley stations are powered by solar panels and batteries.

The White Lake and Hayden Valley stations are located in the Yellowstone backcountry, where they are subject to harsh Rocky Mountain winters with local snow accumulation exceeding 2 meters. With this in mind, we designed a special GPS monument for the backcountry sites that includes a 12-foot-long, 1.875-inch-diameter Invar rod surrounded by a concrete pillar for protection from bison, bear, and elk (Fig.2). The Invar rod is attached with expanding cement to the lower 2 foot section of a 4-foot-deep hole drilled in bedrock. A loose-fitting PVC tube is placed around the rod before the tube is encased in cement. Thus, the choke ring antenna at the top of the rod is mechanically isolated from everything but the rod itself and the lower 2 feet of the hole, and the rod is thermally insulated from the upper 2 feet of the bedrock by a thin column of air.

[Graphic,19K,InlineGIF]
Figure 2.
Schematic diagram of a GPS monument designed to keep the receiver above snow and afford protection from large animals in Yellowstone National Park.

Terrain differences between the two backcountry sites led to different layouts of the electrical, telecommunications, and GPS components of the stations. At White Lake, the GPS monument was coupled to solid bedrock in an open area approximately 100 meters from the forested crest of a small hill (Fig. 3). The solar panels were mounted on a 5 meter high tower in the open area, but closer to the crest of the hill (Fig. 4). An enclosure containing the GPS receiver and radio modem (Fig. 5) was mounted near the base of a tree at the top of the hill, and the telecommunications antenna was mounted near the top of the tree, with line of sight to Mount Washburn (Fig. 6). The same monument design was used at the Hayden Valley site, but in this case the solar panels, receiver enclosure, and solar panels were all mounted on a tower that provided line of sight to Mount Washburn (Fig. 8).

[Image,52K,JPG]
Figure 3.
White Lake GPS monument.

[Image,54K,JPG]
Figure 4.
White Lake instrument enclosure, including Trimble 4000SSi receiver, FreeWave radio modem, timer to turn modem on and off once/day, and lightning protection.

[Image,82K,JPG]
Figure 5.
White Lake solar panel tower and battery enclosure (partly buried culvert section, lower left).

[Image,75K,JPG]
Figure 6.
White Lake communications antenna mounted in tree to reduce visual impact.

[Image,85K,JPG]
Figure 7.
Hayden Valley GPS monument.

[Image,71K,JPG]
Figure 8.
Hayden Valley instrument enclosure, solar panels, communications antenna, and battery enclosure. Monument is barely visible in the distance, near bottom of channel midway between worker and instrument enclosure (shoulder level, directly behind partly buried battery enclosure).

The backcountry stations record GPS phase data for 8 hrs/day, while the Old Faithful station operates 24 hrs/day. The Old Faithful data are downloaded once/day via a telephone modem. Data from the White Lake and Hayden Valley stations are telemetered to Mount Washburn by FreeWave radio modems and then downloaded once/day via a telephone modem. Results will be posted on the Web as they become available.

-- Dan Dzurisin, Project Chief, USGS/Cascades Volcano Observatory, October 1999

Return to:
[Yellowstone GPS Network Menu] ...