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AXTracker: An Inexpensive Satellite Transmitter
for Sensing Changes at Remote Locations

Field Applications

The AXTracker was originally developed to report GPS location and provide alarm notifications for cargo trucks. Besides vehicle location, the AXTracker was designed to have various sensors or alarms to track vehicle conditions, such as temperature and the status of doors (open or closed). These sensors and alarms can serve different purposes. For instance, the AXTracker could be used to monitor environmental conditions, such as water levels and soil, water, and air temperatures or for alarm notifications at remote facilities. Temperature is the only environmental sensor that has been configured for the AXTracker, but any alarm sensor with an on/off contact could trigger the device.

Environmental Monitoring

Monitoring remote sites can be expensive and potentially hazardous. For example, when planting sites are being monitored for reforestation, several trips to the planting site may be needed to ensure that the snow has melted and soil temperature and moisture are optimum for successful planting. Depending on the location of the planting site, these trips may be time consuming and also difficult or dangerous.

The AXTracker system with the dual temperature probe can be an inexpensive method of monitoring planting sites remotely. One temperature probe can be placed just under the soil surface to monitor soil temperature. The other sensor can be mounted just above the soil surface to monitor snowmelt (figure 2). When snow surrounds the upper sensor, the temperature should stay at about 32 °F. As the snow melts, exposing the sensor, temperatures should range above and below 32 °F. MTDC conducted successful field tests of temperature sensors to monitor snowmelt during the winter and spring of 2004.

Photo of two AXTracker units positioned on a snowy hillside in a forested area.
Figure 2—Two AXTrackers, one measuring temperatures just under the soil surface
and another measuring temperatures just above the surface, can provide an
inexpensive method for tracking soil temperature and snowmelt in remote regions.

The AXTracker can be programmed to send a report at specific intervals (from 15 minutes to 45 days) or to send an alarm at a programmed temperature. Either approach can help keep transmission costs low. Figure 3 shows a typical Web page with a temperature table and location information from an AXTracker. This is just one example of using the AXTracker for environmental monitoring. Any environmental sensor with an on/off contact or alarm could be used to monitor conditions in the environment.

Graph depicting the temperature profile recorded from December 1, 2004 to March 8, 2005. A green line indicates average temperatures, a blue line indicates low temperatures, and a red line indicates high temperatures.
Figure 3—This graph shows the daily low, average, and high temperatures
for a temperature probe at the surface of the ground. The sensor was exposed until a
snowstorm in early December when the low, average, and high temperatures were
essentially equal. The snow melted in late February, exposing the sensor to
daily variations in temperature with this installation. The AxTracker did not accurately
measure air temperature because the probes were exposed to direct sunlight.

Remote Facility Alarm Notification

Many of the 40,000 buildings and other facilities in the National Forest System are in remote areas where normal very high frequency (VHF) radio or cellular systems are unavailable or unreliable. Such facilities may include municipal watersheds, electronic sites, dams, pipelines, powerlines, tank farms, fee collection sites, bridges, and gates. In remote areas, the AXTracker can provide a relatively inexpensive means for communicating any activity discernible by a sensor back to the appropriate forest office or employee. These activities include intrusions, thefts, broken water pipes—other possibilities are limited only by your imagination.

Vehicle Tracking

Because the AXTracker was developed as a fleet management tool, it is well suited for tracking Forest Service vehicles. A vehicle's GPS coordinates can be transmitted at regular intervals or in connection with a certain event, such as when the back door of the vehicle opens, or when the vehicle starts or stops moving. It is easy to configure one alarm input as a "panic" button that transmits a distress signal, along with GPS coordinates. Another input can be configured to transmit a restore or All okay signal.

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