VolcanoSRI Deployments

There were two field deployments during the course of the VolcanoSRI project. These two field deployments were used to understand the varying environments the sensors nodes would be subjected to and to test their operation.
Tungurahua Volcano
Ecuador Deployment Team
Prototype Sensor Node
Node Locations

Tungurahua Deployment

To test the first generation sensor nodes, we traveled to the Tungurahua Volcano near Baños Ecuador and deployed six nodes in July, 2012. Tungurahua is a stratovolcano located 140 kilometers south of the capital Quito and one of the major volcanos of Chile. This field trip afforded us an opportunity to test under real field conditions. It also allowed us to gain first-hand experience of the conditions we would face in future larger scale deployments. The primary goal was to test whether our sensing hardware can record seismic signal.

Participants in this deployment included:

The field deployment was supported by Mario Ruiz of the Instituto Geofísico de la Escuela Politécnica Nacional in Quito.

The six prototype sensors deployed each consisted of an Android phone with an attached external board. The external board contained a 12 bit digitizer, signal amplifier and GPS receiver controlled by software running on the phone. Two of the sensors were deploy adjacent to the RUNTUN permanent monitoring stations. The RUNTUN station is located next to La Casa del Arbol. Two additional sensors were deployed approximately 1 km from the station to the east while the final two sensors were deployed several kilometers away to the west on the other side of the adjacent ridge.. During the 5-day deployment period the sensors near the RUNTUN station wer able to successfully record a seismic event 20km away.

The deployment faced several challenges. The first was the remote location. Only a few sites were accessible by road. Vast areas were only reachable via hiking on foot. Utilizing helicopters to assist during deployment was not feasible due to the altitude and the highly variable nature of the weather conditions. Teams must carry all the equipment in backpacks several kilometers to reach the deployment locations. Besides the distances that must be covered, working at high altitude (12,000 to 14,000 feet) presented its own challenges. From the sensor design standpoint, care must be taken to minimize the package weight. It was important for the teams to be able to maximize the number of packages carried on each trip so as to minimize the number of trips. The wet weather conditions presented the second challenge. Between fog, that commonly covered the volcano, and rains challenged the equipment packaging.

During this field trip, we experienced several of these challenges. During the first two days, the volcano was covered in fog and it rained heavily. This was a good test for the packages and the team. After two days under these conditions, the sensors were still functioning and were completely dry inside. Subsequently, it was discovered that the cases used were not strong enough to withstand rough handling. The thin material was easily cracked and the rubber seal did not seat properly to prevent moisture from entering.

Llaima Volcano
Array Placement
Llaima Sensor Node
In-Field Staging Prior to Deployment
Installed Base Station with Satellite Link
Installed Base Station with Satellite Link

Llaima Deployment

The second deployment was on Llaima Volcano located near Melipeuco, Chile. Llaima is one of the most active volcanos in Chile and is located 663 km southeast of Santiago. The primary goal of this deployment was to test the new generation of hardware over a long duration period. We deployed 16 new-generation nodes in January 2015, in a 800 by 1400m patch. The adjacent picture shows the deployment locations relative to the volcano summit and the terrain around the nodes. Llaima has an access road encircling it and the lower slopes can be reached using an off-road vehicle. With the varied terrain, it also provided a good field test of the node to node communications. The 16 nodes were deployed by three 2-person teams in one day. One team acted as a survey team establishing the final node locations. These were chosen based on topology to ensure that at least three other node locations were visible. In addition to the 16 sensor nodes, a base station with satellite link was deployed to provide communication with our server located in East Lansing, MI. The system ran from January 10th to March 25th, 2015.

Together with our sensor nodes, 26 traditional seismic stations were deployed across a broad geographic area surrounding the volcano, as shown in adjacent picture. These traditional stations were installed over a period of two weeks by four multiple-person teams. The number of people in each deployment team depended upon how far the equipment had to be carried from the nearest road. Two stations were transported on horseback.

Our nodes are composed of an Arduino Due processor mated with a custom board containing the specialized sensing components. The Arduino Due was chosen due to its computational power and the desire to use an existing design where possible. It contains an 84 MHz AMTEL 32 bit processor which is able to digitally filter a sample using a 204 order FIR filter and compute the STA/LTA ratio in 0.15 milliseconds. It can perform an ARAIC computation on a 16 second signal (1600 samples) in 3.9 seconds. With proper buffering this allows the node to easily handle a sample rate of 100 samples per second without losing samples. Sampling is performed using a 24-bit ADC fitted with an instrument amplifier to boost the signal from the seismic sensor.

For communication, a Digi International XBee-Pro 900HP 900 MHz RF module provides network communications. This module support DigiMesh network topology with a RF data rate of 200Kbps. %The maximum transmit power of this unit is 250 mW (24 dBm) and the receiver sensitivity is -101 dBm at 200Kbps. 900 MHz was chosen over 2.4GHz due to the reduced signal absorption in heavily wooded areas. The manufacturer claims the unit is capable of a line of sight range of 6.5 km with a 2.1 dB dipole antenna. This radio provides sufficient capability to allow a large number of nodes to exchange short messages, i.e. position information and event detection results. A GlobalTop Technologies, Inc. MTK3339 GPS chip provides geolocation information and global time along with a low jitter (<10 ns jitter) 1 pulse per second signal. This signal is used to synchronize the internal processor clock to global time. To mitigate the increased power consumption, control circuitry was included allowing the GPS chip to be powered down. A small coin battery is used to maintain the GPS memory during power down to allow quick restart when power is reapplied.

To power the nodes Sealed Lead Acid (SLA) batteries were chosen. While not necessarily having the highest energy density, SLA's have certain advantages over other choices. They are inexpensive, commonly available even in third world countries, easy to transport, operate over a wide temperature range and survive large numbers of charge/discharge cycles.