Project Lead: Kamron Ebrahimi
Mechanical Design: Andrew Brown
Software Architecture: Blake Hudson
Team Members on Leave: Grayland Lunn, Marrissa Kwon
Slide Sentinel is a monitoring system currently being designed to detect surface level shifts on known landslides for analysis and alerts. The system utilizes precise acceleration and relative positioning data from an accelerometer and RTK GPS receivers to detect subtle changes in sensor position within 1cm target precision due to land movement.
The Slide Sentinel project offers landowners a low-cost alternative to commercial equipment. With a network of remote low-power sensors, we can detect fast linear slides, and eventually slower soil movements such as creep. Sensor nodes transmit three-dimensional acceleration, Real Time Kinematic (RTK) GPS coordinates, and sudden shift alerts to a common satellite base station where they are logged to an online spreadsheet to be processed remotely and displayed in real time to a Google map.
Provide reliable position and orientation data from multiple nodes in a remote network
Provide alerts in case of catastrophic surface-level shifts
Use low-cost, low-power micro-electromechanical systems (MEMS) to keep cost to a minimum
Maintain low power budget to leave sensors in the field for up to 3 months, keeping technicians out of harms way
Upload sensor data to the cloud for knowledge on network status and differential monitoring
The Slide Sentinel utilizes a star network topology. A single hub unit, equipped with RTK GPS chip, an Iridium satellite module and a long distance, high-performance radio, sends correctional RTK data to every listening node in the network. Any node within the radio range of the hub can receive correctional data and can determine its exact location. In this fashion the Slide Sentinel architecture heavily resembles the classic client, server architecture seen in many web applications. Rovers within the network wake at a periodic interval, perform RTK resolution, send the hub the best calculated position, then fall back asleep to conserve power.
To ease in the visualization of collected data during deployments, the Slide Sentinel comes equipped with a software infrastructure hosted in the cloud to log data live to a Google spreadsheet and visualize the logged locations on a Google maps.
Coupled with the Google spreadsheet, the map provides the perfect visual interface for user data. The team wants to build the client portal out to contain information about the health and status of nodes within the network. The above spreadsheet contains data from the local deployment.
The above screenshot depicts markers displayed on a Google map illustrating the locations of the node.
Field testing thus far has provided insight into three main sub-systems in need of further development.
To date, the system has not been tested with more than one node in the network. Testing and building this feature out will be a top priority during this next development phase. We are aiming for every hub in the network to service upwards of ten or more rovers.
Rover power grid and enclosure
Rovers are designed to survive a minimum of 1 month deployments, though the system should be able to last without need of service for several months. This raises some interesting design considerations regarding the power grid and form factor on the node. We are currently looking at different enclosure designs, solar panels and battery options to make these units lighter, easier to deploy, and more reliable in extreme weather conditions. This development goal will require the design of both a PCB and experimentation with different 3D printed enclosures.
The ability to send remote configuration data to the hub unit and tune the upload frequency is already developed, however we want to see this functionality extended. Ideally a user could send a command to the satellite modem on the hub unit which could target and configure specific rovers within the network. For example, if a user wanted the rover with ID 1 to wake on a more frequent interval and provide more verbose data-logging they could simply send a satellite request and the configurations would touch the node on its next wake cycle.
Slide Sentinel is scheduled to deploy on a known landslide in the Alsea area on April 9th. Leading up to this deployment the team is extensively testing the system for robustness and measurement quality. From field test data on a 4 day local deployment, RTK resolutions occur approximately 70% of the time. This is super exciting to see the system working live out in the environment and data being collected and monitored throughout the entire pipeline.
HARDWARE LINKS AND DATASHEETS
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Tapley, B. D., & Kim, M.-C. (2001). Applications to geodesy. In L.-L. Fu & A. Cazenave (Eds.), Satellite altimetry and Earth sciences: A handbook of techniques and applications(pp. 371–406). San Diego, CA: Academic.
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