Life Under your Feet: A W ireless Soil Ecology Sensor Netw ork R. - PowerPoint PPT Presentation

Life Under your Feet: A W ireless Soil Ecology Sensor Netw ork R. Musaloiu-E † ., A. Terzis † , K. Szlavecz ‡ , A. Szalay * , J. Cogan * , J. Gray ◊ † Computer Science Department, JHU ‡ Earth and Planetary Sciences Department, JHU * Physics Department, JHU ◊ Microsoft Research EmNets 2006 Life Under your Feet 1

I n the Beginning… The Cast • An ecologist: Katalin Szlavecz • An undergrad student working • in a summer project: Joshua Cogan The Stage • The urban forest near the JHU • campus Off-the-self soil moisture and • temperature sensors A few Mica2 motes • The Goal • Test whether WSNs can be • used to collect soil monitoring data at spatial and temporal scales larger than that of data loggers EmNets 2006 Life Under your Feet 2

First Step The sensors were • thoroughly tested in the lab 2 out of 6 sensors • misbehaved Relatively precise (+/- • 0.5°C) … but offset of 1.5°C from • a NIST approved thermocouple. Next step: teach the motes • to play their part. EmNets 2006 Life Under your Feet 3

Second Step More actors: • CS faculty (Andreas Terzis) • CS grad student (Razvan Musaloiu-E.) • DB experts: Alex Szalay and Jim Gray • More setup: • MicaZ motes • MSSQL • Skyserver DB software • The goal • Build an end-to-end data collection • system EmNets 2006 Life Under your Feet 4

System requirem ents Measurement fidelity • All the raw measurements should be collected and • persistently stored Measurement accuracy and precision • Temperature data error < 0.5 C, volumetric moisture data • error < 1%. Fusion with external sources • Comparing measurements with external data sources is • crucial Additional Requirements • Sampling Frequency: minutes • Experiment Duration: years • Deployment Size: networks should be deployed in ways • that capture the heterogeneity of land use EmNets 2006 Life Under your Feet 5

System Architecture EmNets 2006 Life Under your Feet 6

Sensor Node Hardw are Sensors: • Watermark soil moisture • Irrometer soil thermistor • Onboard Temperature and Light • MicaZ motes • Waterproof cases, cables, connectors, ... • EmNets 2006 Life Under your Feet 7

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Mote Softw are Mote Base Mote Base status message data request data message 2min 1s Bulk Phase ... Send − and − Wait Phase ... Receiving Sending (a) (b) Sensors are sampled every minute • Raw measurements are stored in flash • Storage overrun in > 20 days • Data retrieved using NACK-based sliding window protocol • Each mote sends every 2 min a status messages to base- • station: (#meas, bat voltage) Web-accessible real-time monitoring • EmNets 2006 Life Under your Feet 10

Database Design DB Design derived from • experiment and WSN setup Self-documenting • framework Raw data follow a multi- • stage validation process Stored data available • through Web pages and Web Services Datacube for analysis • 7M datapoints collected • EmNets 2006 Life Under your Feet 11

Calibration w orkflow Calibrations Calibrations Mote Resistor Temperature Sensor Mote Resistor Temperature Sensor in the Lab Calibration Calibration in the Lab Calibration Calibration Temperature sensor Temperature sensor Voltage Voltage Soil Soil A/D units A/D units Resistance Resistance Temperature Temperature Reference voltage Reference voltage Voltage Voltage A/D units Moisture Sensor A/D units Moisture Sensor Calibration Calibration Moisture sensor Moisture sensor Voltage Voltage A/D units Resistance Water Deficit A/D units Resistance Water Deficit Soil Matrix Potential Soil Matrix Potential Light Intensity Light Intensity A/D units A/D units Temperature Temperature Air Temperature Soil Water Potential-> Air Temperature Soil Water Potential-> Conversion Conversion A/D units Volumetric Conversion A/D units Volumetric Conversion CPU clock CPU clock Air Temperature Water Content Air Temperature Water Content Celsius Volumetric Celsius Volumetric UTC DateTime UTC DateTime EmNets 2006 Life Under your Feet 12

Deploym ent Site 2m 2m 8m 10 motes deployed on a slanted grid, ~2m apart • 147 days of deployment • Basestation within direct radio range • Some links had unexpectedly poor quality • Had to collect some of the data using laptop • EmNets 2006 Life Under your Feet 13

Ecology Results ( Tem perature) EmNets 2006 Life Under your Feet 14

Ecology Results ( Soil Moisture) EmNets 2006 Life Under your Feet 15

Energy consum ption Motes go to sleep when • not collecting data/sending reports Easy to calculate • average current draw Powered by AA alkaline • batteries Linear discharge curve • Possible to predict node • lifetime EmNets 2006 Life Under your Feet 16

Data Transm ission Perform ance Good Link Lossy Link EmNets 2006 Life Under your Feet 17

Problem s w e encountered Waterproofing the boxes • Moisture sensor behavior in • the wild Power consumption • Data provenance • Reprogramming • EmNets 2006 Life Under your Feet 18

Conclusions Sensor Networks are still expensive in time, money and • know-how Need for data analysis tools • Need for increased confidence in collected • measurements End-to-End system that transform s raw • m easurem ents to scientifically significant data EmNets 2006 Life Under your Feet 19

Questions? For more information • http://www.lifeunderyourfeet.org/ EmNets 2006 Life Under your Feet 20