Geolocation using light levels Niklas Wahlström 1 Fredrik Gustafsson 1 Susanne Åkesson 2 1 Division of Automatic Control Linköping University 2 Centre for Animal Movement Research Department of Biology Lund University
Mr Swift Common swift, Apus apus. Weight: 40 g Equipped with light logger (light sensor, battery, memory, clock). Weight: 2g Released on Aug. 5, 2010, found 298 days later We want to track Mr Swift!
Light levels State of the art: Compute time for sunrise and sunset For each time instance convert to Midday (gives longitude) Day length (gives latitude)
Light levels Nonlinear filtering solution Measurement update at each sunrise and sunset Motion model with two modes (stationary and migration mode). Solve with a marginalized particle filter.
Contribution Light levels localizing animals has been used since the 80 s Nonlinear statistical filtering has also been used for a while. Not much has been done combining the two. Contribution: Using light levels in a statistical filtering framework.
Light intensity data Sampling time: 10 minutes. Resolution: 6 bits (2 6 = 64 values) Saturated for both low and high values. Light intensity 60 40 20 Measurement Threshold Sunrise Sunset 0 0 1 2 3 4 5 6 7 Time [Days]
Light intensity data Some problems Light intensity The event will shift several minutes depending on the threshold. Will also depend on weather conditions and geographic environment. 60 40 20 Sunset 0 21:53 22:13 22:33 22:53 23:13 Time
Light intensity data More problems If the bird is hidden during sunrise and/or sunset, it might cause missing data. Light intensity 60 40 20 Missing data Measurement Threshold Sunrise Sunset 0 0 1 2 3 4 5 6 7 8 Time [Days]
Sunrise and sunset 24 21 18 Time [h] 15 12 9 Sunrise Sunset 6 3 0 08/05 09/23 Sep. Equinox 12/21 Dec. Solstice 03/20 Mar. Equinox 05/29
The data Sunrise and sunset events This work Light intensity data Trajectory
The data Sunrise and sunset events This work Light intensity data Trajectory Future work
The likelihood - May 6 Daylight map, 06 May 2011 06:00:00 Likelihood, sunrise, 06 May 2011 06:00:00 Likelihood, sunset, 06 May 2011 18:00:00
The likelihood - Summer solstice Daylight map, 21 Jun 2011 06:00:00 Likelihood, sunrise, 21 Jun 2011 06:00:00 Likelihood, sunset, 21 Jun 2011 18:00:00
The likelihood - Autumn equinox Daylight map, 21 Sep 2011 06:00:00 Likelihood, sunrise, 21 Sep 2011 06:00:00 Likelihood, sunset, 21 Sep 2011 18:00:00
Prior
Measurement update - sunrise. Time: 05-Aug-2010 03:04:00
Time update. Time: 05-Aug-2010 19:10:59
Measurement update - sunset. Time: 05-Aug-2010 19:11:00
Time update. Time: 06-Aug-2010 03:08:59
Measurement update - sunrise. Time: 06-Aug-2010 03:09:00
Time update. Time: 06-Aug-2010 18:46:59
Measurement update - sunset. Time: 06-Aug-2010 18:47:00
Time update. Time: 07-Aug-2010 03:38:59
Animation
The Voyage Trajectory 60 N 05/29 08/05 09/03 05/27 30 N 11/01 0 10/03 30 W 0 30 03/29 12/01 02/27 E 01/29 12/30 04/27
The Voyage 60 N Sunrise Sunset Start and end position 05/29 08/05 09/03 05/27 30 N 11/01 0 10/03 30 W 0 30 03/29 12/01 02/27 E 01/29 12/30 04/27
The Voyage 60 N Sunrise Sunset Start and end position 05/29 08/05 09/03 05/27 30 N 11/01 0 10/03 30 W 0 30 03/29 12/01 02/27 E 01/29 12/30 04/27
The estimated mode 1 0: Stationary mode, 1: Migration mode 0 08/05 09/23 Sep. Equinox 12/21 Dec. Solstice 03/20 Mar. Equinox 05/29
Comparison Latitude 50 Our solution Existing solution Degree [ ] 0 50 09/03 09/13 09/23 10/03
Summary and future work Summary Tracking using light levels Measurement update at each sunrise and sunset Applied on real world data Future work Do smoothing Process light intensity data, handle missing data, false alarms etc. Validate on data with ground truth (GPS mounted on heavier birds)