1. Megan Wolfe Investigating Tidal Currents using GPS Shallow-water Drifters in Grappler Inlet Megan Wolfe

2. Table of Contents The Question The Question Revised Design and makings of the drifters Problems encountered Analysis and Discussion up to Date

3. The Question Team B’s layer of Ice Very thin layer of fresh water distributed throughout Grappler Inlet Wanted to determine how the tidal currents effected the distribution of the fresh water layer in Grappler Inlet

4. Revising the Question Problem! Thin fresh water layer was too thin!! - Fresh layer was only 3-10cm Could not design a drifter that would rest in the top 3-10cm which would not be influenced by the wind. Investigating the tidal currents throughout Grappler Inlet at 3 different depths: Surface, 1m, and 2m.

5. Design of the Drifters Three Drifters built using everyday materials -Duct Tape -Styrofoam -plastic bags -rocks: used to balance drogue New and improved tracking: GPS units 2m 1m Surface Two parts of a Drifter -The drifter -And the drogue

6. Surface 2m 1m

7. Experimental Problems Bulky design of drifters Shore encounters Low tide -shallow waters -change in tide during experiment

8. Analysis and Discussion A look at all three of the drifter paths CTD temperature and salinity readings Separate out and focus on individual drifters paths GPS accuracy

9. Big map Longitude E Latitude N Grappler Inlet with Drifter Destination -125.13-125.125-125.12-125.115-125.11 48.829 48.83 48.831 48.832 48.833 48.834 48.835 48.836 1m Drifter Surface Drifter 2m Drifter Colored Dots Represents areas where CTD readings were taken

10. CTD Temperature and Salinity Temperature at surface is cooler due to fresh water layer/ice layer, peaks around 1m and decreases with depth Comparing Salinity and Temperature, Salinity seems to increase with depth, opposite to what the temperature is doing

11. Surface Comments During outgoing tide, not much movement: Ice hindrance Incoming tide: Lots of movement, traveled farthest, but wind present 050100150 -150 -100 -50 0 50 100 150 200 250 300 Time (min) Distance traveled Latitudinally (meters) Surface Drifter Latitudinal Distance Traveled over Time

12. 1m Drifter 050100150 -400 -300 -200 -100 0 100 200 Time Traveled (mins) Distance Traveled Latitudinally (meters) Distance Traveled Latitudinally by 1m Drifter vrs. Time Zoomed in on White Box Zoomed in on Black Box: Standard Deviation = 1.347m

13. 2m Drifter 2m 020406080100120140160 -150 -100 -50 0 50 100 150 Distance Traveled Latitudinally (meters ) Time Traveled (mins) Distance Traveled Latitudinally by 2m Drifter vrs. Time Zoomed in white box Zoomed in Black box: Standard Deviation = 2.6832m

14. GPS Error Six classes of GPS Error -Ephemeris data: Transmitted location errors of the satellite -Satellite clock: Errors in the transmitted clock, -Ionoshpere: Errors due to the corrections of pseudorange caused by ionospheric effects -Troposphere: Errors due to the corrections of pseudorange caused by tropospheric effects -Multipath: Errors caused by reflected signals entering receiver antenna -Receiver: Errors in the receiver’s measurements of range caused by thermal noise, software accuracy, and inter-channel biases

15. Comparing GPS Accuracy Determining GPS accuracy 2m drifter: low tide coming to the rescue Comparison with other GPS accuracy tests Compact, low-cost GPS near shore drifter: Center for Water Research, U. of Western Australia Power Spectra of the residuals: Difference between the recorded position from the mean time- averaged position. The standard deviation of the position from the mean was 1.3m in Easting direction and 1.6m in the Northing direction

16. Determining GPS Accuracy 2m Drifter ran a ground: became stationary for 40mins. A good estimation of GPS accuracy Standard Deviation = 1.8864m

17. Design of a smaller, compact GPS drifter that contains ‘off the shelf’ components Costs:$350 plus an estimated 8hrs of preparation Drifter Improvements Effects due to wind stress - Less surface area exposed Lack of materials and resources Design of a smaller, compact GPS drifter that contains ‘off the shelf’ components

18. References A Compact, Low-Cost GPS Drifter for Use in the Oceanic Nearshore Zone, Lakes, and Estuaries,Journal of atmospheric and oceanic technology [0739-0572] Johnson yr: 2003 vol: 20 iss: 12 pg: 1880 A GPS-Tracked Surf Zone Drifter,Journal of atmospheric and oceanic technology [0739-0572] Schmidt yr: 2003 vol: 20 iss: 7 pg: 1069