drifters design

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FSU/FAMU College of Engineering

Department of Electrical and Computer Engineering

Marine Drifters - Specifications and Requirements

Team 5

Team Members

Thomas SaulMichael Sprouse

Michael LintonSean Keenan

09/18/2012



EEL 4911C Senior Design I Fall 2012 Team #5Project: Marine Drifters Needs Analysis and Requirements Document

Authors: Thomas Saul, Michael Sprouse, Michael Linton, Sean Keenan

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1. Design Team OverviewThe primary team responsibilities are as listed and described but not limited to the following:

Team Leader – Thomas Saul – will maintain the overall organization and planning of the project and

make final decisions, and delegating additional project tasking when necessary. He will also ensure thatall assigned jobs and duties are progressing as expected and interfacing during the proposed timing

intervals. He will also have final review of all deliverables and presentations prior to submission.

Technical Responsibilities: Lead Engineer, Networking Design, Circuit Design, Programming

Business Administrator – Sean Keenan – is responsible for maintaining the flow of communication

between team members, the team advisor, and the sponsors. He is the first line of contact between the

sponsors, advisors, and team members in order to ensure the miscommunications do not occur. He takes

the lead in organizing, planning, and setting up all meetings, as well as maintaining an archive of all

correspondence, minutes, and deliverables. The business administrator is also responsible for drafting all

correspondence, deliverables, and presentations for the project with the assistance of the Team Secretary.

Technical Responsibilities: Power Analysis, Circuit Construction, Hull Design/Modification

Team Treasurer – Michael Sprouse – is responsible for managing the project budge and maintaining a

record of all debits and credits to the team account. He will also review all proposed purchases to ensure

every component either meets or exceeds the desired engineering capabilities as well as researching

viable component alternatives. Once the purchase request has been approved, he will then order the

desired quantity ensuring the budget is not exceeded. Additionally, he will prepare weekly budget reports

and present them to the team during regularly scheduled meetings.

Technical Responsibilities: Lead Programmer, Networking Design, Circuit Design/Construction

Team Secretary – Michael Linton – in charge of taking minutes during all team meetings andtranscribing/uploading the digital copies to the project webpage after each meeting. Also assists the

Business Administrator with drafting all correspondence, deliverables, and presentations for the team.

Technical Responsibilities: Power Analysis, Hull Design/Modification, Simulation

2. Needs Analysis

2.1 Overview of the Marine Drifters Project

Through the duration of this project, several variations have emerged with mixed results from both the

physical and electronic design aspects.

2.1.1 Generation 1 Drifter [1]

The goal for the Gen 1 drifter was to make a device capable of measuring water currents over the course

of several weeks (actual unit was only able to record for about 3 days on installed battery), recording GPS

fixes at least once an hour and transmitting them back to a shore base station for real-time monitoring and

recovery.





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Figure 2.1.1: Marine Drifter Gen 1

The following components were utilized in the Gen 1 drifter:

GPS receiver: Trimble, Lassen iQ (27mA current draw @ 3.3 V)

NMEA output (GGPA string)

Reacquisition time < 5 sec

External Antenna

Radio transceiver: Aerocomm, AC 4790-200 (50mA current draw @ 3.3 V)

100 mW output power

4 mile range (advertised)

Frequency hopping spread spectrum

902-928 MHz frequency band

76.8 Kbps data rate (baud rate)

External half-wave dipole antenna

Microprocessor: Parallax, BS2pe (15 mA current draw @ 5 V)

40 uA current draw in sleep mode

Programmable in BASIC

32 Kbyte memory

I/O lines for component control

Battery: AA Portable Power, 18650 (2000 mAhr each)

Li-Ion, rechargeable

Voltage Regulator Maxim, MAX883 (5 V regulated output)

200 mA output limit

2.1.2 Generation 2 Drifter [2]

The goal of the Gen 2 drifter was to redesign the Gen 1, maintaining the overall functionality wasparamount while increasing functionality and performance. For this model, temperature readings would

also be taken and transmitted with the GPS position data, and a complete hull redesign intended to reduce

the prevailing wind effect on the drifter while increasing the current drag coefficient and overall

performance in extremely shallow water. This drifter was also designed to store additional information

onboard which, when the drifter was recovered, could be analyzed and compiled with the real-time data

which had already been relayed to the shore.





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Figure 2.1.2: Marine Drifter Gen 2

The following components were utilized in the Gen 2 drifter:

GPS receiver: Fastrax UP501 (75mW power draw/25 mA current draw @ 3.0 V)

NMEA output (GGPA string)

UART Connection

10 Hz maximum fix rate

Reacquisition time < 5 sec

Internal Antenna

Radio transceiver: XBee-Pro XSC

100 mW output power

265 mA in transmit mode / 65 mA in receive mode / 45 uA in sleep mode (current draw)

6 mile range (advertised w/ 2.1 dB dipole antenna)

15 mile range (advertised w/ high gain antenna)

Frequency hopping spread spectrum

UART Connection

902-928 MHz frequency band

9600 bps data rate (baud rate)

External half-wave dipole antenna

Microprocessor: Texas Instruments M430G2553 (230 uA current draw @ 2.2 V)

Internal 32 kHz crystal oscillator

2 16 bit timers

Programmable in Assembly/C

12 Kbyte flash memory

512 byte Ram

1 UART Connection

I/O lines for component control

Memory Card Module: Sparkfun BOB-11403

SD Card or MicroSD with Converter

Serial Port Module: Pololu 23201a





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250 kbps maximum data rate

Temperature Sensor: Maxim DS18B20

Temp Range -55C to +125C

Accurate to 0.5C

Converts temp to 12-Bit word in 750 msec (Max) Unique code for each sensor

Battery: ULTRAFIRE 18650 (3000 mAhr each)

Li-Ion, rechargeable

Voltage Regulator Maxim, MAX883 (5 V regulated output)

200 mA output limit

2.2 Statement of the Problem

The complexity of this project lies in the proper selection of 5 main COTS components which must

interface with each other seamlessly. In previous versions, interfacing issues have plagued the project

with problems therefore limiting its overall success. Therefore the selection of these components will bebased not only on power requirements and efficiency, but also required communication protocols and

languages, and the ease of use and implementation. The main idea for this project is to construct a mid-

range, self contained, shallow water drifter network capable of data replication and data forwarding to

ensure data survival regardless of drifter retrieval. With the possibility of recovery failure, therefore the

components selected will also be chosen based on monetary considerations too.

Required Capabilities:

CAP-01: The device must be battery powered.

CAP-02: The device must be inexpensive, compact and lightweight.

CAP-03: The device must be able to record temperature and positional data.

CAP-04: The device must be able to communicate and transmit its data to the shore.CAP-05: The device must be able to communicate with other units and share/backup data.

CAP-06: The device should be impact resistant.

CAP-07: The device must be waterproof.

Desirable Capabilities (in order of highest to lowest priority):

CAP-08: The devices must be easily configurable, deployable, and replicable.

CAP-09: The device should sit as low in water as possible to maximize current drag while minimizing

wind effect.

CAP-10: The device should be able to be recovered in sequential order based on unit specifications to

ensure drifters do not float out of range during retrieval.

CAP-11: The device should be hard to see while deployed yet not impossible to find during recovery.

CAP-12: The device should emit an audible proximity alert and or a visual signal when in recovery

mode.

2.3 Operational Description

The user will take the drifters to the Ochlocknee Bay, switch them on, and put the drifters into the water

as a hive. At this point, the drifters will be tracked as they drift with the current in the bay, recording their





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data as they float and relaying this data to the shore. Each drifter will also communicate with any

neighboring drifter within range (determined by LOS and atmospheric constraints), transferring its data to

the subsequent drifters. Heavy rain and wind may have adverse effects on the data relay system which

should be corrected when the weather clears by retransmission of any data which has not already been

successfully received, providing the drifter(s) affected by the adverse condition have not floated out of range of another drifter in the network. When the base station is turned on, the drifters within range will

then transmit their data to the base station in turns, with only the data which has not already been recorded

by the base station for the individual drifter being updated. Thus if all units are within range, a

connection with only one drifter would be required to retrieve all of the position and temperature data for

the entire network. If the unit encounters a shoal or sandbar during a low tide condition, the unit should

remain upright and continue to communicate with the neighboring drifters until the water level returns to

a height to which the drifter will float again. When measurements are complete, the drifters will be

recovered based on approximate locations from the last GPS fix from the individual unit and ongoing

wireless communication with each unit and the portable base station.

2.3.1 System Inputs, Outputs and Interfaces Inputs

o Temperature: this input will be received by from the built in temperature sensor

o GPS Data: this input will be received from the GPS receiver

o Radio Frequency: will be used for location and retrieval of the drifters from the base

station as well as receiving data streams from neighboring drifters.

Outputs

o SD Card memory: this output will be used to store the data received from the inputs to

the system.

o Radio Frequency: this wireless output will be used as a mode of data transfer while the

drifter is deployed and information transfer while the drifter is in retrieval mode.o Serial port: this output will be used on the base station for real-time monitoring of the

drifter network and periodic network data retrieval.

Interfaces

o Serial-USB: this interface will be used to allow a computer to periodically download the

drifter network data by syncing with the network. This will also allow the user to

monitor the network in real-time to ensure units are operating as expected (i.e. units have

not been picked up by a passerby) and what units are still within range of the base station.

2.3.2 Environmental and Safety Considerations

The drifter units are designed to operate in a temperate climate with air and water temperatures

ranging between 0 – 50 degrees Celsius (or 32 – 122 degrees Fahrenheit). Any temperaturesoutside of the stated ranges could possibly result in shortened batter life, battery explosion, or

damage to other electronic components.

Due to the possibility for condensation inside the electronics storage module of the drifter during

a wide range of temperature changes, a desiccant pack will be installed to ensure the storage

module remains dry and the electronics remain unaffected by excess moisture.





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Due to the probable use of a “Lithium” family battery module, the need for waterproof integrity is

paramount to ensure the modules are not exposed to any undo moisture which could result in

possible fire or explosion. The installed desiccant pack will also help reduce the chance of this

occurring.

3. Requirements SpecificationsThe following requirements lists the technical specifications required by the sponsor and define the

internal workings, technical details, processing, and functionality necessary for proper operation of the

drifter network.

3.1 Functional Requirements

The following requirements are either directly impacted by the operation of the unit or required for proper

operation of the drifter network

REQF-01: The battery lifetime should be no less than 15 days to allow for longer deployment times.REQF-02: The drifter should record position and temperature data approximately every 3 minutes or

approximately 6000 fixes over the 15 day duration.

REQF-03: Each drifter must have a minimum transmission range of 5 km to allow for the drifters to

remain in contact with each other over greater distances thus increasing the overall accuracy

of the network.

REQF-04: Each drifter must have sufficient storage capacity (~1-2GB) to store data from itself and at

least 20 additional networked drifters.

REQF-05: Each drifter must have a maximum weight of 2 kg in order to reduce the draft of each drifter

while supplying sufficient space for the electronics module within the hull, and increasing the

accuracy and reliability in shallower waters.

REQF-06: Each drifter must have a maximum height of 10 cm (20 cm with antenna) in order to float

over obstructions in shallow waters.

REQF-07: The drifters must be waterproof up to a depth of 5 meters to ensure that electronic components

remain safe from water damage at all times.

REQF-08: The drifters must be able to withstand a 2.5 N (0.6 Lb) force applied by a spherical surface

with a 5 mm radius in order to ensure the drifter's survival after impacting boats, oyster beds,

or other floating obstacles.

REQF-09: The drifters must be able to float in waters with a minimum depth of 0.25 meters to ensure it

does not run aground during extended periods of time afloat.

REQF-10: The drifters must be able to transfer data to neighboring drifters via radio wave transmission

without data loss or interference as a means of data collection backup.

3.2 Non-functional Requirements

The following requirements do not directly affect either the operation of the drifter or the drifter network.

REQN-01: The radio frequency used for data transfer between drifters should be an open frequency that

does not require FCC licensing [3].





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4. Preliminary Test PlanThe following plan comprise the proposed and tentative component and system tests to ensure overall

electronic functionality as well as finalized drifter and network design tests.

4.1 Capabilities Test PlanCAPT-01: Test the power up and operation of individual components prior to their use in the proposed

drifter electronics module design.

Req. Tested: CAP-01, CAP-03, CAP-04, CAP-05

Materials Needed: All electronic components intended for use in the drifter electronics

module design, computer, multimeter, oscilloscope, stop watch, voltage

source.

Location: COE (senior design lab)

Testers: Any Team Member

Steps:

1. Each component will be attached to the voltage source, oscilloscope, and multimeter

to verify the component powers on.

2. Once the component is verified to accept the appropriate input voltage (~3.0-5.0 V),

the response of the component will be monitored with the oscilloscope and

multimeter through the computer LabView software to ensure the component

responds as expected (primarily used for microcontroller and memory reader).

3. The temperature sensor will be tested connected once again to the computer,

mulitmeter, and oscilloscope to determine if it accurately measures the temperature

of the lab (further tests will occur as development continues). This test will ensure

the device is not defective.

4. The GPS receiver will be connected to the computer, multimeter, and oscilloscope to

determine if once activated, the data pin indeed pulses information as stipulated inthe design specs (further tests of the GPS will occur as development continues).

5. The radio transceiver will be connected to the computer via the serial interface,

activated, and tested to ensure proper communication occurs when the component is

properly triggered (further tests will occur as development occurs).

CAPT-02: Determine and record the mass of each component for later analysis and constraints planning.

Req. Tested: CAP-02

Materials Needed: All electronic components intended for use in the drifter electronics

module design, proposed hull, triple beam balance (or digital scale).



Steps:

1. Each component type will massed (using the triple beam balance or digital scale) as a

group (i.e. all GPS modules at once), once the mass has been determined the average

component mass will be recorded.





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Testers: 1 Team Member (some unattended time)

Steps:

1. The system electronics module will be attached to the multimeter, oscilloscope,

computer, and the battery pack. Once all connections are made, the two modules willbe switched on.

2. The two units will be monitored for the full 15 day period to ensure the battery life is

sufficient to last the duration (note, the second unit is only used to simulate data

transfer rates to get a true reading of transceiver current draw during transmission.

3. When the test is complete, the battery pack voltage and current will be measured to

determine the overall system efficiency. If the batter is dead prior to the end of the 15

days, the test will cease and the failure will be reassessed. Once corrected the test will

be repeated from the beginning.

4. Once a successful test is complete, the data cards from one of the two modules will

be pulled and the number of data fixes will be checked to ensure that there are at least

6000 GPS fixes and temperature readings thereby successfully completing this test.

REQT-02: After successful completion of electronics module system test, the two units will be taken to a

clear area for a total range test.

Req. Tested: REQF-03

Materials Needed: 2 fully assembled system electronics modules, 2 battery packs, computer,

and 2 cell phones.

Location: Open location (possibly beach)

Testers: 2-3 Team Members

Steps:

1. One electronics module will be attached to computer, and the battery pack andswitched on and placed on the ground and one team member will monitor the

computer for the duration of the test. Cell phones will be used by the team members

to communicate instructions to the moving drifter team.

2. The second module will be switched on, and communication between the drifter and

the base station will be verified. Once the data is flowing, the drifter will be walked

in intervals of approximately 0.5 km and the data stream will be re-verified. This

process will be repeated until the data stream stops.

3. Once the data has stopped, the drifter will be brought closer until the data stream is

reinitiated. This will be marked as the maximum length and the distance will be

determined by the GPS locations recorded at the last good position.

4. If this range is less than the desired 5 km then the output power of the drifter will be

increased and steps 2-4 will be repeated and re-verified. If this is greater than the 5

km desired distance the new power output settings will be figured into the total and

REQT-01 will be repeated to ensure the 15 day lifetime is still valid.

5. Once the desired range is realized, this test will be repeated in medium and heavy

rain conditions to test the range reduction due to adverse weather conditions. These

ranges will be recorded as limitations to the overall system performance.





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REQT-03: Test storage system capacity for network of 5 drifters to ensure sufficient space during 15 day

drifter lifespan.

Req. Tested: REQF-04, REQF-10

Materials Needed: 5 fully assembled system electronics modules, 5 battery packs andcomputer.



Steps:

1. After the successful completion of REQT-01 and REQT-02, the five electronics

modules will be connected to the battery packs and switched on.

2. The five units will be monitored for the full 15 day period to ensure the battery life is

sufficient to last the lifespan duration.

3. When the test is complete, the battery pack voltages and currents will be measured to

determine the overall system efficiency. If any of the batteries are found dead prior to

the end of the 15 days, the test will cease and the failure will be reassessed. Once

corrected the test will be repeated from the beginning.

4. Once a successful test is complete, the data cards from one of the five modules will

be pulled and the number of data fixes will be checked to ensure that there are at least

6000 GPS fixes and temperature readings per drifter with a complete set of fixes

from each of the other four drifters as well, and that there is sufficient space to store

at least 25 more data sets from additional possible drifters.

5. Additionally, the data sets will be analyzed to ensure that the information transferred

from the other drifters isn’t duplicated. This will be considered a successful test of

the data transfer flow path.

REQT-04: Measure and record the total weight of the fully assembled drifter.


Materials Needed: 1 fully assembled drifter, triple beam balance (or digital scale).


Testers: 1 Team Member

Steps:

1. The fully assembled drifter assembly will be massed and recorded.

2. This mass will then be compared to the summation of component masses obtained in

test CAPT-02. If the two masses are with the tolerance of 50 grams and the overall

mass is less than 2 kg the test will be considered successful.

3. If the test is unsuccessful, component construction will be reevaluated to determine

whether or not additional mass can be removed without affecting drifter operational

characteristics.

REQT-05: Measure and record overall height of fully assembled drifter.


Materials Needed: 1 fully assembled drifter, pencil, laser level.





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Testers: 2 Team Members

Steps:

1. The fully assembled drifter will be placed on a flat surface by a team member. Then

the laser level will be positioned at the top of the antenna and the beam will intersectthe wall.

2. A mark will be drawn on the wall corresponding to the height to the top of the

drifter’s antenna, then the height of the table will be subtracted, thus yielding the

overall height of the fully assembled drifter. Additionally, the length of the antenna

is known therefore the drifter hull height is known as well. Both of these will be

recorded.

3. If the hull height is less than or equal to 10 cm and overall height with antenna

attached is less than 20 cm the test will be considered successful. If not the drifter

design will need to be reevaluated in an attempt to reduce the overall height to within

the constraints listed in REQF-06.

REQT-06: Test assembled drifter hull, less the electronics module, to ensure the design is waterproof to a

depth of 5 meters.


Materials Needed: 1 fully assembled drifter hull including antenna, 15 lb weight, 6 meters

of string.



Steps:

1. This test will be completed in accordance with CAPT-04 to a depth of 5 meters for a

period not less than 3 hours.2. The small timeline is due to the fact the drifter is not designed to be completely

submerged for extended periods of time therefore, water resistance for a period of 3

hours should prove sufficient.

3. After the completion of the test, the drifter will be inspected for signs of leakage and

moisture inside the electronics bay. If the bay is dry and moisture free, the test will

be considered successful.

REQT-07: Determine the impact resilience of the drifter hull material.


Materials Needed: Drifter hull material sample, impact tester, spherical impact end (5mm

radius)

Location: COE (smash lab)


Steps:

1. This test will be conducted in accordance with CAPT-03 to a required force of 2.5 N

(~0.60 lbf).





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2. The 2.5 N force will be applied to the sample by the impact tester with the spherical

impact end with radius of 5 mm, at which point the sample will be inspected for signs

of deformation, fracture, and indentations.

3. Continue with proceeding steps from CAPT-03 until the test is complete.

REQT-08: Measure the maximum draft of a fully assembled drifter to ensure it can float in a minimum of

0.25 meter water depth.


Materials Needed: 1 fully assembled drifter.

Location: Small pool or bathtub with 0.25 meters of water depth


Steps:

1. Fill the small pool or tub with not more than 0.25 meters of water.

2. Place the drifter in the water and verify that it floats without the bottom of the drifter

touching the bottom of the pool/tub.

3. Failure of the drifter to touch the bottom will signify a successful completion of the

draft test.

4.3 Constraints Test Plan

CONT-01: The total cost for the fabrication of 5 drifters cannot exceed $1000.

Req. Tested: CONS-01

Materials Needed: Invoices for all components ordered and utilized in the finalized drifter

design.

Location: COE


Steps:1. The invoices will be reviewed and the cost for each drifter component will be

averaged including shipping costs.

2. These costs will then be added together and verified to be less than $1000.

3. If the costs are more than $1000, the test will have failed this constraint and alternate

suppliers will need to be sourced or the design will need to be altered to

accommodate for a lower cost.

4. This test will be repeated until passed.

CONT-02: Drifters must be completely reproducible without the need for outsourcing any of the

fabrication.

Req. Tested: CONS-02, CONS-03

Materials Needed: All design documents, full list of all equipment required for assembly

and configuration of the drifter units, review of any testing equipment

necessary for completing drifter assembly.

Location: COE


Steps:





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1. All electronics will be sourced and cost analysis for fabrication will be attained by

drifter design team. This will allow components to be ordered from fabrication

center thus reducing the technical knowledge required for final drifter assembly.

2. The hull structure will be sourced and cost analysis for fabrication will be attained by

drifter design team. This will allow for the hull to be ordered and fabricated by asupplier thus reducing the mechanical and materials training and knowledge required

for final drifter assembly.

3. Drifter designs and procurement options will be presented to the FSU Oceanography

Department for review.

4. Design will be re-evaluated if deemed so by the marine lab due to complexity of

proposed design. If the proposed design is accepted by the marine lab, the test will be

deemed successful

5. This test will be repeated until deemed successful.

CONT-03: All hull engineering designs will be created using SolidWorks or Pro-Engineer Wildfire


Materials Needed: N/A

Location: COE


Steps:

1. All engineering designs for the hull assembly will be created using either SolidWorks

or Pro-Engineer Wildfire. These programs are chosen based on the industry standard

for hull fabrication facilities that will be used.

2. For ease of review, all engineering designs will be saved in PDF format so they can

be opened on any computing platform.

3. All documents will be verified to open on all common computer platforms, this willsignify the successful completion of this test.

CONT-04: All electronic circuit diagrams must be created using industry standard software.


Materials Needed: N/A

Location: COE


Steps:

1. All circuit diagrams for the electronics module will be created using software which

is accepted by industry fabrication facilities. These will be chosen at a later date after

the fabrication facility has been chosen.

2. For ease of review, all circuit diagrams will be saved in PDF format so they can be

opened on any computing platform for review and turnover to FSU Marine Lab.

3. All documents will be verified to open on all common computer platforms, this will

signify the successful completion of this test.





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5. List of DeliverablesThe following list of items constitutes the proposed project deliverables which will be turned over to the

Marine Lab at the completion of this project. This list is by no means all inclusive and is subject to

change through the duration of this project as needs arise.

Comprehensive User’s Manual

1 fully assembled and configured base station

o 1 – Otter box

o 1 – Communication electrons module

o 1 – Serial interface

o 1 – 2.1 dB dipole antenna

o 1 – Antenna connector

o 1 – Secure Digital data card

o 1 – Battery pack

o 2 – USB to serial interface cable

5 fully assembled drifters

o 5 – Drifter Hulls

o 5 – Communication electronics modules

o 5 – 2.1 dB dipole antennas

o 5 – Antenna connectors

o 5 – Secure Digital data cards

o 5 – Battery packs

Electronics module circuit schematics.

Hull engineering designs.

All code files for configuration of microcontrollers.

2 development boards for configuration.

6. References[1] Fall 2011 senior design group number 7, “Fall 2011 Needs Analysis and Requirements,” unpublished

[2] Fall 2011 senior design group number 7, “A Self Contained Network of Shallow Water Drifters,”

unpublished

[3] Digi International Inc, “FCC Equipment Authorization,” 2/28/2008, unpublished

URL: http://www.digi.com/pdf/agencyapprovals/FCCGrantXBee-PROXSC.pdf

[4] W.E. Schmidt, B.T. Woodward, K.S. Millikan, and R.T. Guza, “A GPS-Tracked Surf Zone Drifter”,

July 2003, American Meteorological Society

End of Document

http://www.digi.com/pdf/agencyapprovals/FCCGrantXBee-PROXSC.pdf




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