Northeast Fisheries Science Center
Drifters: Design, Construction, Use...
(last modified June 2010)
History of our drifter production
- Student involvement
- Redundant development
- Oceanographic standards/configurations
- Contributions to IOOS with common data delivery and archive
2004, we were funded by NOAA's Northeast Consortium to develop
student-built, satellite-tracked, lobstermen-deployed drifters. This
was the fourth phase of the Environmental Monitors on Lobster Traps
project (see Manning and Pelletier, 2009 and emolt.org).
Funded parties including the Gulf of Maine Lobster Foundation,
the Southern Maine Community College (SMCC), and NOAA's Northeast
Fisheries Science Center were interested in tracking the potential
transport of early-staged larvae along the coast of Maine. In
subsequent years, we were primarily funded by McGillicuddy et al in
another NOAA funded project (GOMTOX) to track the advection of HABs
(Manning et al, 2009). Another
big boost to the project occurred in the summer of August 2009 when we
hosted a NSF-funded workshop to teach a few dozen educators from around
the country (from the Marine Advanced Technology Education (MATE)
consortium). Several other investigations are documented elsewhere. Applications funded to date include:
of the primary motivations for drifter deployments is to help validate
the many numerical circulation models as well as the growing network of
- Lobster larvae advection
- Harmful Algal Bloom advection
- Zooplankton (whale food) advection
- Educational demonstrations
- Invasive crab dispersal
- Transient eddy formations
- Fish larvae (salmon,cod) advection
- Power plant effluent dispersal
- Clam acidification
Given multiple years with multiple fundings, the dataset to conduct such statistics is rapidly growing.
eMOLT "Rachel" Drifter vs Davis "CODE"
Most surface drifters in use today are the "Davis CODE" design
first described decades ago by Davis (1985) for the Coastal
There are specifications and pictures of this type of drifter in each
the manufacturer's web sites below (Table 1). However, since they
are often fitted with costly (~$2K) GPS electronics, we found, in
our case of very limited budget, it was unwise to
use them along the coast of New England due to the high
of running aground and being picked up by curious lobstermen and
Table 1. Some existing surface drifters that have performed
well over the last decade or two
Having eliminated the costly electronics within the housing unit, we
simply mount a relatively inexpensive GPS transmitter (similar to those
used by the trucking industry on the highway) on a smaller
(~2 inch) diameter foam-filled PVC pipe (ballasted appropriately).
Since it is built by
at the Southern Maine Community College and originally funded by the
Monitors on Lobster Trap project, we call it the eMOLT SMCC
"Rachel" Model (drifter models are named after the new students
spent the most time on design and construction). From our
in using hundreds of these drifters since 2004, we can reduce the cost GPS drifters 3 times. While these
homemade rigs typically survive several months, they do not
survive nearly as long as the commercial products noted above. Nevertheless, they
have so far logged hundreds of thousands of kilometers of ocean. While they are
designed to be expendable for the most part, with some effort and ship
time, of course, they are reusable. Batteries are
good for several months with near-hourly samples. See more on "survival statistics" below.
How the system works and who is involved
There are six institutions/companies currently involved:
Interested scientist and educators communicate with:
- "Gulf of Maine Lobster Foundation" (GoMLF) non-profit processes orders
- "AXXON" manufacturers the GPS transmitters
- "Southern Maine Community College Marince Science Department"
build the units
- "CommTech Mobile DataCom" is the satellite service provider (like ARGOS)
- "Globalstar", the folks that float the low-orbitting satellite
- "NOAA" promotes the use of these drifters and processes the data
It is best to copy all three parties in your email communications.
- Erin at GoMLF
(207-985-8088, firstname.lastname@example.org) to process orders
- Jim at NOAA (508-495-2211, email@example.com) to discuss hardware/software issues
- Tom at SMCC (207-741-5641, firstname.lastname@example.org) for details on custom hardware modifications
Assembling Standard "Rachel" drifter
This requires about 15 minutes per unit. A flathead screw driver & pliers needed.
Note: An older version of these instructions is posted here with pictures
but that needs to be updated.
- insert the four fiberglass into holes of the mast w/longer 55" rods on top
- hose clamp the rods so they remain symetrically in place
Note: socket wrench works best here but flat head screw driver will work
- slip on the four sails (~19" by 36")
- put 4 cotter pins on the outside end of sails at top
- slip on 4 stainless washers
- slip on 4 floats
- repeat 5 and then 4 to secure the floats
- hose clamp transmitter in place on top if not already
Putting units to sleep
- Programming units on a PC
- download the latest software
version 2.7.003 (if not already)
- unzip software
- execute the installation program
- Installs USB driver
- Install tracker software
- Connect wireless dongle to USB port
- Click on tracker software (software steps depends on tracker model)
- TrackPacks (2010), for example, use "TrackPack Configurator" java as follows:
- Enter passkey ad5d5kmsi48plc
- Click on "Search for units"
- highlight unit of interest
- select configuration/sample rate desired (typically 24/day samples)
- Click on "configure" on the bottom right panel
- make sure you get a check mark next to id number or try again
- place the transmitter right-side-up in a sky-view position
- Troubleshooting programming problems
- Does the program window popup? If not, does your Windows machine have Java 1.6 JRE or greater?
- Does it say "Connecting to Comm Port X" in lower left? If not:
- try alternative Commport via "Options" tab
- did you install the dongle driver by executing the driver installation program?
- If so, you may need to click on the driver installation icon
and "repair" the driver.
- Does the dongle have a green light illuminated? If not, try a different dongle
- Does the scan not locate a transmitter? If not:
- make sure your laptop is powered sufficiently (ie plug it in)
- make sure the transmitter is located nearby
- try clicking "scan for new unit" if this transmitter hasn't been used before
- connect to particular unit as in steps above
- click on "inventory"
- click on "configure"
- make sure you see a "1 successful" notice in the lower tleft
- make sure you get a green check mark next to the ESN number at top of the screen
- put the unit in sky view for awhile to double check the fact that it is really asleep (ie in "inventory" mode)
Documenting deployments and recoveries
In an attempt to automate the operation, users are asked to enter their deployment and recovery information on a web based forms.
the complete system is not operational at the time of this writing (Sep
2009), the plan is to serve data and googlemap plots without further
Tracking Units on the Web
- Option #1: best for getting details of most recent fixes
- log on to http://www.comtechmobile.com
- username: <call Jim Manning 508-566-4080>
- password: <call Jim Manning 508-566-4080>
- click on "Select Mulitple Units" (if needed)
- select unit IDs of interest (pe 0-18766)
- select "messages" to see mapquest-like map of positions
- zoom in and out, click other views, etc.
- Option #2: best for a quick summary of recent deployments
- Option #3: Alternatively, you can have the data:
- automatically emailed directly to you
- sent to your ftp site
- or you can query it when you want.
- Option #4: best for summary of all drifters to date
Other Drifter Configurations
These units, prototyped during
the winter of 2004 and 2005,
are designed to track a subsurface layer. There are three
components to the unit:
- The drogue is constructed stiff fiberglass hoop
rings that supports sheets of heavy-duty vinyl cloth
material. The length of the drogue will be adjustable to 1.5
meter lengths. The cloth is glued securely to hoops
w/additional strips of cloth in a manner such that the stress is
tangential (not normal) to the seam. The bottom-most hoop is weighted
slightly and additional buyancy is added to the upper-most hoop to
provide a more vertical profile in the water. The cloth has two
30cm-diameter holes cut out in each 1.5m section placed 180 degrees.
- The tether is typically a narrow (1/8t") statinless
wire connected to a 3-point
bridle on the topmost hoop with a stainless ring
(either circular or pear shaped) and a swivelling shackle (1/2" of
more). Heavy duty stainless wire used for the bridle
will be well protected from chaffing particularly at the ring
connection. The upper end of the tether is connected to the underside
of the surface configuration. Tether lengths
will be adjustable depending on the project and
terminated with thimbles and sleeves.
- The surface
configuration of these units has been either:
- 2-3'-length of 4" PVC pipe
that simply acts as a platform for the satellite transmitter riding above a 2-3'
length of 2" PVC pipe OR
- a Norwegian float that absorbs the drogue pull with a separate
unit tether behind that houses the transmitter. It is usually configured
similar to the "rachel" design described above (without the sails). The length of this surface
tether is adjustable.
The design is follows the specifications of
the World Ocean Circulation Experiment to insure that the units
have acceptable drag ratios of more than 40:1 and that slippage is
minimized. These units were tested in the spring of 2005. A set of them were
deployed in the Bay of Fundy in May 2005 and June 2006 and mid-coast Maine in July
2005 (Aretxabaleta et al, 2009).
w/telemetered temperature sensors
We have added
additional features to
the basic design.
- A temperature sensor similar to those used by refrigerator trucks
on the highway have been be incorporated by interfacing it with the
AXTracker. We tested this feature with at least one unit in April
- Tension sensors are often included on drogued drifters to
indicate the presence or absence of the drogue. Alternatively, we may
consider including a temperature sensors immediately above and below
the water line such that, given the drogue tension loss, should record
detectable variations in air temperature.
- Internally recording temperature probes can be easily installed
at multiple depths to monitor the thermal stratification.
- To aid in visibility, orange surface flotation can be easily
tethered to the surface configuration and strobe lights can be secure
to the PVC housing.
"Paul" drifter w/reinforced construction for inshore work
student, Paul Hodder designed this more-rugged design for
inshore/estaurine work during
the 2005-2006 school year. Dozens of deployments have been made since.
"Kathleen" bucket drifter for very-near surface work
model was originally designed for UMASS's Dan McDonald to look at the
top 30cm of the Merrimack River Plume in the Fall of 2009.
simply an inverted plastic bucket that is properly ballast to float
just below the surface. The transmitter is mounted a few inches above
"Super buckets" were also deployed with strobe lights (>4 mile visibility) and internally recording:
- temperature (multiple depths)
- salinity (StarOddi DST-CT)
- more frequent positions (Garmin units)
This drifter was designed to eliminate flotation at the ends of the
sail spars. It uses instead the natural buoyancy of a pressure-treated 4 by 4 fence post. After initial
failure in June 2010, we added a few toggle floats and deployed 4 in the
Gulf of Mexico successfully.
This drifter was designed to provide an easy-to-ship unit all contained
within a Vinyl 4 by 4 fence post (as sold at Home Depot). After initial
failure in June 2010, we adjusted the flotation to successfully deploy 4 in
the Gulf of Mexico.
This drifter was designed to eliminate flotation at the ends of the
sail spars. It uses instead the natural buoyancy of a pressure-treated 2 by 4. After
the initial deployment failed after 3 days, we added four toggle floats and deployed
one in the Gulf of Maine successfully. It is the least expensive, easiest to make, and most environmentally friendly
There are two numbers associated with a deployment. The first is the
"electronic serial number" of the transmitter (typically 6 digits) that
is assigned by the manufacturer. The second is a distinct
deployment "ID". This ID is the key field in the database. While
it was originally a 5-digit number, in the fall of 2009 it was modified
to be a 9-digit number in order to accommodate nation-wide deployments.
This ID is automatically generated based on user's entries in the
web-served deployment documentation. In other words, users will see
what the unique deployment number is after they have entered the
deployment information. It is defined as follows: EXAMPLE: 098430702 is the 2nd drifter dropped in August 2009 at approximately 43N and 070W
- 1st-2nd digits = year ("10" for 2010)
- 3rd digit = month (where all drifters dropped Oct-Dec have a month code of "0")
- 4th-5th digit = latitude (integer degree)
- 6th-8th digit = longitude (integer degree)
- remaining digits = consecutive deployment number associated with this geographic and temporal block
Aretxabaleta, A. L., D. J. McGillicuddy, Jr., K. W. Smith, J. P.
Manning, and D. R. Lynch (2009), Model simulations of the Bay of Fundy
Gyre: 2. Hindcasts for 2005–2007 reveal interannual variability in
retentiveness, J. Geophys. Res., 114, C09005, doi:10.1029/2008JC004948.
Davis, R. 1985. Drifter Observations of Coastal Surface Currents
CODE: The Method and Descriptive View.J.Geophys.Res.,90,4756-72.
J.P. and E. Pelletier, 2009. Environmental Monitors on Lobster Traps
(eMOLT): long-term observations of New Englands's bottom-water
temperatures, Journal of Operational Oceanography. Vol 2-1, p.25-33.
J.P., D. McGillicuddy, N. Pettigrew, J. Churchill, L. Incze,
2009, Drifter Observations of Gulf of Maine Coastal Current,