Oceanetic Model 406 Ice tracking Buoy Manual
Oceanetic Measurement (1989) Limited
Oceanographic Consulting and Technical Support
1695 Mills Road, Hangar 38, Sidney, B.C., Canada V8L 3S1
Tel. (250)656-0535, Fax -0533, E-mail
info@oceanetic.com
03/11/2004
Model 406 Ice tracking Manual, ver 1.1
Oceanetic Model 406 Ice tracking Buoy Manual ...................................................1
Introduction........................................................................................................3
Theory of operation ...........................................................................................3
Deployment .......................................................................................................5
Ideas for deployment .....................................................................................7
* Important Note * ..........................................................................................7
Appendix ...........................................................................................................9
Argos Message Format .....................................................................................9
Table 1- Data format of Argos message packed into 31 bytes. ...................10
Table 2- Converting Argos message data....................................................11
Message Priority Levels ..................................................................................12
Communications Interface...............................................................................13
Downloaded Data Format ...............................................................................14
Table 3- Converting downloaded data .........................................................14
Mechanical Specifications ...............................................................................16
Electrical specifications ...................................................................................16
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Model 406 Ice tracking Manual, ver 1.1
Introduction
This model 406 Ice Tracking buoy is a low cost custom designed platform
designed for the International Arctic Research Center at the University of Alaska
Fairbanks. It has been designed to provide Global Positioning System (GPS)
data both through the Argos satellite network and to internally record data in nonvolatile memory. Originally, the proposal for this buoy included very low cost,
small size and low weight for storage aboard an MBB 105 helicopter.
Theory of operation
The model 406 Ice tracking buoy was designed to provide 10 minute sampling of
GPS data to provide high resolution ice drifting information. The data is
compressed and sent through the Argos satellite system and simultaneously
stored into non-volatile memory.
In order to compress the data to fit the 31 Byte Argos data message, the
positions have been shortened. The first position is the full lat/long with UTC time
from the GPS GGA NMEA string. The subsequent 5 positions contained in the
message are relative positions to the first (absolute) position. The relative
positions are shortened to the difference in the minutes from the latitude and
longitude of the absolute position. The relative positions are taken to 3 decimal
places, and can be a maximum of +/-16.383 minutes. Details for calculating the
relative position can be found in the appendix.
On start-up, the controller will turn on the GPS and try to acquire a position.
Typically, under a “cold boot” condition, new position acquisition will take 2-5
minutes. The Argos PTT will transmit every 180s after start-up. The controller will
pass the PTT a message for transmitting that will include the GPS absolute and
relative data.
The GPS sensor is set up to produce two standard NMEA formatted strings. The
GPGGA and PGRMF strings are sent at 4800 baud, and used to determine the
GPS position, time, date and it's quality. The Garmin receiver sends positions in
degrees plus decimal minutes format and the controller stores and sends position
data in the same format. Although the Garmin receiver gives minutes to four
decimal places, the last decimal place is truncated and is not stored or sent. The
fourth decimal place is equivalent to 20 cm accuracy which is only possible using
differential GPS and post processing.
GPS positions are validated and filtered according to how many satellites the
GPS receiver is picking up, and it's Horizontal Dilution of Precision (HDOP).
Upon acquiring a valid position, the controller then checks to see that at least
three satellites are in view, then verifies that the HDOP variable is less than 7.
Once a valid GPS position has been received the position is written into an Argos
message. The Argos data message (see appendix for details) includes an
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absolute GPS position with a time and date stamp. The following portions of the
message contain the relative position information and a checksum.
Every 10 minutes the controller adds relative position information to the absolute
position in the message. Every hour from start-up a new message is created
while old ones continue to be sent. Every three hours the oldest message is
restarted with a fresh absolute position.
The data is stored simultaneously in non-volatile memory for later recovery. If the
buoy is recovered intact, the data can be downloaded using a terminal program
(i.e. Terra Term, HyperTerminal etc.). Details of this recovery are in the appendix.
Because the buoy is collecting GPS data, it must be deployed in a location where
the sky is not obscured by surrounding topography. This means that the buoy
should be placed on a level patch of ice away from high-pressure ridges if
possible.
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Deployment
The model 406 buoy has been designed to require minimum set-up in the field.
All sampling parameters have been set-up by the manufacturer. It should require
only connecting of power and a brief confirmation of operation, then it is ready to
deploy.
1. The buoy has been built using a standard polyethylene 20 gallon container for
the hull. The buoy must be opened to connect the power to be turned on.
Remove the nylon strap from the lid and turn the lid counter clockwise to
open.
2. Undo the two ¼" wing nuts that hold the aluminium ground plane in the buoy.
Ground Plane
Argos Antenna
Wingnuts
GPS Receiver
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3. Gently lift one side of the ground plane to lift the plane off the ¼” studs. Care
must be taken with this as the Argos and GPS antennas are both hardwired to
the controller and the short cables and their terminations can easily be
damaged by excessive force.
Ground Plane
Argos PTT
Controller Box
Battery Harness
4. Check all other connectors on the PTT and controller box. DB9 and DB15
serial connectors should have the locking screws checked and tightened if
necessary. The BNC connector to the Argos antenna must be secure before
power up.
5. Find the power bridle and attach first to the 5 20 Ah battery connectors
coming through the blue foam.
6. Place the Oceanetic passive Argos beeper within 3 metres of the Argos
antenna. It will beep loudly when the buoy transmits.
7. Turn on the Telonics TSUR-400 uplink receiver and have handy nearby. It
should be able to receive the buoy from over 20 m, but obstructions will limit
its range. In particular steel structures such as ship bulkheads will interfere
with reception.
8. Plug in the last connector on the bridle to the connector on the controller box.
The buoy should transmit in 180 s. Check a watch for the time and listen for
the beep from the OML beeper and the tone from the Telonics TSUR-400.
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The Telonics set should display the time of transmission, PTT ID and any
data sent. Refer to the appendix and the TSUR manual for details. The GPS
will require 2-5 minutes to acquire a good position so it will not appear in the
data until that time.
9. Press ground plane back into position, do up the wing nuts and replace the
lid. The buoy should now be placed on deck where it can acquire a GPS
signal and start collecting data. The TSUR-400 can be used to view received
data. See TSUR-400 manual for set-up information.
10. Once the buoy has been powered up and routine operation has been
confirmed, it is ready for deployment. It is recommended that you start up the
buoy 1-2 days before deployment to check operation. There is sufficient
battery to cover a generous test period and a 2-month deployment with a
good safety margin.
11. On recovery, the battery connectors in the buoys should be disconnected
immediately to prevent memory overwrites and further Argos transmissions.
Refer to the Communications Interface section for data download instructions.
Ideas for deployment
1. Line of sight – Both Argos and GPS rely on satellites for communication by
radio. It is important that the buoy have an unobstructed view of the sky for
operation. Avoid placing next to pressure ridges or operating inside labs or
hangars on the ship.
2. Ice ablation – A typical problem of placing instrumentation on ice or snow
covered surfaces is that the instrument may absorb more solar radiation
than the surrounding white surface. The result of this is that it may cause
increased snow or ice melt under the buoy. Since the buoy is yellow, this
should be less of a problem than with darker colours. It is a good idea to
place a ¼ sheet, 2’ x 2’ piece of white painted plywood under the buoy at
the deployment site. This will also reduce the effect of wind scouring if the
buoy is placed on a layer of snow.
* Important Note *
The 6 buoys to be deployed from the Polarstern in November 2004 have a
programmed feature that requires another step in set-up. The controller has been
programmed to not use up battery power if GPS reception is not found within 5
minutes. The controller will go into a sleep mode and try again in 10 minutes. The
GPS however needs to have a position received within 2 weeks to act as a seed
position for calculating its position. If it does not have a recent position, it will go
through a set-up period that may take more than 5 minutes. It is necessary
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therefore to turn the buoys on and acquire a GPS position within 2 weeks of 25
October (before 8 November) to provide the needed recent seed position.
Alternatively, the GPS must be started independently and a new position
acquired. The DB9 connector on the GPS is not a standard serial connector and
has power on pins that may damage a PC if connected. It requires the special
interface connector made of a DB9F and DB9M with the power leads brought
out. The interface can either be used with the spare 20 Ah alkaline buoy battery
or other 12 V (6-40 VDC) source. The interface requires a standard serial cable
to the PC.
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Model 406 Ice tracking Manual, ver 1.1
Appendix
Argos Message Format
The model 406 Ice tracking buoy was designed to provide 10 minute sampling of
GPS data to facilitate high resolution ice tracking. The data is in hexadecimal
format, compressed and sent to the Argos satellite system. In order to compress
the data to fit the 31 Byte Argos data message, the positions have been packed
together. The first position is the full lat/long with UTC time from the GPS GGA
NMEA string. The subsequent 5 positions contained in the message are relative
positions to the first (absolute) position. The 5 relative positions have been
shortened to the difference in the minutes of the latitude and longitude of the
absolute position. This relative position is taken to 3 decimal places. See Table 1
for a description on how each byte is packed into the message. See Table 2 for
details on how to extract the Argos data to usable data.
Using the Telonics Receiver
The Telonics TSUR-400 uplink receiver is used to receive Argos PTT
transmissions in a local area. When the uplink receiver is in “split bit” mode it will
display the buoy data with each field separated as shown in this table. When
viewing on the screen, note must be made that the display can scroll down but
not up again. If a lot of data is desired for converting, it is best to set up a log on
the uplink receiver and then download to a computer.
The Telonics receiver has already been set up in split bit mode for the 406 buoy.
When a message is received, you will see the buoy PTT id number appear on
the screen. When using the scroll down button, two columns of decimal numbers
will appear. The leftmost column is the field number, and the one to the right is
the data in that field. The first field is the message identification number, the
second field is battery Voltage (unused at this time), the third field is UTC day,
etc. Refer to table 2 for more details.
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Model 406 Ice tracking Manual, ver 1.1
seconds- 6
s
s
s
s
s
s
5
d
d
d
d
9
m
m
13
long degrees- 8
d
d
d
d
day- 5
d
d
m
12
m
m
m
m
m
m
Field Description- # of bits
Byte Contents
Byte Number
m
16
m
m
m
m
m
m
Field Description- # of bits
Byte Contents
Byte Number
m
20
m
m
m
m
Field Description- # of bits
Byte Contents
Byte Number
m
24
m
m
Field Description- # of bits
Byte Contents
Byte Number
m
28
sign- 1
sign- 1
sign- 1
sign- 1
Field Description- # of bits
Byte Contents
Byte Number
s
s
s
s
d
lat degrees- 7
d
d
d
d
d
d
d
minutes- 16
m m m
m
m
m
m
relative minutes long 2- 14
m m m m m m
17
relative minutes long 4- 14
m m m m m m
25
m
29
m
m
2
m
year- 6
y
y
minutes- 16
m m m
6
relative minutes long 1- 14
m m m m m m
relative minutes long 3- 14
m m m m m m
21
relative minutes long 5- 14
m m m m m m
mth- 4
m m
d
s
d
y
y
y
m
m
m
m
m
m
7
m
10
m
m
m
m
m
m
m
m
11
m
14
m
m
m
m
m
m
m
s
15
m
m
m
m
m
18
m
m
m
m
m
m
m
m
m
m
22
m
m
26
m
m
m
m
m
m
m
m
m
m
m
m
m
hours- 5
h
h
3
y
s
chksum- 8
c
c
c
30
Table 1- Data format of Argos message packed into 31 bytes.
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s
s
c
h
h
m
m
m
m
s
s
c
m
m
relative minutes lat 2- 14
m m m m m m
relative minutes lat 4- 14
m m m m m m
23
c
minutes- 6
m m m
m
m
m
relative minutes lat 1- 14
m m m m m
relative minutes lat 3- 14
m m m m m m
19
relative minutes lat 5- 14
m m m m m m
27
c
h
sign- 1
v
1
sign- 1
v
sign- 1
s
8
m
v
sign- 1
m
v
sign- 1
m
4
voltage- 7
v
v
v
sign- 1
Field Description- # of bits
Byte Contents
Byte Number
m
sign- 1
Field Description- # of bits
Byte Contents
Byte Number
m
0
sign- 1
Field Description- # of bits
Byte Contents
Byte Number
msg id- 2
Packed Argos Message Description
m
m
m
m
m
m
m
m
m
m
m
m
m
m
c reserved by PTT
31
Model 406 Ice tracking Manual, ver 1.1
Argos data will come separated in bytes either in decimal or hexadecimal. A
decimal number will range from 000 to 255 and a hexadecimal number will range
from 00 to FF. Both should be padded with leading zeroes. Starting at the most
significant bit of the Argos data (in the first byte), GPS data is decoded into a
number of fields as follows:
Table 2- Converting Argos message data
Field
Number
1
Number
of bits
2
Field description
2
7
Message
identification
Voltage
3
5
4
Field Range
Field Conversion
range 0 to 2 (decimal)
Convert to decimal
Convert to decimal
UTC day
Unused in this version
of firmware
0 to 31 (decimal)
Convert to decimal
4
UTC month
0 to 12 (decimal)
Convert to decimal
5
6
UTC year
0 to 63 (decimal)
Convert to decimal
6
5
UTC hours
0 to 23 (decimal)
Convert to decimal
7
6
UTC minutes
0 to 59 (decimal)
Convert to decimal
8
6
UTC seconds
0 to 59 (decimal)
Convert to decimal
9
7
0 to 89 (decimal)
Convert to decimal
10
16
Absolute degrees
latitude
Absolute minutes
latitude
0 to 59,999 (decimal)
11
1
12
8
Convert to floating point (3
decimal places), divide by
1000
1 = North
0 = South
Convert to decimal
13
16
14
1
15
1
16
14
17
1
18
14
19
1
20
14
21
1
Absolute latitude
sign
Absolute degrees
longitude
Absolute minutes
longitude
0 to 1
Absolute longitude
sign
relative latitude
minutes (1) sign
relative latitude
minutes (1)
0 to 1
relative longitude
minutes (1) sign
relative longitude
minutes (1)
0 to 1
relative latitude
minutes (2) sign
relative latitude
minutes (2)
0 to 1
relative longitude
minutes (2) sign
0 to 1
0 to 179 (decimal)
0 to 59,999 (decimal)
0 to 1
0 to 16,383 (decimal)
0 to 16,383 (decimal)
0 to 16,383 (decimal)
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Convert to floating point (3
decimal places), divide by
1000
1 = East
0 = West
1 = plus
0 = minus
Convert to floating point (3
decimal places), divide by
1000
1 = plus
0 = minus
Convert to floating point (3
decimal places), divide by
1000
1 = plus
0 = minus
Convert to floating point (3
decimal places), divide by
1000
1 = plus
0 = minus
Model 406 Ice tracking Manual, ver 1.1
Field
Number
22
Number
of bits
14
23
1
24
14
25
1
26
14
27
1
28
14
29
1
30
14
31
1
32
14
33
1
34
14
35
8
Field description
Field Range
Field Conversion
relative longitude
minutes (2)
0 to 16,383 (decimal)
Convert to floating point (3
decimal places), divide by
1000
relative latitude
minutes (3) sign
relative latitude
minutes (3)
0 to 1
relative longitude
minutes (3) sign
relative longitude
minutes (3)
0 to 1
relative latitude
minutes (4) sign
relative latitude
minutes (4)
0 to 1
relative longitude
minutes (4) sign
relative longitude
minutes (4)
0 to 1
relative latitude
minutes (5) sign
relative latitude
minutes (5)
0 to 1
relative longitude
minutes (5) sign
relative longitude
minutes (5)
0 to 1
message checksum
0 to 1
1 = plus
0 = minus
Convert to floating point (3
decimal places), divide by
1000
1 = plus
0 = minus
Convert to floating point (3
decimal places), divide by
1000
1 = plus
0 = minus
Convert to floating point (3
decimal places), divide by
1000
1 = plus
0 = minus
Convert to floating point (3
decimal places), divide by
1000
1 = plus
0 = minus
Convert to floating point (3
decimal places), divide by
1000
1 = plus
0 = minus
Convert to floating point (3
decimal places), divide by
1000
Convert to decimal. This is the
8 bit arithmetic sum of all 31
bytes in the Argos message
0 to 16,383 (decimal)
0 to 16,383 (decimal)
0 to 16,383 (decimal)
0 to 16,383 (decimal)
0 to 16,383 (decimal)
0 to 16,383 (decimal)
Message Priority Levels
It is desirable in an Argos Application to have has as much data overlap as
possible to ensure that the data is received by satellite. The following message
sending protocol has been developed in an attempt to get a high level of
confidence in receiving all data, given that the longest interval between satellite
passes may be as much as 3 hours, with an average of 1.5 hours.
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Communications Interface
The buoy controller has a limited capability to communicate with a “dumb
terminal” or a terminal emulator running on a Personal Computer (PC). This
interface enables the user to download stored data (to be logged to a file for
example), dump memory contents at various addresses, or begin the data
acquisition cycle.
PC/terminal interface requirements are as follows:
•
•
•
•
•
•
•
PC or terminal with an RS-232 compatible interface
19,200 baud
8 data bits
no parity
1 stop bit
Hardware/Software handshaking disabled
RS-232 extension cable (straight-through cable). Should be no more than
regular length (a few feet or so).
GPS Connector (not RS-232)
PC Connetor (RS-232)
PTT Connector
To communicate with the controller:
1. Set-up your PC with a terminal emulator such as Hyperterminal with the
communication settings listed above. Set up the program to log incoming
data to a file.
2. Connect the RS-232 cable to the PC, but do not connect it to the controller
yet. Make sure the battery connector is detached from the controller box.
Leave it disconnected for at least 10-15 seconds to allow the circuit time to
discharge.
3. Refer to the above picture to help locate the PC connector on the controller.
Connect the RS-232 cable to it.
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To download data:
1. With the Terminal emulator program running, plug the battery connector into
the controller box. Hit any key within 5 seconds of powering up the controller.
The controller will go into communication mode when it detects a keystroke
within the first 5 seconds of power-up. After that, it will enter its acquisition
mode.
2. A prompt will pop up on the terminal display:
Command: go dp dl >
If the terminal emulator is logging data to a file, you are ready to download
the memory contents. Type in the letters dl (lower case) to begin. The
controller will send the contents of the first memory chip. When the first chip
is done it will prompt to download the second then the third memory chip. At
these prompts, you will have the opportunity to log to a new file. To resume a
download hit any key.
Note:
The dl utility in the controller is provided as a simple way to obtain data from the
internal memory. No method of error checking is implemented with it, so we do
not guarantee the accuracy of the data. The user should look over the following
section and scan the data for anomalies that may appear.
Downloaded Data Format
Data is downloaded from controller memory in a Comma Separated Value
format. As hexadecimal values are pulled from memory they are formatted and
printed to the terminal as decimal numbers. Each row represents a time/date
stamped GPS position. The first row of characters are abbreviated field titles
only. Here is an example of the first couple of lines of a CSV output:
Command: go dp dl >
Hit Backspace to pause download, hit Enter to restart
Rec#,Date,Time,LatD,LatM,LatM,LatS,LonD,LonM,LonM,LonS,SIV,HDOP
00000,012,010,004,000,015,004,075,000,000,000,120,005,255,001,003,001
The last row of characters is the first data set from memory. The leftmost value
is the five-digit record number. It ranges from 0 to 4096 (decimal), and is padded
with leading zeroes. The following 16 values are the decimal representation of
GPS data, range in value from 0 to 255 and are also padded with leading zeroes.
In the above example the values 00000,012,010,004 represent record number 0
and a three number date code (dd/mm/yy) of 12-October-04. The table below
describes the 16 data values:
Table 3- Converting downloaded data
Field
Number
1
Field description
record number
Field Conversion
none
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2
UTC day
none
3
UTC month
none
4
UTC year
none
5
UTC hours
none
6
UTC minutes
none
7
UTC seconds
none
8
Absolute degrees latitude
none
9
Absolute minutes latitude (upper byte)
10
Absolute minutes latitude (lower byte)
11
Absolute latitude sign
12
Absolute degrees longitude
convert to 16 bit unsigned integer,
multiply by 256
add to field 9, then divide this result by
1000 to get decimal minutes
1 = North
0 = South
none
13
15
Absolute minutes longitude (upper
byte)
Absolute minutes longitude (lower
byte)
Absolute longitude sign
16
Satellites in view
convert to 16 bit unsigned integer,
multiply by 256
Add to field 13, then divide this result by
1000 to get decimal minutes
1 = North
0 = South
none
17
HDOP
none
14
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Mechanical Specifications
Physical dimensions
Maximum diameter: 58.40 cm (23”)
Height: 48.25 cm (19”)
Weight: approx 16 kg (35 lbs)
Electrical specifications
Battery capacity
Approx. 100 Ah (at 0C) 12V alkaline battery
Argos PTT
Seimac Wildcat
1.1 W output
180 s transmission repetition rate
GPS Sensor
Garmin 16 (12-channel receiver)
Sampling rate
GPS positions are taken every 10 minutes and stored and transmitted via Argos
in messages of 6. The latest 3 complete messages are sent in rotation to ensure
reception during a pass of the satellite.
Endurance
EEPROM memory is capable of holding 85 days sampling at the above rate.
Battery estimated to be sufficient for up to 85 days (at 0C).
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