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GPS / VHF & Your Boat |
WHAT IS GPS ? Global Positioning System is a worldwide Satellite Navigation System. It is funded by and controlled by the U. S. Department of Defense (DOD). While there are many thousands of civil users of GPS world-wide, the system was designed for and is operated by the U. S. military. It is a US Government run system that uses these "man-made stars" as reference points to calculate positions to interface with your receiver, & by utilizing 3 or more at a time, it can pinpoint your location accurately to a matter of feet. To "triangulate," a GPS receiver measures distance using the travel time of radio signals. It can tell your speed also. If your receiver is properly set it can even tell elevation.
Have you ever wondered how your cellular phone company knows when you are in "Roaming"? When it is tuned on, these phones have a built in GPS receiver that relays where you are to the cell phone server. Many service businesses now equip their vehicles with GPS, so the driver can locate a customer, or the dispatcher of a large freight company knows where his trucks are & can dispatch a truck to a destination that he is close to to pick up a newly called in order. Carrier-phase tracking of GPS signals uses special receivers & has resulted in a revolution in land surveying, where it can pinpoint a section corner to within a quarter of an inch.
Marine use GPS uses Latitude & Longitude in Degrees and Minutes to the third decimal place, which can pinpoint where you are. Engineering GPS carries it to the forth place for finer location. Latitude is numbers that run North & South, while Longitude are East & West. In the early days of GPS, the last set of numbers only read in 2 digits, more recently the receivers are reading in 3 digits. This 3rd digit just pinpoints you that much more precisely, like nickels instead of dollars. As of May 02, 2000 Selective Availability (SA) was discontinued. Prior to that date, the military randomly scrambled some of the signals to help protect our "Homeland Security". You may have been on one time but the next 1/2 hour it could be off by up to 100'. After that date "Selective Availability" was eliminated & now you will be within 10'.
| Lowrance 7500c GPS/Plotter unit | Lowrance iFINDER20 |
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| This unit is a stationary mount plotter & GPS | Here is a hand-held unit |
Now to confuse you, there is a difference in marine charts / Google Earth readings than your handheld or GPS that is mounted in your boat. These chart numbers are true Longitude & Latitude using divisions of 60. However with the advent of GPS, a 60 second division does not compute, (or the government engineer behind it was not aware of the old system). Kind of like your micro wave, where 100 equals 60 seconds or 1 minute.
Your GPS translates in 100s. This means that if the minutes & seconds are now divided by 100. The degrees appear to stay the same, just the minutes & seconds are now a finer calibration in to .10 of a minute as compared to .1666.
If you used the third set of numbers taken off a chart that read 1/2 a second (in GPS numbers it would be 500).
you would have to multiply that by 1.666 to come up with the equivalent GPS numbers, or 666. However either will usually be close enough to get you within visible sighting of the buoy, etc.
When using the FISH.n.MAP CO. charts they have in a corner of this chart marked divisions of 10 in a minute area with a note that "Chart is scaled using NAD 83 for the Datum -- Each small division equals .10" (Minute)".
As an example by using the information below, you can calculate your approximate position in relationship to another position
Longitude (East/West
measurement) --- using
Westport North Jetty West 124-11-078 as a reference
1 degree = 60.7 Nautical Miles at the equator 124
7525.8 NM west of datum line of Grenich Village
(England)
1 minute = 1 Nautical Mile (6071') 124-11 11
NM west of 124-00
1 second = 60.7' 124-11-0 0
feet west of 124-11
.010 of a second = 6.07' 124-11-07
7/10ths of a second or
42.49 feet west of 124-11-0
.001 of a second = 7.28" 124-11-078 8/100ths
of a second or
58.24 inches west of 124-11-07
Latitude (North/South
measurement) --- using
Westport North Jetty -
North 46-55-540 as a reference, uses the same basic principle as
Longitude, but 00 is the Equator
Westport North jetty
46-55-540 / 124-11-078
Westport Buoy #5
46-54-820 / 124-12-700 (1 mile &
4127.6') = approx. 1 5/8 miles west
& 3/4 of a mile south of the north jetty
For instance if we use Westport Washington's buoy #3 as your position (46-55-005, 124-14-820), we see the Latitude as the first set of numbers, with the Longitude as the second set. For Latitude, the numbers get larger as they go farther north, & the Longitude get larger the farther west you go. So from this you can quickly calculate if your friend calls you on the radio & says he is at 47-10-501, 124-24-802, if you compare his numbers to yours, this means he fairly close by & is slightly north & somewhat west of you.
You can enter a GPS numbers from a friend or a chart & set your GPS to "GO TO" those numbers & your unit will direct you by a compass course directly to that location. If you drift off slightly it will re-calculate your go to compass course & help you correct your heading. Depending on the brands, when you get there a bell will ring usually within a tenth of a mile & another bell when you have arrived. You can make a run in the fog & if coming back in, be precise in returning to your waypoint buoy if you are say returning to the harbor if you follow the trail of "mouse tracks" where you had been before. These "GO TO" of course does not take into account for jetties or other land obstacles in between, unless your unit is also a plotter which shows a map with your position being a blinking dot.
You can then program your unit so that your "go to" destination will read distance from your current location. Some will even give you an estimated arrival time by calculating your average speed. Most will also give you a overall distance traveled that can be reset.
Most of the units now have incorporated maps that overlay your boat position on the map. This is usually called a GPS/Plotter. As you move around on the water, your "boat" is indicated by a blinking dot or a triangle, that also moves on the chart in the direction you are going. If it is the one with a triangle, the pointed end will be your bow & the triangle will move in the direction your boat is moving.
With the GPS & a Plotter, life has gotten a whole lot easier for the mariner. This is very useful when navigating a small river channel that leads thru a bay where the tide fluxuates & sandbars exist.
Many GPS units use "Mouse Tracks or Trails" which are simply dots or lines on the screen shown as a trail where you have been. If you catch a fish in one location & circle around to try for another one, you can see the trails on the screen. Some units you can designate the color of the trails. this works great if you want to keep your trails from last week & have a different color for this week. You can delete them if & start over if they get to where they clutter the screen.
You can manually enter your Waypoints, or if you are motoring by a buoy & want to record it's location, on most units, by hitting Waypoint button twice in rapid succession, will enter that GPS location at the units "001" or successive higher number depending on how many times you have used this alternative. You can then later call "001" waypoint up & change the name to what you desire, & it will be in your system. I usually keep a paper scratch pad handy to document the location number so I can remember later. On most units you can select a Icon from many available for your waypoints. These could be a symbol of a boat being launched, an anchor, a stop sign, a buoy, a house etc. & they help you differentiate between the many possible waypoints you may have on the screen.
Some units allow you to move the curser on the screen & when you get it to the Longitude & Latitude, push either the Enter or waypoint button which saves that location as a waypoint. You can then go back in & edit it by naming it & if need be fine tune the L&L numbers.
One thing I do if I am running down a river channel & encounter a dead-head instead of punching in a waypoint, I just circle around it in a tight circle & then on the screen it will now show mouse tracks to identify this location. I can then go back later & manually move the curser to this location & create a informational waypoint for it if I want to.
Most units have a function that is called a "Man Overboard" function. This is a button or combination of buttons you can use to mark a spot where you caught a fish, & want to go back to the same location. Some allow you to punch a button to record a location where you caught a fish. The units will assign their own number to this location. So if you use this feature a lot, you will then have remember which is which & transfer the ones you want to save to your main number section.
You can set up "Routes" where you want to go out the harbor to a certain buoy, then change course to a different buoy, & then on to your fishing grounds. If you set it up right, when you start out to the first one, the unit will automatically change to the next "GO TO" once you are there, until you have arrived at your last location.
I have found that in naming the waypoints, that it is best to establish a numbering system, because if you happen to be running a coast-line & are marking buoy numbers, you may have duplicates which can complicate things. Even if you name them like Gary's hole or Jim's hump, unless you remember, it is hard to locate a waypoint quickly when you are running on the water & trying to make your unit do what you want it to do. I also try to number mine in groups of 10 ish starting in my northern most location & working south. It becomes less of a issue if you then want to place another new waypoint in without having to retype the whole name. So what I do is set up "10", "20", "30" series routes, but I leave 2 blank spaces after these first "20" numbers for possible "A or B" waypoints. This way I do not have to retype the whole name, but simply change the first numbers. I then may have "24A & or 24B" inserted between the 24 & 25 numbers. So instead of limiting my route to only 10 waypoints, I may actually have 15 or 20 that are in sequence, readily identifiable & usable.
One thing that I may be misleading you here is that you do have to steer your boat where the GPS is directing you to go UNLESS you have an "AUTO PILOT". The GPS just gives you a direction as to where to go.
For those of you without a lot of dash room on your boat, there are units now that are a combination of GPS/Plotter & Depth Finders. On these you can by pushing the right buttons & in the right sequence split the screen so that you can see both these navigation aids at the same time on the same screen.
One thing that is beneficial if you are considering a purchase of these units is to take a second look at the new color units. Sure they cost more, but in my book are worth it. The reason is that if you have a mono-color unit mounted where the sun is shinning on it or at a slightly wrong angle to your helm, the image on the screen can be about impossible to see. These new color units have been improved to the point that the extra bucks are worth it at the time of the initial purchase & you can see them from many angles, even from the back of the boat.
These newer units usually have a built in map system showing water depth footage, sunken ships, buoys, etc. If your needs are greater than this depending on the unit you purchase, you can purchase a small memory card that will allow you to load it into your unit & be able to view MANY more precise details. However these cards are not inexpensive.
You usually can select from a "Main" or "Pages" menus for many different configurations. One page may give you time, speed over ground, water temperature, distance, estimated time & compass heading to your designated selected location. Life has gotten complicated, but well worth the effort to learn your unit, because some day it may just save your life.
Look & Ask Before You Buy : I suggest that you do a lot of looking before you make a purchase that after spending a lot of hard earned cash that you find a friend's unit may be a lot more user friendly, or has options that you like better for your style of fishing. By looking, I mean go to a store that has many different brands & models on working display. Ask the salesperson to explain & show you how the unit that you initially have picked out works. Little things do make a difference in situations like this. Can you get the speed & temperature to show on the main screen while using a GPS/sonar at the same time, or do you have to go back to a "Menu" page to get this data to show, while loosing one of your main screens.
I had a problem on one of my newer units whereby when running down a narrow river channel using the GPS plotter, I would loose the depth footage. Not a good thing when you are in 8' of water & the channel is shallow. I found if I slowed down it would recover the footage. The next spring at a sportsman's show, I talked to a sales rep. After thinking about it for a bit, he said to go into the menu & increase the "Ping Speed". Apparently in deeper water the sonar cone would be wider & would bounce back to the transducer in time to respond. But in this shallow water the cone was so confined that by the time the echo got sent back up & I was going fast enough that the echo was coming up behind the boat. This was something that was not even discussed in the owners manual.
GPS Antenna : Many of the new units can be purchased with a "built in antenna", while others can be had with an external antenna. Some boaters like the more compact packages of the internal antenna, & this can be a benefit for a small open boat. Others with this option may complain that depending on the boat's top, that they occasionally LOOSE contact with the satellites.
With the internal antenna units, if your antenna goes bad, your GPS is essentially DEAD until you send it in for repairs & get it back. This WILL happen during the best fishing time & of course during your planned vacation. Been -There -Done -That, more than once.
However, if you talk to enough fishermen who use GPS, & even have the external units, you will find that the most common failure is that the antennas themselves are the most often failure. Therefore if you can find a unit that uses an internal antenna AND the plug in for usage of an external antenna, you have the choice of having a back-up antenna.
Therefore if your unit has the provision for an external antenna, plus the built in one, you have the best of both worlds & a backup
Now if you have the external antenna model, just a simple antenna replacement gets you going again. Depending on your needs, here may well be the time for redundancy of having a second antenna already mounted, but not hooked up until needed. Even just having a second one aboard as a spare may be a good idea, as we trend to get to where we rely on our electronics way more than we should. You may have to find out if you would have to go into your unit's setup mode & select the antenna you intend to use.
Also if you are using a external antenna, it is suggested to have it mounted out of the way, but in a area where it always has a clear view of the sky. I do not like having an antenna mounted on the gunnels, where it is prone to being bumped, tripped over, having the mooring lines tangled, always in the way etc. Shown on the photo below is one method of achieving the out of the way part. Here the cable is tucked under the vinyl top & ran down inside the corner frame being attached by running thru a couple of plastic "P" clips screwed to the inside of the window frame.
| GPS external antenna mount |
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Computer Downloadable : Many of the newer high end units are now compatible with computers. This may mean that you can call up a chart on your computer, plot your course with waypoints & then download it into your GPS boat unit. This is many times easier than punching in the many hundreds of waypoints by hand as before.
Many of the new makes/units offer a computer download that you can simulate the exact things you will see on your unit in the boat. It may well save time & frustration to download a couple different programs so that you can get a feeling of how they operate BEFORE you lay down your credit card.
Some will even allow you to upload from your GPS unit, the history of your trip so you can then look at where you were fishing & record where you caught the big ones.
One thing that amazes me is that one of the leading manufacturers does not provide for downloading GPS locations off a computer onto a SD card & downloading, making you enter all on the unit itself. For freshwater fisherman this may be fine, but a saltwater fisherman who covers 100s of miles of coastline that needs many locations like buoys, submerged rocks plus all the fish hot spots this is the pits.
Shown in the picture below is a combination GPS & Depth Finder unit. Where space is a constraint, these type of dual units may be worth considering. Here you could split the screen as shown, displaying both. Or if you did not need the GPS like when on a small lake, you could revert back to a single screen for each if needed with the push of the button.
| Lowrance LMS
337c GPS/Plotter-Depth Finder showing a split screen with GPS on left &
sonar on right |
Garmin 441s which is a combo GPS/ sonar. Here the sonar is on the bottom of the screen |
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In the old days before GPS, we used charts (sometimes) of our area, the compass (sometimes) & the depth-finder (sometimes), & we learned to navigate even in the fog. This is at times called "Flying by the Seat of Your Pants or Dead Reckoning" & means that you have to do plotting courses, figuring a current or wind drift, the speed of your boat from point A to point B which relates into time to cover the distance using a compass course. Scary sometimes in the fog, but we managed. The one important thing was we had to be aware of the current & wind drift & where we were at all times. We had to be sure we were either north of the harbor entrance or south of it if the drift or wind was prevalent, which direction, because if when we ran back in toward shore in the fog thinking we were north & had actually drifted to the south when fishing, we were REALLY south to start home, we could be WAY off from where we thought we were & going the wrong way by the time we realized something was wrong. We would normally run toward shore, (here, that meant East) & when we came to the shallower water near the beach (30') we simply followed that depth line in the direction we figured was home port until we came to the deeper river channel & turned into it going up the river to the boat basin.
If you get into the habit of relying on your electronics & for whatever reason they malfunction, you can be in a bad situation if you are not prepared. I had that happen one morning upriver on low tide at Westport when we ran into a shallow cove upriver behind the flats to pull our crab pots before heading out to salmon fish. There were other commercial pots there with lots of line floating, we got ours pulled & back in, then it fogged in. As we got ready to head out my GPS plotter quit. We were far enough inland that the radar was pretty well inoperative. It took slow running in the direction of the channel & then guestimating how far we were from Ocean Shores before heading west & out of the bay. Finally the radar picked up the south jetty & we were oriented. Then of course the GPS came back on.
The above being said, if you are not using this GPS method of navigating either to known buoys, back to the marina or to fishing locations, you are missing a lot & could be putting yourself in danger. However if your method of fishing is in small impoundments or in rivers that satellite guidance is not required, then you can spend your money on other needed boating things.
VHF Radio -- The initials stand for Very High Frequency. This is a radio system used strictly for marine usage. Normal distance of communication is about 20 to 25 miles line of sight. If there is a large hill between you & the other boat, chances are you will not be able to communicate with them. Normally, the taller the antenna the farther you can reach because this radio is line of sight & the curvature of the earth limits transmition. Normal ship to small ship transmition will be limited as compared to a ship to a land based tall antenna like a US Coast Guard base. And a ship to at least another which may have a taller antenna mounted on the top of the cabin will of course be able top receive better than a ship that has only a 3' antenna.
VHF radios are made in fixed mount type for affixing to a dash or close to a skippers area, or a hand-held unit for more mobile usage. The hand-held will not normally reach as far as a fixed mount, simply because of the smaller antenna. Some of the brands normally seen may be Standard Horizon, Uniden, Cobra, Icom or West Marine.
| Modern VHF fixed mount radio | Hand-held VHF unit |
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VHF radios are the main communications for the US Coast Guard using channel 16. There are dedicated channels for certain types of communication, Coast Guard, commercial traffic, normal recreational traffic, etc. Listed on the following link is the US Homeland Security, Coast Guards listing of VHF channels CLICK HERE
Currently most VHF radios are very similar in operations. Most will have a dual power setting, 1 watt & another at 25 watts of transmit power. The lower power is to be used for communicating with your other boaters when you are in close proximity of each other, like a boat basin so you don't blast everyone near. The 25 watt is for more normal longer transmit usage distances.
Some radios have what is called Dual Watch, which means you can monitor say the Coast Guard channel 16 plus a fishing channel of possibly 68. Others have a Weather Watch, which allows the radio to automatically break in if a NOAA storm warning is broadcast in your area.
All VHF radios now have Marine Weather channel capability, of which usually one will be for an area near you. These are continuously being played & are updated about every 12 hours.
Digital Selective Calling / Maritime Mobile Service Identity : DSC radio is the latest in marine radio technology. DSC is part of a global upgrade in maritime distress communications. Satellite and digital technology used for several years on commercial ships is now available to the recreational boater.
Radios with DSC capability have been on the U.S. market since 1999, the Federal Communications Commission (FCC) has required new fixed mount models introduced in the U.S. to be equipped with the DSC feature. Minimally, DSC radios are equipped with single-button emergency transmission capability. The earlier SC-101 class radios have been largely replaced by superior Class D DSC radios.
DSC radios have a one-button emergency transmit button that sends the vessel's unique MMSI number. Similar to a cell phone number, it is your unique calling number for DSC VHF. Your MMSI number is transmitted with a DSC call, like “caller ID.” In addition, if the DSC equipped radio is linked to a GPS or Loran unit, the distress call will include the vessel's position. Should the skipper become incapacitated, the radio will continue sending the mayday.
When initially setting up your unit, you need a connector cable from the GPS unit to the radio. This cable has a single male plug that goes into the radio & attaches to 2 wires from the GPS. You will have to read the owners manual to tell which color coded wires from the GPS attach to the red & black radio wires. Then you may have to go into the "Menu" section of the GPS & select NMEA 0183 output as the proper com port 1 export code. If you have everything right, when you turn on your radio, the GPS latitude/longitude you are at will read on the screen of your radio along with the selected channel.
The Coast Guard urges, in the strongest terms possible, that you take the time to interconnect your GPS and DSC-equipped radio. Doing so may save your life in a distress situation! They also want any vessel equipped with a VHF when on the water to have the radio on & available to receive channel 16. the best way to accomplish this is if your radio has a "Dual Watch" capability, to tune it to your regular monitored channel, like 68 & then push the dual watch button & the radio will automatically scan just these 2 channels. This is so that if you happen to be in a location where there is a boating emergency, you will hear the call. If you happen to be closer than a Coast Guard boat or plane, it is your duty to respond.
Since 1996 recreational boaters were no longer required to have a ship's station license issued by the FCC in order to operate a VHF radio. However the new DSC radios however have to be registered to work properly in emergency situations. They are also encoded with a unique nine digit FCC identification number that allows the ship-to-ship calling feature. This unique number called a Maritime Mobile Service Identity or MMSI, is much like your cell phone number. Once the radio is registered with the FCC, (which is free) your boat's information (that you supplied when you got your MMSI number) is entered in the US Coast Guard's national distress database.
The major advantage of the DSC radio is its ability to send an automatic "mayday" that identifies the vessel and also, when connected to a GPS, can send the vessels location. The DSC radio operates much like an EPIRB that sends encoded "maydays" directly to satellites.
Another feature of the DSC radio is the ability to place private ship-to-ship calls to other vessels equipped with DSC radio. Basically if you know the MMSI number of the radio you are calling only that vessel will receive you message. Just like using your cell phone.
Although commercial ships over 300 tons are now required to monitor the DSC Radio reserved Channel 70 for distress calls, the US Coast Guard is still monitoring Channel 16 plus channel 70. Listed below are outlined the benefits of this.
DSC capability to send or receive calls on channel 70
The DSC radio feature is part of the Global Maritime Distress and Safety System (GMDSS). This system was put in place by international treaty in 1988 and all seagoing nations including the US will be GMDSS compliant by 2005-6.
Winter Storage : One word of caution, when you leave your boat for the winter months in any kind of storage, it is best to remove all of your electronics & keep them inside in a dry location. Sure they are water resistant (or supposed to be somewhat) but if left in a damp environment unattended for any length of time, when you try to start things back up in the spring, you may have problems.
If your boat is a aluminum version & you store it during the winter in a unheated building (or worse outdoors) depending on the weather conditions, you may well experience sweating inside the boat. This can also be transferred to your electronics. Also remember to remove your paper charts as they tend to get damp & cam mould. If you keep your manuals for the motor or electronics on the boat, place them in zip-lock bags.
It would also be beneficial (depending on your locality) to install a portable electric heater in the cabin or under the cover during the winter months.
Copyright © 2004 - 2011 LeeRoy Wisner All Rights Reserved
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Originally Started 05-2005 Last updated 05-22-2011
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