GPS and Chartplotters
I was researching GPS and Chartplotters for my boat. This page is a result of my research.
Functions and features are offered in gay abandon by gps manufacturers and it's complicated to make sense of what is out there. All the manufacturers offer different models and wax poetic about their gps units. Here is some help. It is not all inclusive, nor do I intend to compare and contrast different brands.
GPS and Chart Plotter Terminology
The terminology and acronyms used can be very confusing. See my GPS terminology explained page for definitions and acronym.
What's a GPS and
What's a Chartplotter?
Global Positioning System, is a satellite based navigation system. It provides position as long as there is unobstucted line of sight to at least 4 GPS satellites. GPS is maintained by the US Government. Other countries are developing their own systems GLOSNASS is the Russian System, Galileo Positioning System will be the European system and the Chinese are developing the Compas Navigation system. The Indian system is also in the works.
A GPS unit does not necessarily show chart positions although some will show a map and your position on the map. Properly speaking when a GPS shows position on a chart it is a Chart Plotter. The 2 terms seem to be used loosely. Some people will refer to gps and gps charts. A chartplotter always displays charts.
GPS and Chartplotters will give you position in longitude and latitude. This information can be passed on to other marine instruments such as radio equipped with DSC (Digital Selective Calling).
Some features of GPS/Chartplotters
If you are willing to pay the big bucks, what can you get?
- The larger the display, the pricier the unit. Garmin has a 15inch unit for 7000 US (2013)
- Touch screen is available for higher end units.
- System integration, that is the ability of the chartplotter gps to talk to other instruments on board. Some of these instruments are Radar, sonar, weather, other boat tracking, ship network.
- Lots of money buys you lots of map redraw speed.
- Memory and computer connectivity are also on a sliding scale of cost.
- In the higher end models the chartplotter starts to behave like a computer and allows you to control music, video and whatever other things are on board.
A few steps down
Most of us are in the not wealthy category and there are a large number of units that are offered in the low to middle range.
- All GPS will tell you where you are and your direction of travel. They will also let you know how fast you are moving over ground. SOG is speed over ground.
- Most will have a compass of sorts. Some quite elaborate.
- Most GPS will be waterproof within limits. Most can certainly take splashing if their ports and covers are properly in place.
In some very basic units or older models, that's it. There could be a map underlay but most do not have them.
Less Basic GPSs
- Will allow you to set waypoints
- Will track your trip so that when you look at where you've been there is a whole lot of little spots or triangles showing how you have meandered.
- Will allows you to program in Routes. So you know how to get to various spots.
- More money=more routes, more waypoints and more little triangles. Also more flexibility in setting these up.
- As you get more elaborate units the interconnectivity increases. NMEA 0183, NMEA 2000 are data transmission protocols that many instruments in the marine world use. These instruments could be commonly sonar, radar, and various monitoring devices such as fuel, temperature, or AIS which tracks the ID and whereabouts of big boats and passenger vessels.
- A common add on to Chartplotters is sonar. It gets marketed as fishfinder but shows water depth, bottom type and of course fish. If Sonar is supported you are expected to buy and install a transponder 100-200 dollars. It transmits a pulse and receives an echo. Many transponders need to be installed through the hull, but some can be installed over the transom, or inside the hull against the fiberglass or metal (as long as it is not a mushy core inside the wall.)
- Transponders can be single or double frequency. Double increases accuracy.
- WAAS is Wide Area Augmentation Systems which provide for better accuracy in Most of Canada, Mexico, and Alaska, and all the continental US. It is not available elsewhere. It's a system that measures deviation in GPS and sends in corrections if an error is found. (I have more details on my gps terminology page.)
People I asked who had WAAS did not feel that it made much of a difference to a regular civilian boat. In Europe EGNOS provides this function, in Japan augmentatin is provided by MSAS.
- Many alarms are designed into the units. You can set Route Deviation Alarms, Anchoring drift alarms that tell you if you have moved beyond the expected swing of your anchor, depth alarms if you have a sonar feature, Fish alarms.
- Most chartplotters will come with a basic map and you are expected to buy a local package. Not all maps and charts are recognized officially. If the chart is approved by ECDIS, then it can legally replace paper charts. (Its a good idea to keep the paper charts to get the big picture, or to have as a backup if your battery goes flat.)
- Charts can be entered into a chartplotter several ways. Some units support all or only one. Some will connect to a computer and have internal memory to store map / chart information, many do not have internal memory and rely on small SD cards to provide memory. Other units have the charts preloaded at the shop.
- Depending on the connections your unit has, it may be able to send out distress signals. IF you have a VHF with DSC connected to your unit some Chartplotters will send out signals.
- A connection is to weather information. A chartplotter can sometimes be interfaced to receive detailed weather reports. This is a paid subscription to XM WX in Canada and the US
- Tide and moon phases tables are sometimes offered.
- Most units will be waterproof. Some will float but not many. Some hand held units do.
- Handheld GPS units will sometimes have straps and clips that allow you to place them on your wrist, or attach them to your clothe or PDF.
- At this point the that's about the limit in features. Not many handheld gps will be more expensive than 350, and many are much less. AS I looked at the different units the features were much the same and 400 or less dollars got you a pretty complete range of features including sonar/fishfinder.
- All Chartplotters that I have seen depend on an external battery. All handheld units have internal batteries.
- More money often gets you longer battery life, or lighter weight in handheld units.
- If you want to add more money you can get larger, better screens, and increasing connectivity with your other toys. There are not many touchscreens because they don't work very well when they are wet.
How to decide what GPS to get?
Make a list of what you expect your unit to do. Remember that the day after you buy your GPS is the day a newer better model comes out, so don't fret.
Here is a link to a Garmin GPS search in Amazon.com.
Garmin Marine GPS
First have a look at my page of acronyms and vocabulary, it makes it easier to understand descriptions and features if you know the vocabulary.
Some questions to answer in choosing a GPS will be:
- Handheld or Mounted?
- Dinghy or Keelboat?
- Self-contained battery or ship's battery?
- Detailed Charts vs GPS information only?
- Anchor alarm?
- Depth alarm?
- WI-FI enabled?
- Are the charts included or do you have to buy them extra for chartplotters.
- Lots of routes or waypoints such as racing marks?
- Connected to other instruments such as VHF? or Radar?
- Would you prefer to soup up your iphone or tablet with GPS aps. See the Right hand Box for links. They are not waterproof and battery life is limited but it can be done. This is only possible if you have service in the area.
I've included a couple of links on the side bar that offers this.
email me : Christine