Garmin's MapSource documentation is scant.

Maritime navigation aids aren't covered at all in the help, and if one isn't versed in the standard abbreviations, they're quite difficult to understand.  There are several types of navaids included -- I'll try to cover all of the ones I've found.  If you know of any major ones that I've not covered, please do let me know so I can add them.

• Color -- Navigational aids appear as black dots with an white letter in the center.  The letter indicates the color of the navaid.  In cases where a navaid has multiple colors, the icon is half black/half white.  This is something that Lowrance has done a handled differently.  Their icons clearly indicate the type of navigational aid, but not the color.  I think the Lowrance icons are prettier, but contain less information.  You should check out their U. S. Navigation Aids Page for a comparison.  The MapSource CDs have different icons for each of these major navaid types so maybe a future device from Garmin will handle them differently.  Here are the major colors:
  • G/Green -- Found on port (left) side aids as returning from sea and mark the port side of the channel or an obstruction.  These aids are odd numbered, but that information is not available on the GPS.
  • R/Red -- Found on the starboard (right) side aids as returning from sea and mark the starboard side of the channel or a hazard.  These aids are even number, but again, that information is not included on MapSource.
  • R-G/Red-Green -- Marks junctions in the channel or hazard that can be passed from either side.
  • R-W/Red-White -- Marks mid-channel or divides a channel into "in" and "out" lanes.  If this is a lighted navaid, it will simply be White.
  • Y/Yellow -- Represents all special-purpose navaids that don't have lateral significance, i.e., from or to seaward.
• Type -- At some zoom levels, the display will show the description automatically, but you can always move the map pointer over the navaid to display its description.
  • Lights -- These are the most common navaids in the database.  They begin with a code that describes how the light blinks.  It's followed by the color and the frequency of the blink.  There are many types of lights:
    • F/Fixed -- A continuous, steady light.
    • FL/Flashing -- The most common light in the database.  A single flash at regular intervals, the duration of light always being less than the duration of darkness.  These lights are warning mariners of shoals surrounding Fort Jefferson in the Dry Tortugas National Park.
    • Q/Quick Flashing -- Flashes at least sixty times a minute and is used where special piloting attention is needed.  In addition to a flashing white over six seconds, there are two more complex flashing lights:  A group flashing three greens over twelve seconds and a alternating flashing white/red over three seconds.  This nice selection is at Istanbul, Turkey.
    • OC/Occulting -- This light is on more than it's off.  This example from Mumbai (Bombay), India and there are two.  On is red with a five second interval and the other alternates betwen red and white with a five second interval.  You can also see a fixed red light and a quick flashing white light.
    • ISO/Isophase -- Periods of light and darkness are equal.  This example in Havana, Cuba is yellow.  Also here is a flashing green and a group flashing two whites followed by a longer period of darkness over fifteen seconds.
    • MO/Morse -- A very rare light, I think.  It flashes out the letter indicated in the description.  The example here is from the mouth of the Suez Canal, Egypt.  It flashes the letter "U" in white over a fifteen second interval.  Also described are a fixed white, occulting red, and two flashing whites, one at three second and the other at five second intervals.
  • Daybeacons -- Generally specially shaped signs mounted on piles.  They substiture for buoys.  Only four kinds and the color is almost always associated with the shape:
    • SG/Square-Green -- MapSource will follow with a statement telling how the navaid is mounted.  This shot is taken in the Dry Tortugas National Park, right at the end of the Florida Keys.
    • TR/Triangle-Red -- As you can see on the graphic, there are two examples described as "TR ON PILE". 
    • Octagon -- There should be an octagonal daybeacon, but I have not found an example of it on the map.  If they do exist, they should be marked Red-White.  If you know where one's located, please let me know so I can add it.
    • N/Diamond -- Finally, there are diamond shaped navaids that is frequently used to mark a hazard, but it can also be used to make a minor light that's not part of a channel.  They should be yellow, but the example I found in the keys is white.  MapSource follows the designator with how it's mounted and then some additional information.  In the Keys example, it says "NW ON PILE WORDED DANGER CHANNEL CLOSED".
  • Unlighted Buoys -- They will have the same icon as the other navaids, but the color and name will be spelled out.  Should only be two:
    • Green Can -- In both cases, the color is indicated by the icon.  The shape of the buoy also indicates the color.  Cans are green....
    • Red Nun -- and nuns are red!
• Other -- A very few items are not color coded and have different icons.  These items do not appear to be part of the marine database and they do not display zoomed out as far as the icons we've already discussed. 
  • Radio Beacons -- Operate similarly to Morse lights -- they transmit a radio signal with the letter indicated, in this case "T".
  • Bell -- This example is in the Delaware River just upstream from Fort Delaware State Park.  I can't tell what the icon represents, but the message is self explanatory:  One ring of the bell every twenty seconds.
  • Marker -- I have no idea why this shows up as a square, as I would have thought that it would match up with one of the standard types.  The full text of the message is "SPECIAL WARNING MARKER PPA ON SUBMERGED DIKE".  If you can shed light on this one, please let me know.
  • Horn -- Horns are also represented by squares and the legend is clear:  One blast every ten seconds for one second.  This is a little further up the Delaware River, just past the Philadelphia Airport.

Bibliography

If you would like to find out more about the books, videos and CDs that I reference on these pages, you can do so here through an arrangement we have with Amazon.com.  These references will take you to Amazon.com's stacks and you can find out more about the source of the book, video or CD, reviews from readers, viewers & listeners as well as availability and links to other books, videos or CDs with similar titles, subjects and authors.  You can also leave your comments on each of the works!

• Chapman Piloting -- Seamanship & Small Boat Handling, Elbert S. Maloney & Charles Frederic Chapman, 1996.
  An excellent reference on everything boating.  I refreshed by rusty memory by referring to the "Aids to Navigation" chapter.