You will be plugging the appropriate serial cable into a serial port on your computer.  You may have more than one hardware serial port, which usually consists of a DB9 connector - 9 pins in two rows, one row of 5 and one row of 4. You need to figure out which logical port it is from the computer's point of view - COM1, COM2, COM3, and so on.  Make sure no other program is configured to use that port.  This could be a mouse driver, modem driver, network driver, handheld hotsync program, IrDA port (infrared port), etc.  For Windows check the Settings/Control Panel and be careful you don't turn something off (disable) that you don't really want to turn off.

The National Marine Electronics Association (NMEA) issues standards for interfacing marine electronics devices.  GPS receivers can be one of those electronic devices that support NMEA protocols.  When the GPS receiver is set to NMEA, it usually sends a "steady stream" of current position data to whatever is listening.  This is often used for real time tracking on a laptop computer running a mapping program.

If you are having trouble getting your GPS receiver to communicate with your computer program that supports GPSRs try setting the GPS receiver to NMEA mode (serial data format).  When the receiver has a lock or is in simulator mode, it should send out NMEA data strings (ASCII text) which you should be able to see with a terminal program (i.e. HyperTerminal with Windows) on the computer.  The default speed is usually 4800 bps on the GPS receiver so make sure that the terminal program is set to the same speed.  If you receive the NMEA strings then you know you have the correct port and the cable is good for sending data in at least one direction.  It doesn't necessarily mean sending data from the computer (handheld) to the GPS receiver will work.

The GPS receiver does not know what is in between you and your destination.  When it gives you a line pointing to your destination that doesn't mean you can walk the straight line to it.  There may be all sorts of obstacles in the way.  I hope this is obvious!

This is partially true of maps. A map may show you some obstacles but not others.  For instance an impassable cliff may not be noticeable on a topographic map.  A cliff may be smaller than the contour interval of the map and hence, may not be noticeable.  Also a bog/swamp may not be shown on the map, there may be a beaver pond where there wasn't one before, and vegetation may be too thick to get through easily or at all.

Use routes or draw your own track log(s) to show you where to travel to get around obstacles.  You can create these on a computer with appropriate background maps and any other materials you can obtain ahead of time such as guidebooks.  Of course, expect that you didn't find out about all the obstacles so you may not be able to follow your "trail track log" exactly.

In some cases battery (power) save mode consists of shutting down the receiver (not the whole unit) and only waking up every few seconds to get a fix.  If you are in a difficult reception area it will take some time to get a fix and the receiver will end up running most of the time thus consuming power for little or no savings.  In addition the receiver will perform poorly since it doesn't have a fix most of the time.  Out on the open road battery save mode can work well but then I'm running off the car's power, so I don't care.  I never use battery save mode while hiking or any other time.

So your actual run time may very well be less than the manufacturers specification. 

• Mark the location of your parked vehicle or the location of your camp!

• Reset (clear) the track log if you didn't store a predetermined log as a trail map to follow or a track log for boundary information (coastline, private property, country, etc.).

• Check the track logging settings: On/Off, Interval, etc.  With Garmin receivers when you get to your destination you can save the track log and do a "TracBack®".   Then the receiver can give you information about your return trip. Some Magellan models can back track the recorded log.

• Reset the trip odometers, time, averages, maximum speed, etc.   Don't reset the waypoints or routes.  You preloaded the receiver with this information for your trip - right?

• Let the receiver run with good view of the sky for around 5 to 15 minutes.  Use the longer time if the receiver hasn't been used for awhile so it can get current satellite almanacs.  Do this if you are interested in the best accuracy.  Otherwise you might just wait until the receiver is using the obvious set of satellites. If you are about to enter a forested area, it is especially important to wait until the receiver has picked up the satellites that are in view.

• If you have a receiver with a barometric altimeter, you might want to calibrate the altimeter to either the known elevation or the GPS elevation.  This might be done even if you have an auto calibration function turned on because the GPS elevation or actual elevation may be a bit different from the initial barometric elevation and it may take awhile before the auto calibration brings the barometric elevation into sync with the GPS elevation.

The Garmin receivers do not really have a save track function although that is what it is called.  The operation is a reduce and then store function.  It is used for a detailed back track route that Garmin calls "TracBack®".  It only stores the most significant points of your route (up to 250 points on most current models and is being increased to 750 in some new firmware releases).  These track storage areas are good for storing trail maps, coast lines, boundary lines, etc.  You can create the line set on the computer (but not necessarily with MapSource) and send them to the receivers storage areas.  Besides the horizontal coordinates the elevation, time, and date are recorded in the track log.  The times and dates are removed when a "save" is done.  There are exceptions.

With Garmin receivers, you do not need to "save" the active log to transfer it to a computer.  The active log and all the stored logs in the Garmin receivers are transferred to the computer when a track log transfer is done.  For more on Garmin models see:  Primarily Garmin Tips, Hints......

Lowrance's name for track logs is "trails" or "plot trails".  The Lowrance iFinder can save up to 10 trails of 9,999 points in the iFinder's memory and additionally save this data to MultiMedia Cards (MMC) or Secure Digital (SD) Cards.  I understand that "10" trails is not a fixed limit.  You might be able to save say 20 trails of 4,999 points (can't exceed a maximum 99,999 points).  The iFinder has "Auto", Time, and Distance logging options and it has a "navigate a trail" function.

Magellan Meridian series holds about 2,000 track points and can store the track in an SD card. The Meridian has Fixed Rate, "Auto", and "Auto Detailed" track logging options and can navigate a back track route created from a track log.

The Magellan SporTrak series holds about 2,000 track points and doesn't have SD card support.  It has a save track to route function.

A water "splash" can exceed a GPSR's "waterproofness".  A wave (splash) hitting the GPSR while riding some rapids can exceed the pressure exerted by one meter of water.  There's a difference between a static, submerged water specification and a dynamic one.  Hydrodynamic pressure during a splash can be greater than the hydrostatic pressure of IPX7 specifications.  A water damaged GPSR that was splashed won't necessarily be covered by the manufacturer's warranty.

Some commercial cables that are made to connect a PDA to a GPSR will not work with some combinations of PDA's and GPSR's that you might think would work based on the description of the cable.  For instance I bought a cable to connect the Sony CLIÉ T/NR series PDAs to Garmin receivers.  It worked when an SL10 was connected to a Venture or a GPSmap 76 but not when the SL10 was connected to a GPS 76 or a 12XL.  Looking at the signal levels, I would say it was very marginal when used with the Venture and GPSmap 76.  That might be why the GPSmap 76 worked and the GPS 76 didn't.

What's this about supplying power to a cable?  Isn't a cable just wire?

Some PDA's (especially new ones) input/output the serial data at the PDA's internal logic levels.  They expect the cable to provide the circuitry to change these logic levels to RS232 logic levels.  Just about everyone (with regard to the devices discussed here) takes some sort of shortcut in implementing the handling of RS232 logic levels.  This has created a nightmare with regards to getting things to work together.

For additional information (especially connecting a Sony Clie SL10 to a Garmin GPS receiver) including a wiring diagram:

"Connecting a PDA to a GPS Receiver"

(Idea from posting by Richard Mitchell on sci.geo.satellite-nav newsgroup)

The FAA leases to use the satellites listed above expire in July 2007.
AOR-W (PRN 122, NMEA 35) and POR (PRN 134, NMEA 47) are to stop sending WAAS signals on July 30, 2007.

WAAS uses a system of ground stations to provide tracking data to master stations on the U.S. East and West coasts.  The master stations compute a set of correction data for the U.S. that is sent to the satellites for re-transmission to GPS receivers.  If you are more than about 500 miles from a ground station, the correction data is probably invalid.  So if you are in Central America, you can receive the data from the WAAS satellites but the correction information is not applicable to that area.  You should disable WAAS in your GPS receiver when you're not in a coverage area or when you can't get reliable WAAS signal reception.

In Garmin receivers the letter "D" is put in the satellite strength bar (or above if the bar is short) when WAAS correction data is being applied to the signal from that GPS satellite.  When WAAS is enabled the satellites that don't have a "D" are not being used in the position computation (but could be different on newer receivers/models).  So you can get a "2D Differential" location indication with solid indications on eight satellites but with only three satellites receiving differential corrections.  Hopefully this will change in a future firmware release.  Disabling WAAS will cause the use of all eight satellites and probably a "3D GPS Location" fix.

Other countries are developing satellite-based differential GPS systems.  The Japanese are implementing the Multi-Functional Satellite Augmentation System (MSAS).  And Europe is creating the Euro Geostationary Navigation Overlay Service (EGNOS).  It may be usable (non-critical applications) in the summer of 2003.  Note:  As of May 2006, people have been receiving EGNOS (ESTB) test signals but it isn't fully operational yet.
 

The standard formats for specifying longitude are: DDD.DDDD, DDDMM.MMM, and DDDMMSS.SS
East (E) is positive (+) and West (W) is negative (-).
Leading zeros are required in both cases.

For example 5 deg 7 min 42.06 seconds N and 31 deg 45' 7.19" W becomes
+050742.06-0314507.19
 ddmmss.ss dddmmss.ss

An additional number appended to the above would be the altitude in meters and the string may end with a "/".

The United States Coast Guard uses the form "DDDMM.MMM" (degrees, minutes, decimal minutes) for a common standard.

TIP: If you have a Garmin 76 series GPS receiver and the location format is set to something other than degrees/minutes, you can change the location display on the satellite page to degrees/minutes by pushing the rocker key up or down.  Pushing the rocker key up or down again will change it back.

There are 60 minutes in one degree and there are 60 seconds in one minute.  Latitude runs from 0 degrees at the Equator to 90 deg. at the poles.  It is 0 to 360 deg. around the Earth with 0 (and 360) deg. being the Prime Meridian that goes through Greenwich (pronounced gren'ich), England.  Normally numbers greater than 180 degrees are not used.  Instead positive numbers up to 180 deg. are used going east from the Prime Meridian and negative numbers are used when going west.  Note that "37.87" can't be deg.minutes since "87" can't be minutes - sometimes the "decimal" point is put in the wrong place and/or used as a separator instead of as a decimal point.  Note that comma and decimal point usage is different in Europe and the U.S.