A GPS receiver can be a stand-alone handheld unit, a car navigation unit or a module for use with a Palmtop or PC.

The most common receiver type is the 12 parallel channel receiver which can collect data from up to 12 satellites at one time.

What interface can be used to transmit data from your computer. Most common are serial and USB.

Filtering on "Yes" will show all products available with either IPX-7 or IPX-8 waterproof specifcations. The available standards are the following:

IPX-0 No special protection

IPX-1 Protected against falling water Equivalent to 3-5mm rainfall per minute for a duration of 10 minutes. Unit is placed in its normal operating position.

IPX-2 Protected against falling water when tilted up to 15 degrees - Same as IPX-1 but unit is tested in 4 fixed positions - tilted 15 degrees in each direction from normal operating position.

IPX-3 Protected against spraying water - Water spraying up to 60 degrees from vertical at 10 liters/min at a pressure of 80-100kN/m2 for 5 min.

IPX-4 Protected against splashing water - Same as IPX-3 but water is sprayed at all angles.

IPX-5 Protected against water jets - Water projected at all angles through a 6.3mm nozzle at a flow rate of 12.5 liters/min at a pressure of 30kN/m2 for 3 minutes from a distance of 3 meters.

IPX-6 Protected against heavy seas - Water projected at all angles through a 12.5mm nozzle at a flow rate of 100 liters/min at a pressure of 100kN/m2 for 3 minutes from a distance of 3 meters.

IPX-7 Protected against water immersion - Immersion for 30 minutes at a depth of 1 meter.

IPX-8 Protected against water submersion - The equipment is suitable for continual submersion in water under conditions which are identified by the manufacturer.

After the US military stopped the random errors inserted into the GPS system, most receivers now have an accuracy of 15 meters or better 95 % of the time. To get the best accuracy, the GPS receiver needs a clear view of the sky. Reflections from tall buildings can change the time for the signal to reach the receiver, therefore giving an error in positioning.

This is the time from when you turn on your GPS unit until it has received signals from a sufficient number of satellites and calculate its first position. If the unit has been turned off for a long time (4-6 hours), its satellite almanac (a list of where the satellites are supposed to be at a certain time) will need updating and the first fixed location will therefore take longer (cold acquisition).

This is the time from when you turn on your GPS unit until it has received signals from a sufficient number of satellites and calculate its first position. If the GPS unit has recently been used, the first fixed location will be quite fast.