Terminology

Below are the Definitions of everything you need to know about a GPS from "Barometric Altimeter" to "WAAS Enabled"

Barometric Altimeter – If the unit says that it has a “barometric altimeter”, this will give extremely accurate elevation data based upon the atmospheric pressure.  Beware, however, that as with any atmospheric pressure dependant device, the accuracy of a barometric altimeter depends upon the weather conditions at the time, specifically the barometric pressure, which at sea level on a “standard day” is 29.92” of mercury. 

Many GPS units allow you to enter the current barometric pressure, if you happen to have that information, for a much more accurate reading.  Many of the cheaper GPS units will display GEOMETRIC altitude information that’s based upon and calculated from the x-y (horizontal positions) and z (vertical position) coordinates as received from the GPS satellites and usually will not be as accurate as atmospheric pressure measurements.  Included in this inaccuracy is that the vertical accuracy of GPS is about 10 times less accurate than its horizontal accuracy and further degrades if the signal quality is low. 

Disclaimer:  Altitude measurements based upon the barometric pressure of the atmosphere is, at best, a relative thing and is only as good as the last known good barometric pressure adjustment entered into your GPS unit.  But for most people the altitude measurements that they provide are perfectly adequate. 

DCS or CTCSS – GMRS and FRS radios have Digital Controlled Squelch (DCS) or Continuous Tone Coded Squelch System (CTCSS). If you are not transmitting the squelch code used by the other radio, the person at that radio cannot hear you. They would first have to disable the squelch control.

Electronic Compass – If the unit says that it has an “electronic compass”, this means that it displays an accurate heading even while standing still.  While many of the cheaper GPS units will have a compass function, it won’t operate properly unless you are moving. 

FRS – Family Radio Service is the frequency bandwidth available in North America for short range two-way radio communications. FRS radios can usually communicate over a distance of 2 miles in line of sight. FRS radios let users communicate by pressing a “talk” button, speaking, then releasing it to wait for a reply from another user. FRS two way radios are meant for free communications during leisure activities such as a walk in a park or a visit to a shopping center. There are 14 channels available, 7 of which are low power, FRS Only channels, channels 8 - 14.  Channels 1 – 7 are GMRS/FRS shared channels.  The power level is limited to 0.5W. GMRS and FRS frequencies are located in the 462 and 467 MHz bands of the UHF spectrum.  No license is required for FRS radio operations. 

FRS/GMRS – Recently, hybrid FRS/GMRS consumer radios have been introduced with 22 channels, instead of the 14 channels associated with FRS. On this type of radio, channels 8-14 are strictly license-free FRS channels. Transmitting on all channels above channel 14 requires a license. Transmitting on the shared FRS/GMRS channels 1-7 requires a license, if using more than ½-watt. It is the responsibility of the radio user to read and understand all applicable rules and regulations regarding GMRS.

Geocaching – Geocaching is an outdoor activity in which the participants use a GPS receiver to hide and seek containers, called "geocaches" or "caches", anywhere in the world.  A typical cache is a small waterproof container containing a logbook. Larger containers such as plastic storage containers (tupperware or similar) or ammo boxes can also contain items for trading, usually toys or trinkets of little value. Geocaching is most often described as a "game of high-tech hide and seek," sharing many aspects with benchmarking, trigpointing, orienteering, treasure-hunting, Letterboxing, and waymarking.  Numerous websites list geocaches around the world.

GMRS – General Mobile Radio Service.  GMRSs are intended to be used by families communicating inside their neighborhood or during recreational activities.  The power level is limited to 5W for a distance of up to 14 miles, line of sight. GMRS and FRS frequencies are located in the 462 and 467 MHz bands of the UHF spectrum.  An $80 license/permit, good for 5 years, is required to operate a radio in GMRS frequencies at GMRS power ranges. 

IPX7 – The designation IPX7 is actually IEC Standard 60529 IPX7 which states that a device with this rating can withstand immersion in 1 meter of water for 30 minutes.  Prolonged submersion can cause damage to the unit.  After submersion, be certain to wipe and air dry the unit before reuse or charging. 

SiRF, SiRFstarIII, and SiRF Star III – Just like PC’s use various recognized “chipsets” such as Intel or PowerPC, regardless of who manufacturers the PC, the GPS industry also uses particular chipsets as the core of their GPS units.  SiRF a CSR plc company, formerly SiRF Technology Holdings, Inc., has developed a chipset that has much greater sensitivity, more channels (up to 20) to receive more satellites, and massively parallel correlators.  It is the correlators that give it the capability of receiving very weak signals.  This technology also improves on multi-path reception where the receiver sees more than one signal due to signals being bounced off of nearby objects or structures. 

The bottom line is that GPS units with this type of chipset will be able to acquire a “fix” (know its position) faster and be able to hold onto it even in deep canyons, dense forests, cloud cover, and dense cities better than those that use the older technologies (more than 5 years old). 

However, just because Intel and PowerPC have the lead on chipsets for PC’s, this doesn’t mean that there aren’t other competitive and viable chipsets being made out there.  The same goes for GPS chipsets.  With all the competition today, particularly with the SiRF chipsets on the market, other chipset manufacturers have also come out with viable chipsets, meaning that just because a GPS doesn’t say that it uses the SiRF or SiRFstarIII chipset, doesn’t necessarily mean that it won’t work just as well as those that do. 

WAAS Enabled – This stands for Wide Area Augmentation System but what it means for you and me is that you get better positional accuracy than those that are not WAAS Enabled.  It used to be that you couldn’t get a WAAS Enabled GPS receiver unless you were connected in some way with the military and given the codes required to turn off Selective Availability (SA) which deliberately degraded the signal, therefore the accuracy on non-military GPS receivers prior to May 2, 2000.  But now most all GPS receivers are WAAS Enabled.  Non-WAAS enabled receivers have a horizontal accuracy of around 7 meters while WAAS enabled receivers have a horizontal accuracy of around 1 meter.