GPS Navigation - Finding Your Way Through the Product Maze

The range of options and variety of brands and models can make choosing a GPS system a little confusing. Price is an obvious consideration but so are the built in features and available options, how and where you intend to use your GPS and what kind of directional assistance would be most helpful for your particular needs. When deciding which GPS product is right for you, considering the answers to some of the following questions will help you navigate through the maze of available products and find the right one for your needs.

- Are you looking for basic GPS navigation for you car to help get you around town or something with a few more features that would be helpful on trips?

- Are you looking for a GPS system with more versatility? Perhaps a unit that could be used in a car and/or outdoors hiking, biking or sightseeing?

- Are you looking for a feature packed system that provides spoken navigation and a variety of additional information, traffic and weather, compatibility with Bluetooth devices XM radio and more?

- Are you looking for activity specific GPS capabilities for use during hunting, fishing/marine use, or fitness training?

The following information is offered as a guide to assist you in determining which product is right for you. It is not a review of any specific brand or model. The brands mentioned are only used as examples of the kind of GPS being discussed. Keep in mind as you consider your needs that many GPS systems designed for use in a car can easily be carried in a pocket, purse or pack and used to navigate on foot. And likewise, many handheld products can be mounted in a car, boat, ATV or on a bicycle and when installed with street map software, can be used to navigate on streets and highways.

GPS products with basic capabilities will be able, literally, to get you from point A to point B by utilizing one or more saved "Way points". These type devices do not offer mapping capability. You can think of way points as pebbles left behind you as you make your way. To return, you move back along your route, collecting the pebbles you left to mark the way. Basic models function in much this way, dropping the "pebbles" for you and pointing the way back to them to lead you home. Examples for use of this type GPS might be saving the location of your parked car at a crowded shopping mall or sports facility when you arrive so you could easily find your way back when you are ready to leave. Or instead of a parked car you might save the location of your campsite and points of interest along a hike and then easily navigate back at the end of the day. Examples of these types of handheld GPS units would include:

- Bushnell's Backtracker Personal Location Finder

- Garmin eTrex H

- Garmin Foretrex 101 and 201

- Geko 201

- Garmin GPS 60, 72, and 76

Basic automobile GPS navigation requires a bit more sophistication than seen in the previously mentioned handhelds. These products offer pre-loaded maps, color screens, and greater memory capacity and are the types of products you would want to consider for use in a vehicle or for back country hiking, hunting or fishing. Beginning level examples of these products would be:

- Garmin Nuvi 200, 205, 205W

- Magellan Roadmate 1200, 1400,

- Magellan Maestro 3200 series

Moving up a notch consider products like the following handheld units for outdoor activities :

- Garmin eTrex Legend, Venture HC, Vista,

- Garmin GPSMAP 60

- Magellan Triton 200

Moving up to the mid-level you may want to consider products like these for your car:

- Garmin Nuvi 250, 255, 260, 265, 270 series

- Magellan 1412

- Navigon 2000S

And for outdoor handhelds:

- Garmin eTrex Summit HC, Vista HCx, GPSMAP 76S

- Bushnell ONIX200

- Magellan Triton 300

- DeLorme PN-20

Moving up to more advanced products does not mean struggling with products that are difficult to use. Features such as touch screens and spoken turn by turn directions make these automobile GPS products very easy to use. Advanced products provide a greater number of features and a higher level of functionality and versatility. Options such as XM radio, Traffic updates, or other services are included or can be added with some of the more advanced models. Some of these options require the purchase of monthly subscriptions. Examples of these products for your vehicle would be:

- Garmin Nuvi 265WT, 275T, 500, 550, 750, 755T, 760, 765T, 775T, 780, 785T, 855

885T, 5000

- Garmin Zumo 550

- Garmin Streetpilot 7200

- Magellan Maestro series

- Navigon 2200T, 2100MAX, 7200T, 8100T

Advanced handheld GPS models generally offer more internal memory or the ability to add mapping and other content using data storage cards. Mapping data can be downloaded to the card and the card plugged into the device. In this way one device can be used to navigate city streets, inland lakes or coastal areas, or trails in a national park depending on the mapping software installed. These types of handhelds include:

- Garmin Oregon and Colorado series

- Garmin GPSMAP 60Cx, 60CSx, 76Cx, 76 CSx

- Magellan Triton 1500, 2000

- Bushnell ONIX350, ONIX400

- DeLorme PN-40

There is a group of advanced products which should be mentioned separately because they not only offer excellent automobile navigation features but can be used for marine GPS navigation on the water or on a trail as well. These GPS models are referred to as crossover or hybrid GPS units and include the following examples:

- Garmin Nuvi 500, 550

- Garmin GPSMAP 276C, 478C, 620, 640

- Lowrance XOG

Another group of handheld GPS is designed with a specific use or feature in mind. Some specialized handheld models provide basic GPS navigation but are also coupled with enhanced specialized functionality. Others do not offer GPS navigation but use GPS technology to gather data used in activities such as fitness or sports training. Examples include:

- Garmin Astro - Handheld GPS that can also be used to track hunting dogs.

- Garmin Rino - Handheld GPS with 2-way radio capability.

- Timex Ironman - GPS worn on the wrist. Tracks such things as time and distance for running, biking, and swimming fitness training.

- Garmin Edge, Forerunner, and Foretrex - Edge is a Personal Training/Biking calculator using GPS for fitness training. Forerunner and Foretrex are other examples of wrist mounted GPS, Forerunner for fitness training and Foretrex offering basic way point GPS navigation.

This has not been an all encompassing discussion of GPS products but I hope this information will help you understand the differences between some of the more popular models when choosing which is the right GPS for you.

By James E McMillan

NTP Server Static GPS Antenna Systems

The Global positioning System (GPS) is often used by computer equipment, such as NTP Server systems, to provide an accurate timing reference for time critical applications. This article provides an overview of GPS for timing applications and describes the equipment used to install a GPS antenna in a static location.

Overview - Using GPS for Accurate Time

The Global Positioning System is a US military system for worldwide navigation. The system consists of 24 orbiting satellites, each satellite has a highly accurate atomic clock on-board synchronised to UTC time. The satellites continuously broadcast time and position information. The time and position information can be obtained worldwide with a GPS receiver and antenna. GPS works continuously in any whether conditions, anywhere in the world. Additionally, there is no set up fee or subscription charges to utilise the GPS systems. Many computer timing systems and NTP Server systems utilise GPS as an accurate external timing reference.

The Accuracy of GPS Timing Systems

GPS receivers provide highly accurate position and timing information. Typically, a GPS receiver can provide positioning information to an accuracy of 15m. NTP Server systems can obtain timing information from GPS to a resolution of a few nanoseconds.

The GPS Signal

The transmitted GPS signal is very weak low-power radio signal, designated L1 and L2. L1 is the civilian GPS frequency transmitted at 1575.42 MHz. The signals travel by line of sight and can pass through clouds, glass and plastics but are blocked by objects such as metal and brickwork. Therefore, the ideal location for a GPS antenna is on rooftop with a full 360-degree view of the sky. However, often installation on the side of a building or in a window can provide adequate results. As a rule of thumb, the better the view of the sky, the greater the likelihood of a good consistent signal lock.

GPS Timing Antenna Types

The GPS antenna acts as an amplifier to boost the GPS signal for transmission along a cable, usually coax, to the GPS receiver. GPS Timing antenna's provided with NTP server systems utilise a pole-mounting system. The antenna screws to a threaded pole for installation on rooftops. This arrangement provides the GPS antenna with a rigid mount easily able to withstand high winds without damage. Typically the GPS antenna is fairly small in size, measuring less than 90cm in diameter. Low-cost patch type antennas are also available, but these are generally better suited to vehicle applications.

GPS Antenna Cable Types and Cabling Distances

The cable distance that can be utilised by a GPS antenna depends mainly on the amplification of the GPS antenna and the quality of coax used in the installation. A typical GPS timing antenna may have a gain of 35 db. Relatively low-quality coax such as RG58 has an attenuation of 0.64 db/m at 1575 MHz. Therefore, a cable run of 55m can be obtained using RG58 cable. With very high quality coax cable, such as LMR400, an unaided cable run of 200m can be achieved. However, very high quality coax can be expensive. A good price-performance compromise is LMR200 cable, which can be run unaided to 80m.

Extending Cabling Distance with In-Line GPS Amplifiers

In-line GPS amplifiers provide further amplification of the GPS signal to increase the cable distance between the GPS antenna and receiver. GPS amplifiers are fitted in-line with the antenna cable and obtain power from the receiver via the coax cable. No external power-supplies are required. Typically, a GPS amplifier may add a further 20 dB of gain, adding 30m of low-quality RG58 coax, 40m of LMR200 coax or 100m of high quality LMR400 coax. Additionally, multiple in-line amplifiers may be utilised to further increase cable distance.

Sharing a Single Antenna Between Multiple Receivers - GPS Splitters

GPS splitters allow a single GPS antenna to be utilised by two or more NTP server systems. The GPS splitter splits the signal received from the GPS antenna into multiple outputs for synchronizing multiple NTP servers. GPS splitters are generally available with 2, 4 or 8 outputs.

Protecting GPS Systems - GPS Surge Suppressors

Surge suppressors protect expensive NTP server equipment from electro-static discharges, such as lightning, that may be picked up by an externally mounted GPS antenna. Surge suppressors are installed in-line on the coax cable between the antenna and receiver, ideally where the cable enters the building. Surge suppressors require a low-impedance ground, to discharge any received surge. The surge suppressor requires no power-supply or additional cabling.

By Dave Evans