A number of GPS receivers are on the market. Usually a GPS receiver with more features costs more.

GPS manufacturers have done a pretty good job making user interfaces easy to use. After you know the basic concepts of GPS receivers and are familiar with a manufacturer’s user interface, a GPS Tracking Device is usually as easy to use as a cellphone and easier to use than a personal computer.

Display and output

GPS receivers have three choices for information display or data output:

   Monochrome LCD screen: Most GPS receivers have a monochrome liquid crystal display (LCD) screen.

Color screen: These are especially useful for displaying maps.

Color screens usually have shorter battery lives than monochrome ones.

   No screen: Some GPS receivers only transmit data through an expansion slot or a cable; a receiver with a cable is often called a mouse GPS receiver because it resembles a computer mouse.

   Such receivers are designed to interface with a laptop computer or PDA running special software. The picture below shows a DeLorme Earthmate GPS unit attached to a laptop. All

GPS data is sent to the laptop and processed there with mapping soft-ware. A Magellan SporTrak GPS receiver is shown on top of the laptop for comparison.

Most GPS receivers that have screens can output data to a PC or PDA.

A GPS receiver’s screen size depends on the receiver’s size. Smaller, lighter models have small screens; larger units sport bigger screens.Generally, a bigger screen is easier to read. Different models of GPS receiver also have different pixel resolutions; the higher the screen resolution, the more crisp the display will be. For night use, all screens can be backlit.

Alarms
A GPS receiver alarm can transmit a tone or display a message when you approach a location that you specify. This feature can be especially useful when you’re trying to find a place and visibility is limited by darkness or inclement weather — or you’re busy doing something else and aren’t looking at the GPS receiver screen.

Built-in maps
Every GPS receiver has an information page that shows waypoints and tracks. The page is a simple map that plots travel and locations. It doesn’t show roads, geographic features, or man-made structures.

Some GPS receivers have maps that show roads, rivers, cities, and other fea-tures on their screens. You can zoom in and out to show different levels of detail. The two types of map receivers areBasemap: These GPS tracker device have a basemap loaded into read-only memory that contains roads, highways, water bodies, cities, airports,railroads, and interstate exits.

Basemap GPS receivers aren’t expandable, and you can’t load more detailed maps to the unit to supplement the existing basemap.

Uploadable map: More detailed maps can be added to this type of unit (in either internal memory or an external memory card). You can install road maps, topographic maps, and nautical charts. Many of these maps also have built-in databases, so your GPS receiver can display restau-rants, gas stations, or attractions near a certain location.

Refer to the picture to see screens from a GPS receiver with a simple plot map and another GPS tracking device with an uploadable map.

GPS receivers that display maps use proprietary map data from the manufacturer. That means you can’t load another manufacturer’s or software company’s maps into a GPS receiver. However, clever hackers reverse-engineered Garmin’s map format. Programs on the Internet can create and upload your own maps to Garmin GPS receivers; GPS mapper is popular.A handheld GPS receiver’s screen is only several inches across. The limitations of such a small display certainly don’t make the devices replacements for traditional paper maps.

Electronic compass
All GPS receivers can tell you which direction you’re heading — that is, as long as you’re moving. The minute you stop, the receiver stops acting as a compass. To address this limitation, some GPS receivers incorporate an electronic compass that doesn’t rely on the GPS satellites.

Operation
Like with an old-fashioned compass, you can stand still and see which direction your GPS receiver is pointing toward. The only difference is that you see a digital display onscreen instead of a floating needle.

On some GPS receivers, you need to hold the unit flat and level for the compass to work correctly. Other models have a three-axis compass that allows the receiver to be tilted.

Paying attention to these factors can improve the performance and convenience of an electronic compass:

   Magnetic fields: Metal objects, cars, and other electronic devices reduce the accuracy of any electronic or magnetic compass.

   Battery life: Using an electronic compass can impact battery life. Some GPS receivers have settings that turn off the compass or only use it when the receiver can’t determine a direction from satellite data.

Calibration: Electronic compasses need to be calibrated whenever you change batteries. If your GPS unit has an electronic compass, follow your user guide’s instructions to calibrate it. Usually, this requires being outside, holding the GPS unit flat and level, and slowly turning in a circle twice.

Altimeter: The elevation or altitude calculated by a GPS receiver from satellite data isn’t very accurate. Because of this, some GPS units have altimeters, which provide the elevation, ascent/descent rates, change in elevation over distance or time, and the change of barometric pressure over time. Calibrated and used correctly, barometric altimeters can be accurate within 10 feet of the actual elevation. Knowing your altitude is useful if you have something to reference it to, such as a topographic map. Altimeters are useful for hiking or in the mountains.

Increasing accuracy
Some GPS receivers have features that allow you to increase the accuracy of your location by using radio signals not associated with the GPS satellites. If you see that a GPS receiver supports WAAS or Differential GPS, it has the potential to provide you with more accurate location data.

WAAS
WAAS is a Federal Aviation Administration (FAA) system, so GPS can be used for airplane flight approaches. The system has a series of ground-reference stations throughout the United States. These monitor GPS satellite data and then send the data to two master stations — one on the west coast and the other on the east coast. These master stations create a GPS message that corrects for position inaccuracies caused by satellite orbital drift and atmospheric conditions. The corrected messages are sent to non-NAVSTAR satellites in stationary orbit over the equator. The satellites then broadcast the data to GPS receivers that are WAAS-enabled.GPS tracker device that supports WAAS has a built-in receiver to process the WAAS signals. You don’t need more hardware. Some GPS receivers support turning WAAS on and off. If WAAS is on, battery life is shorter (although not as significantly as it is when using the backlight). In fact, on these models, you can’t use WAAS if the receiver’s battery-saver mode is activated. Whether you turn WAAS on or off depends on your needs. Unless you need a higher level of accuracy, you can leave WAAS turned off if your GPS receiver supports tog-gling it on and off. WAAS is ideally suited for aviation as well as for open land and marine use. The system may not, however, provide any benefits in areas where trees or mountains obstruct the view of the horizon.

 

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