How to Select a GPS Receiver

The Global Positioning System (GPS) is a satellite-based navigation system made up of 24 satellites, 21 primary satellites and three back-up satellites that circle the earth twice a day in a regular orbit at an altitude of 10,900 miles. The satellites were put into orbit by the U.S. Department of Defense and were originally intended for military applications but were made available for public use in the 1980s.

The GPS satellites transmit signal information to a handheld GPS receiver which takes the information and uses it to calculate the receiver’s position. It does so by measuring the travel time of radio signals from the available satellites to the receiver and gives a reference point or position in coordinates.

A GPS receiver requires a minimum of three satellites to calculate the receiver’s latitude and longitude and to track movement. If four or more satellites are in view the receiver can determine the user’s latitude, longitude and altitude. Once a position has been determined the GPS receiver can calculate other information such as speed, bearing, track, trip distance, etc.

Common uses for a GPS receiver include:

• Knowing the exact speed and distance of travel
• Tracking a path while walking or hiking
• Pinpointing specific locations on water or in the woods so that location can easily be relocated
• Getting to a specific location in an unfamiliar area
• Calculating acreage or area, mapping fields or marking areas of weed infestation.

Waypoints
A waypoint is a position or location that is entered and stored in the GPS by the user at any given time. An example of waypoint may be a check point on a route or a feature such as camp, a vehicle, a fork in the trail or just a favorite spot.

GPS receivers allow you to name your waypoint or identify it with a symbol. The number of waypoints that can be stored depends on the unit; the smaller receivers can store approximately 500 while some larger receivers can store up to 1000.

Routes
A route is group of waypoints that are entered into the GPS receiver in a sequence that will get the user from one specific location to another.

Auto Routing
GPS receivers equipped with auto routing will automatically route the user to a specified destination using specific turn-by-turn instructions.

Track Log
A track log is similar to a bread crumb trail. It marks the trail as the user travels and allows the user to retrace their path in either direction.

Non-Mapping/Base-Mapping/Mapping GPS Receivers
Non-mapping GPS receivers are the most basic and generally have no map detail. The plotter screen shows the path by tracking waypoints, routes or track logs from one to another. Non mapping GPS receivers will also note the time of day, latitude and longitude similar to how a compass works.

Base-mapping GPS receivers have the same tracking, plotting and route features as non-mapping units, but include a map to help determine location. Base-mapping units will typically show state, interstate and U.S. highways, major thoroughfares in metro areas, lakes, rivers coastlines, airports and exit locations. They can also determine current location, speed of travel and direction of a destination. Base-mapping GPS units are good when a map is unavailable, but necessary for determining the final location of a destination.

Mapping GPS receivers can capture information that is entered into the receiver and transmit it to a computer through a USB cable. Depending on the amount of memory available, a mapping unit can be personalized by uploading area or road maps from a DVD or memory card. Please note that because the amount of memory varies from GPS receivers, it is important to choose the receiver and software carefully.

Memory
Is necessary for downloading or adding maps to the receiver. Depending on the GPS model memory is either fixed and cannot be added to or expandable and can be added to by using a MicroSD/SD card.

Battery Life
Varies anywhere from 16-24 hours on 2 "AA" batteries in handhelds or 5-8 hours for a lithium ion rechargeable battery in driving GPSs. To find out what the expected battery life for each unit Gempler’s carries please see our GPS Product Comparison chart.

Screen Size
Is also a consideration depending on application. For the screen size of each GPS receiver please see our GPS Product Comparison chart.

Gray Scale or Color Screen
Receivers are available in both gray scale or color and one may be preferred over another depending on the application. If the receiver is being used for basic mapping or area calculation applications black & white may be adequate and less expensive. If the receiver is being used for hiking or hunting applications a color screen is nice because the color shading shows changes elevation and formations.

Area Calculation
There are a variety of the handheld GPS receivers that can be used to calculate area or acreage to an accuracy of plus/minus 3 meters. To see which receivers will calculate area, please see our GPS Product Comparison chart.

Electronic Compass
An electronic compass does not rely on satellite signal or movement to determine direction; instead it will give direction even if a GPS signal is not available. This feature is especially useful in applications such as hiking in unfamiliar or heavily wooded areas where satellite reception may not be ideal.

Barometric Altimeter
Will give accurate elevations ranging from -2000 to 30,000 feet. A barometer can also be used to track weather patterns; a falling barometer that may result in rain, a rising barometer that means the weather is clearing. It is a good feature for outdoor applications such as hiking or hunting and is often available on a GPS receiver along with an electronic compass.

PC Interface
All GPS receivers are able to interface with a computer by using either a serial or USB port. To find out which type of PC interface each GPS receiver has please see our GPS Product Comparison chart.

Antenna
The majority of the receivers have an internal antenna built into the unit. An external antenna may also be required when using the receiver under dense cover, in areas where the GPS receiver does not have a clear view of the sky or when more satellite contact is necessary for a greater amount of accuracy.

How do I select which GPS receiver will be best for my application?

The first thing to determine is how you will be using the GPS.

1. Do you plan on using it for outdoor activities such as hiking, walking or biking? If so, one of the handheld GPS units would be best depending on which features you require.

2. Do you plan to use it in your car? If yes, a personal navigator such as the Nuvi would be a good choice because it offers voice prompts that announce streets by name, gives driving directions and has a bigger, more visible screen.

Then determine which features you need or want depending on your application. If, for example, you are interested in a handheld receiver do you want one with a gray or color display? Also if you plan on adding additional maps you will need a GPS with a large amount of memory or expandable memory depending on the type of map?

Other features to consider for handhelds are an electronic compass, barometric altimeter or a receiver that is able to calculate area. For a guide to the features that are available on each GPS receiver please see our GPS Product Comparison chart.

How accurate is a GPS receiver?
A GPS receiver is accurate to plus/minus 3 meters, the more satellites it can contact the more accurate it will be.

Can a GPS be used under a forest canopy or near tall buildings?
Any obstruction can decrease signal strength, trees, tall buildings and even transmissions from microwaves can affect GPS signal reception. Some GPS receivers may be able to capture satellite signals under light forest cover better than others, but all will begin to lose satellite reception in dense cover.

Which receivers can be used to calculate area?
The majority of the handheld GPS’s can be used to calculate area or more specifically acreage. To determine which will do so please reference our GPS Product Comparison chart.

Is it okay to use a handheld GPS on a motorcycle?
Garmin does not suggest using a handheld GPS on a motorcycle due to the vibration and humidity that the receiver is exposed to. Instead they suggest purchasing one of the motorcycle-ready units that is built to withstand such conditions.

Are the handheld GPS receivers waterproof?
Receivers that are noted as being waterproof meet the European IPX7 standard. If the receiver is considered waterproof the case can withstand accidental immersion in up to one meter of water for up to 30 minutes.

Is it important to register a new GPS?
Garmin suggests registering a new GPS within the first 60 days. This will allow the user access to map or software updates and also validates ownership if the receiver is lost or stolen.

Can other manufacturer’s maps be used on a Garmin GPS?
Only Garmin maps will display on Garmin GPS receivers. There are four types of maps available from Garmin, Topo which is for outdoor enthusiasts and includes detail for an area down to each hill and valley, Inland Lake which details freshwater lakes, Coastal for marine applications, and Street for mapping. Maps are available on DVD or preloaded on a microSD/SD card that can be inserted into a GPS.

What if I want to use my GPS outside of the US?
The Global Positioning System or satellite system works in all weather conditions, anywhere in the world, at any time of the day. A handheld GPS receiver can be used but will need to be updated to include maps for the country in which it will be used.