To keep from getting lost, our ancestors had to go to pretty extreme measures: they erected monumental landmarks, laboriously drafted detailed maps and learned to read the stars in the night sky.

Today, things are much easier. When people talk about “a GPS,” they usually mean a GPS receiver. The Global Positioning System (GPS) is a satellite-based navigation system originally intended for military use, but in the 1980s, the government made the system available for everybody. GPS works in any weather conditions, anywhere in the world, 24 hours a day.

In this article, we will explore the different types of GPS and Navigation devices, along with their different functions and technologies.

Basic Concept of GPS

GPS satellites circle the globe in a very precise orbit and transmit signal information to Earth. These satellites make two complete rotations every day and are arranged so that at any time, anywhere on Earth, there are at least four satellites “visible” in the sky. GPS receivers take this information and use triangulation to calculate the user’s exact location.

Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from four or more satellites, the receiver can determine the user’s position and display it on the unit’s electronic map.

Dedicated GPS Navigation Devices

Once the user’s position has been determines, the GPS unit can calculate other information, such as:

•    Speed, distance, altitude and time
•    Maps, including street maps, displayed in readable format via text or in a graphical format
•    Turn-by-turn navigation directions via text or speech
•    Traffic congestion maps (depicting either historical or real-time data)
•    Suggested alternate directions or shortest routes
•    Information on nearby amenities such as restaurants, gas stations and tourist attractions

Dedicated devices have various degrees of mobility. Hand-held, outdoor or sport receivers have replaceable batteries that can run them for several hours, making them suitable for hiking, bicycle touring and other activities far from an electric power source.

Other receivers are intended primarily for use in a car, but have a small rechargeable internal battery that can power them for an hour or two away from the car. Special purpose devices for use in a car may be permanently installed and depend on the automotive electrical system.

GPS in the Car

Automotive GPS units can either be professionally installed, or mounted on the windshield or dashboard. Today’s standalone GPS devices offer a lot more than they ever have, and they’ve become more affordable. From free traffic reporting and lifetime map updates to local search for shopping and restaurants, GPS units for the car are easy to use and accessible.

The major difference between one vehicle GPS device and another is often in the features: voice recognition, real-time traffic data, red light and speed trap warnings, trip logs that record your progress, upgradeable maps, and useful extras like Bluetooth integration, MP3 players and picture viewers.

GPS for Fitness

A GPS watch is a device with an integrated GPS receiver that is worn as a single unit strapped onto a wrist, in the manner of a watch. The watch can have other features and capabilities depending on its intended purpose. GPS watches are most often used for sports and fitness purposes. Many can connect to external sensors by the wireless ANT+ protocol, and/or by USB to transfer data and configuration.

Often GPS watches include loggers that record trip information for download, and need to be connected to a computer to be used (via a Bluetooth or USB connection). This kind of GPS tracking is useful for trailblazing and mapping by hikers and cyclists.

GPS on the Water

A chartplotter is a device used in marine navigation that integrates GPS data with an electronic navigational chart (ENC). The chartplotter displays the ENC along with the position, heading and speed of the ship, and may display additional information from radar, automatic information systems (AIS) or other sensors. Chartplotters may also display data from other sensors, such as echolocators/sonar.

A basic navigational display is common to all chartplotters. Depending on intended use and characteristics of the specific chartplotter, they may have options to present such displays as three-dimensional fish-finding and bottom characteristics useful in fishing.