Introduction to GPS and Waas

Well, now you know the basics of how the unit does its work. You might be ready to jump ahead to Section 2, Installation & Accessories, on page 11, so you can mount your IntelliMap 640c and plug in the power. Or you might want to see how our text formatting makes the manual tuto- rials easy to skim. If that's the case, move on to "How to Use This Man- ual" on page 8. But, if you want to understand the current state of sat- ellite navigation, look over this segment describing how GPS and its new companion WAAS work together to get you where you're going.

The Global Positioning System (GPS) was launched July 17, 1995 by the United States Department of Defense. It was designed as a 24- hour-a-day, 365-days-a-year, all weather global navigation system for the armed forces of the U.S. and its allies. Civilian use was also avail- able at first, but it was less accurate because the military scrambled the signal somewhat, using a process called Selective Availability (SA).

GPS proved so useful for civilian navigation that the federal govern- ment discontinued SA on May 2, 2000, after the military developed other methods to deny GPS service to enemy forces. Reliable accuracy for civilian users jumped from 100 meters (330 feet) under SA to the present level of 10 to 20 meters (about 30 to 60 feet.)

Twenty-four satellites orbit 10,900 nautical miles above the Earth, passing overhead twice daily. A series of ground stations with precisely surveyed locations controls the satellites and monitors their exact locations in the sky. Each satellite broadcasts a low-power signal that identifies the satel- lite and its position above the earth. Three of these satellites are spares, unused until needed. The rest virtually guarantee that at least four satel- lites are in view nearly anywhere on Earth at all times.

A minimum of three satellites are required to determine a 2D fix.

640c, Mapping GPS Receiver specifications

Eagle Electronics has made a significant mark in the world of marine electronics with its innovative and reliable products, notably the Eagle Electronics 640C, 640cDF, and the 640c models. These devices are designed for anglers and navigators who seek advanced functionality combined with user-friendly operation.

The Eagle Electronics 640C is a high-performance fish finder that is primarily admired for its vibrant display and precise mapping capabilities. Equipped with a 640x480 pixel, full-color LCD screen, it provides crystal-clear visibility even in bright sunlight. This device uses advanced sonar technology to offer detailed underwater images, allowing users to locate fish with remarkable accuracy. The high-resolution graphics enhance the experience while providing an intuitive interface for easy navigation through its various features.

The 640cDF, a variant of the 640C, elevates the standard fish finder experience by incorporating dual-frequency sonar capabilities. This model operates on both 200 kHz and 83 kHz frequencies, allowing users to switch between narrow and wide beams based on their fishing needs. The dual-frequency technology provides a more comprehensive view of the underwater environment, making it easier to identify different types of fish and underwater structures. Additionally, the 640cDF boasts temperature sensing capabilities, giving anglers valuable data regarding water conditions that can influence fish behavior.

All models in the Eagle 640 series feature built-in GPS navigation. The integrated GPS provides a reliable mapping system that allows users to mark waypoints and create routes, significantly improving navigation efficiency. This technology is vital for those who engage in long-distance fishing trips or travel in unfamiliar waters. The GPS functionality, combined with the sonar capabilities, makes these devices essential tools for successful fishing excursions.

Furthermore, the Eagle 640 series devices come equipped with customizable display options, allowing users to tailor the information presented based on their preferences. The intuitive menu system simplifies the navigation of the device's various features, empowering users to quickly access critical data without unnecessary complications.

In summary, the Eagle Electronics 640C, 640cDF, and the 640c represent a blend of cutting-edge technology and user-centric design in the marine electronics space. With features such as high-resolution displays, dual-frequency sonar, built-in GPS navigation, and customizable settings, these devices enhance the fishing experience, making them invaluable assets for anglers and navigators alike.