#electronic tracker

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Since the early commercial Wireless GPS Tracking Device industry was heavily influenced by highprecision survey and mapping applications, there has been much research on GPS multipath. But the multipath that has been studied is mostly two-ray multipath, in which the direct and reflected signals are both present at the antenna. The problem faced by high sensitivity GPS is not so much two-ray multipath, in which there is a longer delay from the reflected path, but rather pure reflections in the absence of a detectable direct signal. There has recently been an increase in attention paid to the urban canyon problem. See, for example, though the focus is still mostly on two-ray multipath. We must also note that the reflected signal at the antenna is not necessarily coming from a single source. In fact, it is usually not. Usually there are many reflected paths that lead to the antenna, and thus, if the signals interfere constructively, you will observe relatively strong signals that are nonetheless pure reflections.

The fields in the ionosphere model GPS assistance data is considered to be global in nature because it is not specific to any particular satellites. The LS simply uses the data that it has cached from the GRS and encodes it into the format specific to the protocol being used. Instead of encoding this data type on a per-request basis, the LS will generally encode it as a changed version is received from the GRS. That way, it does not need to be encoded for every request, but is just copied to the appropriate place in the bit buffer for the message being composed by the LS. This data type is only applicable to handset-based A-GPS, which uses it for part of the position calculation and may also use it to calculate acquisition data. The next question after creating the Route and Position methods is how to fill a route with plausible real-world data. The obvious solution is a global navigation satellite system (GNSS) or global positioning system (GPS). While Electronic Tracking Device is the currently used shortened acronym, it was derived from NAVSTAR GPS (Navigation System for Timing and Ranging), the first actual global positioning system, launched in 1971.

About 24 satellites orbit the earth. With at least four satellites (three for position, one for time) in sight, a GPS Tracking Device is able to calculate its (lat, lon) location with a certain precision and speed, depending on a number of factors. In addition, many GPS devices are able to mark and record (or even transmit) the current position. More sophisticated units allow the user to create and store routes as well as load (digital) maps to be displayed on a small screen. A simple mouse could be considered a GPS representing Position in the software world. GPS systems are becoming more and more prevalent and can be found in a growing number of devices (cell phones). From the abstracted project view, a GPS is simply an arbitrary technical system to enable electronic receivers to determine their current longitude, latitude, and elevation information. Part of our task is to create a GPS receiver for the software world, a GPS unit. Every RO will have a built-in virtual GPS receiver.

Most of the error in GPS positioning comes from medium propagation effects that are unpredictable or difficult to model, including multipath (reflection of the signal before it finds the antenna) and tropospheric refraction. If one considers the basic error and operational characteristics of the INS, then a clear complementarity to GPS emerges. INS is very precise in the short term and yields data rates much higher than GPS. It is self-contained (Personal Tracker), except for initialization, and operates in any environment. On the other hand, GPS positioning is very accurate in the long term (drifts can be eliminated largely through data processing), it depends on a space segment that provides accurate orbit information, GPS data rates are only *noderatelyhigh, and the operational environment may limit the positioning capability. The integration of GPS and INS is the subject of Chapter 10; while, in the present chapter we review the essentials of obtaining observations with the Global Positioning System, aiming primarily at kinematic applications. It is beyond the present scope to expound in detail on the many aspects of the Global Positioning System including the broad range of applications,

There are several quantities that may be observed with a Waterproof GPS Tracker ; not all are routinely provided by every receiver. However, in one way or another, these observables are all connected to time, and time on board the satellite and in the receiver is kept by clocks that are, in fact, generators oscillating at a particular frequency. These oscillators are also responsible for generating the signals that are used to form the observables. But GPS is not without problems and limitations. In the first place, it is not a selfcontained, autonomous system like INS. The user must be able to "see" (in the sense of being able to receive transmitted signals from) the GPS satellites. Usually this is no problem, but satellite visibility may be obstructed locally by intervening buildings, foliage, mountains, bridges, and tunnels. This is because the carrier signal that the satellite transmits and that conveys positioning codes and the navigation message has a wavelength only 19 cm long (-1.6 GHz signal) and so will be severely attenuated even with light to moderate foliage and completely blocked by most larger structures. Certainly, direct underwater applications of GPS are completely impossible.

Although this signal shadowing is the most restrictive limitation, other problems with Portable GPS Tracking prevent it from realizing the required accuracy and resolution in many kinematic applications. One of these arises from the effects of electronic interference or brief obstructions that may cause the receiver to miss one or more cycles of the carrier wave (this matters only if the carrier phase rather than the code is used for positioning). In fact, jamming and sustained electronic interference are general problems. The frequency of the data output in most receivers is often 1 Hz, rarely greater than 2 Hz without significant increase in the noise levels. This may not yield sufficient resolution or accuracy for airborne platforms that collect scientific data at a higher rate or at random intervals not precisely coincident with the GPS epochs.