The accuracy of a electronic tracker

Декабрь 30th, 2015 by homesecuirtycameras and tagged , ,

GPS Sources of accuracy

With satellites, the electronic signals travel about 300,000,000 meters per second (the speed of light). So the errors in the satellite clock and the receiver clock contribute profoundly to errors in distance measurements. One billionth of a second (one nanosecond) of inaccuracy in a satellite clock results in about 30 centimeters (one foot) of error in measuring the distance to that satellite. For this reason, the satellites are equipped with very accurate (Cesium) atomic clocks. Even these very accurate clocks accumulate an error of 1 billionth of a second every three hours. To resolve the satellite clock drifts, they are continuously monitored by ground stations and compared with the master control clock systems that are combinations of more than 10 very accurate atomic clocks. The errors and drifts of the satellites’ clock are calculated and included in the messages that are transmitted by the satellites. In computing the distance to the satellites, GPS 3G receivers subtract the satellite clock errors from the reported transmit time to come up with the true signal travel time. Even with the best efforts of the control centers in monitoring the behavior of each satellite clock, their errors cannot be precisely determined. Any remaining satellite clock errors accumulate typically to about a few nanoseconds, which cause a distance error of about one meter.

the accuracy of our computed position also depends on how accurately we know the location of the satellites (the points of references). The orbits of satellites are monitored continuously from several monitoring stations around the earth and their predicted orbital information is transmitted to the satellites, which they in turn transmit to the receivers. The history of GPS has shown, thus far, that the accuracy of the orbital prediction is in the order of a few meters. This will create about a few meters of error in computing our position.

GPS receiver

A fair number of geocachers use only their GPS tracking device for cars to get them to a cache, but a good local map of the area can be very helpful. Although a receiver can lead you directly in a straight line to cache, it’s probably not going to tell you about the river, deep canyon, or cliffs between you and the cache. Even GPS receivers that display topographic maps often won’t show enough detail that can help or hinder you on your way to a cache. Additionally, a map and compass serve as a backup just in case something goes wrong with your GPS.

You can certainly find caches by using only a map and compass (my adventure racing team does this to practice our navigation skills), but it’s sure a lot easier when using a GPS receiver. You don’t need an expensive GPS unit with lots of whistles and bells to geocache; a basic model around or under $100 will work just fine; receivers that support WAAS (Wide Area Augmentation Service) usually are more accurate than those that don’t. Don’t forget to bring the GPS receiver user manual, especially if you just purchased your receiver and are still trying to figure out how to use it.

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Using GPS Tracking Device will enhance your basic navigational skills

Декабрь 29th, 2015 by homesecuirtycameras and tagged , , ,

Most GPS receiver cases have a loop on the back to hold the case on a belt. If you’re wearing shorts or tights and don’t have a belt, waist packs for carrying a radio or a cassette/CD player are an option. These packs can accommodate larger GPS receivers. They’re not very noticeable when you’re working out because they’re designed not to bounce much. Small fanny packs and waist packs that carry water bottles also carry a GPS receiver. If the GPS receiver is small, try carrying it in your front pants pocket. I’ve carried a GPS while running and cross-country skiing in trail-running shorts and tights with zipper pockets. Although satellite reception is sometimes lost while under heavy tree cover, the GPS receiver records track data as long as I have a mostly clear view of the sky.

Using GPS will greatly enhance your understanding of the map-and-compass technique, but it’s wise to hone basic navigational skills before or in conjunction with use of a GPS tracking device. When out in the field, you will develop your own style of GPS use. You may want to plot a course ahead of time, upload it to your GPS, and follow that. You may want to upload only key points of your journey such as crucial trail intersections, waterfalls, high points, or shelter locations. You may want to carry the GPS along without uploaded data and navigate without the aid of pre-plotted track points or waypoints. Or you may just want to have the GPS to turn on once or twice a day to check your position against a map.

The Timex Speed + Distance system is a cigarette pack-size GPS magnetic tracker that straps on your arm and transmits data to a special wristwatch. You can look at your watch and see how far you’ve gone and how fast you’re going. Timex updated the system in 2003, adding more components and calling it Bodylink. In addition to the GPS receiver and watch, the Bodylink includes a heart-rate monitor (the GPS receiver, watch, and heart-rate monitor ) and a data recorder that collects data from both the GPS receiver and the heart-rate monitor. You can connect the data recorder to your personal computer to upload your workout data and analyze it with the included software.

Even with vehicle GPS tracking device technology becoming better every day, it is still a good idea to have backup navigation. Having a paper map, a simple compass,and knowledge of manual navigation is a good, safe practice of prudent navigators! Remember, GPS is a complement to navigation and should not be the only navigational tool you use.

The main disadvantage to carrying your GPS receiver on or below your waist is that it’s not the best place for satellite reception. There’s a good chance that you’ll lose the signal in areas with reduced satellite coverage. If you use a hydration pack or a lightweight backpack, you can get your GPS higher for better satellite reception by mounting the case either on one of the front shoulder straps or putting the GPS receiver in the upper, top pocket of your backpack. (It isn’t as accessible in the backpack pocket but should get good satellite reception.

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GPS tracking solutions —— basic knowledge about GPS system

Декабрь 28th, 2015 by homesecuirtycameras and tagged , , ,

Today, GPS (  GPS for vehicle ) is causing a renaissance of the navigation, surveying and mapping professions and may, within only a few years, completely replace conventional methods of transportation navigation and land surveying. The uses and implications of the GPS system are yet to be fully realized, and new applications are being found at an ever-increasing rate. There are three parts to the GPS system: the satellite segment, the user segment, and the control segment.

Control segment

This part keeps the whole system running smoothly. Satellites need to be kept in their proper orbits and their signal transmissions kept up-to-date. The Air Force operates a series of five ground stations around the globe, typically at exotic tropical locations: Hawaii, Ascension Island, Diego Garcia, Kwajalein, and the decidedly nontropical master station in Colorado Springs. You’ll probably never think about the control segment, but without it, the entire system would quickly fall into disrepair.

Satellite segment

Satellites are the heart of the Global Positioning System. They broadcast the signals your receiver uses to determine your position. At least 24 satellites are in operation at all times, each orbiting the earth every 12 hours (or 11 hours and 58 minutes, if you want to be precise). Their orbits are designed so that, theoretically, at least 6 and as many as 12 satellites are above the horizon virtually all the time, regardless of where you are. “Theoretically” is the key word here—the satellite signals don’t travel through mountains, buildings, people, or heavy tree cover, so unless you’re on a flat plain or body of water, some signals probably will be blocked. Since your receiver must lock onto at least four satellites to accurately determine its position, you may have to move around to get better reception. (By the way, it’s a little-known fact that all GPS satellites perform a second duty: Each includes an X-ray detector that lets the U.S. government monitor nuclear explosions anywhere in the world.)

User segment

Your handheld receiver makes up the user segment. There’s a lot of power inside that little package. Not only does it contain a sensitive receiver capable of detecting signals less than a quadrillionth the power of a light bulb, it also includes a powerful computer that converts the raw data into such useful information as your position and speed. A GPS magnetic tracker doesn’t include any kind of transmitter, meaning it is a passive positioning system—you can determine your own position, but there’s no way for anyone else to use it to track you.

However, accuracy can be improved by combining the electronic tracker with a Differential GPS (or DGPS) receiver, which can operate from several possible sources to help reduce some of the sources of errors described above. Differential GPS works by placing a GPS receiver (called a reference station) at a known location. Since the reference station knows its exact location, it can detennine the errors in the satellite signals. It does this by measuring the ranges to each satellite using the signals received and comparing these measured ranges to the actual ranges calculated from its known position. The difference between the measured and calculated range.

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How GPS tracker work - Time is of the Essence

Декабрь 25th, 2015 by homesecuirtycameras and tagged , ,

With progressive development in technology in recent years, one can relish the prime advantages of the various innovative software solutions such as field service tracking software. A lot of operational costs can be reduced using this software to improve the ROI. From various records, it is also proven that many industries have saved up to 30% using the field service tracking system. The best thing about using this software is that, it can be accessed from computers, smart phones or tablets. In addition to these types of GPS receivers, larger and less portable models are used in airplanes, boats, and commercial vehicles. The U.S. government and military uses restricted-use GPS units, and expensive receivers are used for surveying. Although some of these vehicle GPS tracking devices are discussed briefly, don’t expect to find out as much about them as the land and auto consumer models. I tell you what questions to ask when selecting a GPS receiver and give you some hints on which features are best for different activities. You can apply these questions and selection criteria to pretty much any GPS 3G tracker for Car to pick the right model for you.

In a conventional Personal GPS tracker the information, such as carrier frequency and initial C/A code phase obtained from the acquisition, can be used to track a signal. The navigation data phase transition can be found through the tracking program. For a weak signal it is difficult to determine the exact location of the navigation data transition from the tracking program. In order to process the data efficiently, the exact location of the navigation data phase transition is needed such that one can start to process the data every 20 ms. Thus in this section the determination of the location of the navigation phase transition is discussed. In general, it is easier to determine whether there is an existence of data transition than to determine the exact location of a data transition.

Even though the vehicle GPS tracking device knows the precise location of the satellites in space, it still needs to know how far away the satellites are (the distance)so it can determine its position on Earth. There is a simple formula that tells the receiver how far the satellites are (the distance)so it can determine its position on Earth.  There is a simple formula that tells the receiver how far it is from each satellite:Your distance from a given satellite object equals the velocity of the transmitted signal multiplied by the time it takes the signal to reach you (Velocity x Travel Time = Distance).

The satellites orbit at an altitude of approximately 20,200 kilometers, or about half the altitude of a geostationary satellite. A geostationary satellite, orbiting at about 40,000 kilometers altitude, circles the Earth every 24 hours, the same time period that the Earth takes to complete one full rotation (one day). Therefore, a geostationary satellite always remains over the same spot on the Earth (thus “geostationary”), essentially following that “spot” on the surface as the Earth rotates. The GPS satellites, at one-half that altitude, complete one orbit every 11 hours, 58 minutes (its “orbital period”). Since the Earth is rotating underneath the orbiting satellites, any given satellite’s orbit slowly “moves” slightly westward with each rotation.

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Causes of electronic tracking devices position errors

Декабрь 24th, 2015 by homesecuirtycameras

Technology has drastically advanced and unlike the past when people needed a special satellite GPS receiver to track movements, today the 3G GPS are found in smart phones and other small gadgets. They work by connecting to the internet connection as well as receiving a signal directly from the GPS satellite, which helps pinpoint the exact location of the GPS signal. This has proven to be a truly important tool for automobile owners since the Car GPS tracker can be installed in a secret location on a vehicle allowing security personnel to track the signal from the vehicle and locate the vehicle.

Now the GPS receiver needs to determine the time part of the formula. The answer lies in the coded signals the satellites transmit. The transmitted code is called “pseudo-random code” because it looks like a noise signal. When a satellite is generating the pseudo-random code, the vehicle GPS tracking devices is generating the same code and tries to match it up to the satellite’s code. The receiver then compares the two codes to determine how much it needs todelay (or shift) its code to match the satellite code. The accuracy of our computed position also depends on how accurately we know the location of the satellites (the points of references). The orbits of satellites are monitored continuously from several monitoring stations around the earth and their predicted orbital information is transmitted to the satellites, which they in turn transmit to the receivers. The history of GPS has shown, thus far, that the accuracy of the orbital prediction is in the order of a few meters. This will create about a few meters of error in computing our position.

Causes of GPS position errors

The global positioning system is afflicted by many technical problems and uncontrollable natural phenomena that affect the accuracy of a GPS position fix. A worst-case scenario would be if your Personal GPS tracker broke down or the whole GPS system stopped working. Some less severe but common causes of position error are discussed below.

1. Deliberate signal degradation

The people who operate the global positioning system are able to deliberately degrade the timing of the signature signals to selected parts of the world. A less accurate position reading in that region would result. The position error can be made arbitrarily large.

2. Satellite distribution

Because of the inherent constraints of geometry, the distribution of the visible satellites affects the accuracy of your position. Ideally, all the visible satellites should be evenly spaced across the sky. In practice, the satellites are never perfectly distributed. The position accuracy degrades in proportion to how close the visible satellites are clustered together.

3. Signal obstructions

Obstructions such as trees or adjoining terrain that block the satellite signals are the most common cause of position errors or inability to get a position fix. The greater the number of satellite signals that reach your receiver and the stronger the satellite signals, the better the accuracy. Most receivers attempt to calculate a two dimensional position fix after obtaining signals from just three satellites. The receiver does this by assuming that it is at a known elevation, usually sea level or the elevation of its last position fix. If the assumed elevation is significantly wrong, the calculated two-dimensional position could be off by a kilometer or more. Manually inserting the correct elevation into the receiver will alleviate this problem

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Essential applications for electronic tracker

Декабрь 22nd, 2015 by homesecuirtycameras and tagged , ,

motorcycle GPS tracker are designed with many built-in features but only a few are essential for wilderness navigation. Any feature that requires the tracker to stay switched on for prolonged periods should be used sparingly as conserving battery power is an important consideration, especially in cold weather.

Not all GPS receivers can display maps. Lower-cost models (typically under $150) or GPS receivers with very small screens usually don’t support maps. If you already own a GPS receiver, make sure that it’s compatible with the map software you’re interested in using. Manufacturer Web sites are pretty good about listing product compatibility. The same holds true if you’re shopping for a new GPS receiver.

You can use only proprietary products (made by the same company that manufactures your GPS tracker). Admittedly, I’m belaboring this point, but a fair number of novice GPS users think that they can load just about any map on their new GPS tracker, which isn’t the case.

Don’t expect the level of detail in a GPS map to match paper maps. In order to maximize memory space, Magnetic GPS use vector maps (created with lines and shapes) instead of raster maps (scanned paper maps). And because a GPS tracker has a fairly small screen to display a map, don’t expect the map on your GPS tracker to appear as an identical version of your favorite paper map. Until tracking devices for people incorporate science-fictionlike, holographic projection systems where a map appears in midair (and I’m not holding my breath), viewing a paper map will always be easier and more effective than staring at a map on a GPS tracker.

Determining your position

The ability to pinpoint your position during any type of weather almost anywhere on Earth is the most basic application of a waterproof tracking devices. Just switch on the tracker and wait for a position fix. Your position can be displayed as a grid number, a geographic coordinate, or a point on a built-in digital map. With signals from a minimum of four satellites, the tracker will display your elevation.

Storing a position as a waypoint

A waypoint is simply a named set of coordinates representing a position. Once your tracker has acquired a position fix, you can store the position in the tracker’s memory as a waypoint. This is very useful for finding your way back to the position. You could also give the waypoint’s coordinates to someone else, who could then find the waypoint with his or her own tracker.

Inserting a waypoint

You can manually key a position into your tracker’s memory as a waypoint without ever having set foot at that location. The coordinates for the waypoint could be obtained from a printed map or from someone else who has previously been there. With a computer, you can insert waypoints electronically into a GPS tracker from a digital map.

Navigating toward a waypoint

Finding your way toward a stored waypoint is the essence of GPS navigation. With waypoints stored in its memory, switch on the tracker and let it acquire a position fix. With a few keystrokes, the tracker will display the distance and bearing toward any stored waypoint. There are two primary ways to navigate toward a stored waypoint: (1) using the tracker by itself, or (2) using it together with a compass. By itself, the tracker must be switched on continuously. With a compass, the tracker requires only intermittent use with most of the navigating done by the compass.

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