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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