followers 0 popularity
3
following 0
Groups
electronicsmandy is not in any groups

Interests

electronics, technology
mandylulu | electronicsmandy

Portable tracker is a parallel multi-channel design

Dec 24th 2015 at 2:01 AM

Most modern Motorcycle GPS are a parallel multi-channel design. Older single-channel designs were once popular, but were limited in their ability to continuously receive signals in the toughest environments — such as under heavy tree cover. Parallel receivers typically have from between five and 12 receiver circuits, each devoted to one particular satellite signal, so strong locks can be maintained on all the satellites at all times. Parallel-channel receivers are quick to lock onto satellites when first turned on and they are unequaled in their ability to receive the satellite signals even in difficult conditions such as dense foliage or urban settings with tall buildings.

 

Although survey-grade GPS tracker mini can provide accuracy of less than two centimeters, they are very specialized and expensive, require a lot of training, and aren’t very portable. Their accuracy is achieved with DGPS and postprocessing collected data to reduce location errors. The average GPS user doesn’t need this level of precision. Clouds, rain, snow, and weather don’t reduce the strength of GPS signals enough to reduce accuracy. The only way that weather can weaken signals is when a significant amount of rain or snow accumulates on the GPS receiver antenna or on an overhead tree canopy.

 

The impact of the ionosphere on electronic signals depends on the frequency of the signal. The higher the frequency, the less is the impact. So if we transmit the patterns simultaneously via two different frequencies, the ionosphere may delay the code on one frequency, for example, by 5 meters and on the other frequency, say, by 6 meters. We cannot measure the magnitude of these delays, but we can measure their difference by observing the difference on their arrival time, which in this case translates into 1 meter of effective distance between them. By measuring this difference and using known formula for frequency dependency of the ionosphere delay, ionosphere effect can be removed. It is exactly for this reason that all GPS satellites transmit information in two frequencies, called L1 and L2. Precision receivers track both signals to remove the effect of the ionosphere. All non-precision receivers track only the L1 signal. This is one of the main distinguishing features between different types of receivers. The L1 receivers are also called single frequency receivers, while the receivers that track L1 and L2 are called dual frequency receivers. Dual frequency receivers practically remove the ionosphere effects.

 

All satellites in the GPS constellation continuously broadcast a digital radio signal, embedded with its position and the time. Basically tracker for vehicle lock on to these radio signals, compare the unit’s time with the satellites’ times, compute the differences, and then plot a position point. Each satellite will continuously broadcast direct sequence, spread-spectrum signals on which passive receivers can perform precise ranging measurements. Each broadcast is also modulated with a navigation message,which is developed by the ground control segment and describes the satellite location and clock offset. For each of several satellites, the user equipment measures a "pseudorange" and demodulates the navigation message. A pseudorange is equal to the true range plus an unknown bias equal to the difference between the receiver clock and GPS system time. Pseudorange measurements to four well-spaced satellites are sufficient to solve for the user's three-dimensional position and clock.

0 comments
Please to comment

sign in

Username
Password
Remember Me


New to IM faceplate? join free!

Lost Password? click here