Appreciate the help! I guess your gps software does not any nmea frame in com5. You can try using at! I did: at! I will try that Thanks, Linda Did you catch all of that? If not or if you want more, check out a much more detailed explanation, in volume 1 of GPS Fundamentals by Dan Doberstein. Volume 1 has been released for free, but you must support the author to read volume 2. An artist's rendition of the control segment.
Along with satellites and GPS receivers, there are ground based stations that can communicate with the satellite network and some GPS receivers. This system is formally called the control segment and increases the accuracy of your GPS receiver. DGPS units are also expensive and tend to be larger because they require an additional antenna.
GPS Accuracy depends on a number of variables, most notably signal to noise ratio noisy reception , satellite position, weather and obstructions such as buildings and mountains. These factors can create errors in your perceived location. Signal noise usually creates an error from around one to ten meters.
Mountains, buildings and other things that might obstruct the path between the receiver and the satellite can cause three times as much error as signal noise. A GPS receiver must be able to get a lock on 4 satellites to be able to solve for a position.
The first lock it gets allows the receiver to obtain the almanac information and thus what other satellites it should listen for. Although it is possible to get a position from less than 4 satellites, the margin of error of this position can be rather large. Your most accurate read of your location comes when you have a clear view of a clear sky away from any obstructions and under more than four satellites.
To combat these errors, a couple of different assistants have been created. This method uses wireless ground-based networks to help relay between the satellite and the receiver when the GPS signal is weak or not able to be picked up. There are two ways AGPS can help out. The first is to provide the receiver with the proper almanac data and the precise time. The second utilizes the higher computing power and good satellite signal of the ground base to interpret the broken or fragmented information the receiver is receiving to provide a more accurate position reading to the receiver.
When communicating with these receivers, the GPS can acquire a lock on the satellite more quickly as well as receive more accurate information. But AGPS is present in more devices than just cellphones; it's even available in cameras and some vehicles. DGPS also uses ground or fixed GPS stations to determine the location, but differs in that it finds the difference between both the satellite and the ground location reading.
These ground stations may be up to nautical miles from the receiver, and it is important to note that accuracy deteriorates the further you are from the ground station. DGPS is accomplished by a ground station broadcasting a signal which dictates the error between the actual pseudorange and the measured pseudorange. This value is calculated by multiplying the speed of light by the time it takes the signal to travel from the satellite to the receiver.
WAAS holds a specific set of accuracy standards that ground station measurements must meet. Laterally and vertically, WAAS must be accurate to within 7. These ground stations send their measurements to master stations which send the corrections to WAAS satellites every 5 seconds or quicker. From the Satellite, a signal is broadcast back to the receivers on earth where the corrections are used to improve the GPS accuracy.
In some locations, WAAS is able to provide an accuracy of 1 meter lateral and 1. GPS data is displayed in different message formats over a serial interface. There are standard and non-standard proprietary message formats. The NMEA standard is formatted in lines of data called sentences. Each sentence contains various bits of data organized in comma delimited format i.
The data is separated by commas to make it easier to read and parse by computers and microcontrollers. This data is sent out on the serial port at an interval called the update rate.
Most receivers update this information once per second 1Hz , but more advanced receivers are capable multiple updates per second. Most GPS modules have a serial port , which makes them perfect to connect to a microcontroller or computer. Once a GPS module is powered, NMEA data or another message format is sent out of a serial transmit pin TX at a specific baud rate and update rate , even if there is no lock.
It is common for the microcontroller to parse the NMEA data. Parsing is simply removing the chunks of data from the NMEA sentence so the microcontroller can do something useful with the data.
Instead of dealing with all of this text, the microcontroller can parse the GPGGA sentence and end up with only the altitude in meters. Once the microcontroller can grab the data needed, the information can be manipulated to create other interactions on the microcontroller. Next, open a serial terminal program at the same baud rate of your GPS module.
The GPS chipset contains a powerful processor that is responsible for the user interface, all of the calculations, as well as analog circuitry for the antenna. The chipset also allows for data to be sent to the GPS receiver to configure parameters like, update rate, baud rate, sentence selection, etc.
In order to send commands over a serial interface to a GPS receiver, you will need a command set or reference manual. Navigation Project description Release history Download files. Project links Homepage Source Code Documentation. Statistics View statistics for this project via Libraries.
Meta License: Mozilla Public License 2. Maintainers bek3. This library is currently in Beta and is subject to change any time. Dependencies PySerial is the only dependency. See requirements. Usage See www. Examples Opening and Reading a Serial Port It is highly sugested that you use all input streams within a context manager with statement as shown below. See stackoverflow. It's for Windows — EM-D. Add a comment. Active Oldest Votes. Improve this answer.
Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.
0コメント