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Global Positioning Systems *

GPS, GLONASS and other systems

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Does GPS transmit different data into LNAV and CNAV messages?

Global Positioning Systems *Development of communication systems *

Different navigation message protocols are used for different navigation signal type. This is true even for a single system like NAVSTAR GPS. For example, L1C/A signals have a LNAV protocol, while L2C and L5 signals utilize a CNAV protocol. The newest L1C signal will use CNAV-2. 

The protocol defines a data distribution into frames, subframes, the subframes structure, transmission intervals, data resolution and so on. 

A navigation receiver use the navigation message data flow for several purposes:

1. The data flow allows to resolve a code ambiguity and set the signal time.

2. Ephemeris and clock values are used for the satellite position calculation, pseudorange corrections and coordinates computation.

3. The received data flow and navigation message data can be used for navigation symbols prediction. As result, we can use the wipe-off technique, expand discriminators and significantly increase tracking sensitivity:

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MEMS accelerometers, magnetometers and orientation angles

Global Positioning Systems *Algorithms *Mathematics *Robotics

When it's necessary to evaluate the orientation angles of an object you may have the question — which MEMS sensor to choose. Sensors manufacturers provide a great amount of different parameters and it may be hard to understand if the sensor fit your needs.

Brief: this article is the description of the Octave/Matlab script which allows to estimate the orientation angles evaluation errors, derived from MEMS accelerometers and magnetometers measurements. The input data for the script are datasheet parameters for the sensors. Article can be useful for those who start using MEMS sensors in their devices. You can find the project on GitHub.
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