craporola

[sunilsk]

how often gps data is transmitted from satellite?

[shanks]

I don't know the technical specs of the GPS satellites - you'll find information about that elsewhere on the web, but if you are asking how often the GPS receiver reports its position then it depends on your GPS receiver unit. In my experience most of them seem to generate position reports with a period of 1 second. For instance, they send a NMEA GGA sentence each second once a fix is established. They usually output several different NMEA (or other format) variants of this information in that same time period.

I don't know how often the unit calculates and updates its position internally - may be a lot quicker and possibly some units have a proprietary communication interface that allows reading the data at a higher speed.

dr. matt.

[sunilsk]

Hi Dr. Matt,

Thanks for your kind interest.
Probably you were the only ones providing me the near appropriate reply.
I learn from your reply that GPS position reports is GPS receiver unit dependent.

As per observation in (my) GPSGO, every second the clock timer tickles, and understand that ~ every second data is updated!
and i agree to your point that "most of them seem to generate position reports with a period of 1 second"

However, i have browsed a lot of content on web and i could understand that :
1. GPS data is transmitted continually.
2. This data is formatted into 25 frames, each 1500 bits in length
3. These data frames are further divided into five equal sub frames.
4. Transmission of this data takes place at 50bits/sec, so at this rate
-it takes 6 seconds to transmit a sub-frame
-30 seconds to transmit a frame
-12.5 minutes to transmit the complete set of 25 frames.


the following links are the ones i referred to arrive at this reply:
http://www.radio-electronics.com/info/s ... ummary.php
http://www.colorado.edu/geography/gcraf ... gps_f.html

Kindly let me know if you come across further information.

thanking you