Thread: GPS lag
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Posts: 529 | Thanked: 46 times | Joined on Sep 2007
#2
Originally Posted by ag2 View Post
In addition to all of the other problems reported with GPS, I think I found another one.

It appears that the gpsd daemon introduces a delay when reporting GPS data. As a result, mapping software (both maemo mapper and the built-in crappy one) show positions with a lag of a couple of seconds, sometimes more. This can translate into position inaccuracies of a couple hundred feet when driving at 70mph.

The reason I think the problem is in gpsd, is that there is a delay (as evidenced by NMEA timestamps) when running

/usr/libexec/navicore-gpsd-helper

but not when reading directly out of /dev/pgps.
It works exactly as you described.
Delay loop, introduced by navigation software is intended to save
low performance processor, performing graphics tasks at the same time.
Gpsd loop delay can be set to 1-2 and more sec.
Running gpsd as a terminal application you don't have to care for processor performance as mno graphics processoing (maps) is involved.

Darius