On Fri, 28 Feb 2014 09:41:29 -0500, Luke Szczepaniak wrote:

On 02/28/2014 9:28 AM, ES wrote:
Okay, things are starting to make a little more sense. On page 16
(section 5.1.2)there is a turnpoint name ("Line 11") above the course
direction indicator. When I saw that, I assumed I there was some task
storage and processing in the V7. If the task is not in the V7, where
does this turnpoint name come from? (From the Oudie, or from the
logger?)

The Oudie will have to send the active TP coordinates in an RMB sentence
back to the V7.

It must also be getting at least the WPL sentence and possibly is also
getting ROO sentences. I say this because the RMB sentence conveys the TP
coordinates but doesn't contain its name. Both ROO and WPL include the TP
name. WPL contains the name and coordinates of a TP: by comparing
coordinates between RMB and WPL the receiver can work out the RMB's
target TP name. ROO defines the task (in our terminology). All it
contains is a list of TP names in task declaration sequence.

The reception frequency differs depending on the sentence type. An RMC+RMB
pair are received every second with a third sentence appended. This
sentence is either an ROO or a WPL. The ROO and associated WPLs are sent
in a repeating sequence, one each second, so if you have 'n' turnpoints
in the active task, the sequence takes n+1 seconds to be sent.

I researched this some time ago when I wanted to understand why my SDI C4
wouldn't calculate wind unless the GPS it was attached to, a Garmin GPS
II+ at that stage, had at least one active waypoint. I ended up with the
Garmin plugged onto a PC and displaying each sentence as it arrived so I
could work out what was going on.


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martin@ | Martin Gregorie
gregorie. | Essex, UK
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