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Old 07-09-2012, 00:29   #1
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New Dashboard Instruments

Hi there,
we have a couple of new dashboard instruments now, implemeted in the current beta, so currently only available to source code builders.
Please see the attached screenshot.

For those guys with small displays and not much room for the graphical dial instruments, I created them as simple „text“ instruments. There are
  • Air Temperature (MTA sentence)
  • Magnetic Heading
  • Apparent Wind Angle (+- 180° on boat axis)
  • True Wind Angle (+- 180° on boat axis)
  • True Wind Speed
  • True Wind Direction
plus one graphical dial instrument for
  • True Wind Angle (+- 180° on boat axis)
Furthermore there are fixes for
  • True Wind Direction : it shows correct values now
  • ° character problem, at least in the "text" instruments (also in COG, Watertemp...) .
  • "Temp" is renamed to Watertemp now

The wind instruments have an automatic fallback from NMEA TrueWindAngle readings to MagneticWindAngle, if true is not available on the NMEA sentence. You see which one's used in the text based sentences as suffix mag/true

Please also note the wind direction indicators for "text" instruments :
> : wind from left/port side, e.g. > 236°
< : wind from right/starboard side e.g. 93° <

Except for the air temperature, which implements the MTA sentence, the instruments use the existing NMEA sentences.

Thomas
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Old 07-09-2012, 01:04   #2
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Is it possible that you in the setting for each instrument/parameter add the possibility to add a damping. This apply also to all existing instruments. I understand that the opinion among some of the program makers is that damping is not needed if a proper GPS/nmea-source is used, but we are a lot of users who have a HW-system already, experiencing problems, and at least my self does not know what to look for when buying a better GPS.
/Petter
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Old 07-09-2012, 10:32   #3
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Re: New dashboard instruments

So the damping you want is to prevent this spinning COG indication.
Maybe the damping could be implemented depending on SOG.
Something like SOG < 0.5 MPH = damping on, else off.
(I have no clue about how to do this).
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Old 07-09-2012, 13:18   #4
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My proposal: A calibrate/setting value for a time factor. The time factor is how often the instrument shall update. The value shown is the average of the values recorded since the last update. Maybe not the best solution, but anyone understand the function.
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Old 07-09-2012, 13:33   #5
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Re: New Dashboard Instruments

Quote:
Originally Posted by pa36651 View Post
My proposal: A calibrate/setting value for a time factor. The time factor is how often the instrument shall update. The value shown is the average of the values recorded since the last update. Maybe not the best solution, but anyone understand the function.
Simple damping might be as simple as a limit on how much value change can happen between display updates.

True damping is like "inertia" - the pointer has a mass, and the rate of change is a force applied to the mass, and the force is proportional to the amount of change being called for.
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Old 09-09-2012, 01:10   #6
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I still think it is a problem that the values dependant on the GPS are changing to often and to much when using instruments with figures.
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Old 09-09-2012, 10:26   #7
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Re: New Dashboard Instruments

For NavMonPc I implemented simple "linear boxcar filter" damping for all parameters where damping might be desired. The amount (speed) of the damping can be varied by the user from none to (as I recall) ten seconds of data. The boxcar filter simply takes the average of the previous "n" seconds of data, where "n" is an integer between 0 and 10. I run a one-second sample rate. There are simpler, and more complicated, filters, but I found that the boxcar was fairly effective.

Probably the simplest digital filter is the "single pole IIR" design (look it up). It works OK, but for even a small amount of filtering it does take a long time to reach its final value.

For filtering of COG or other "modulo 360" data you will need to do your filtering so (for example) a shift between 350 and 010 doesn't average out to 180. I do this by looking at the direction and amount of change between samples, and adding or subtracting to compensate. I would be happy to describe the simple algorithm if anyone is interested.
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