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Old 06-03-2013, 07:36   #1
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Tracking Precision

Are the only precision choices High, Medium, Low?
Are all three time interval choices? (I am stuck at my desk and cannot try it out for myself)
Is there any way of setting precision by distance - I thought there used to be?
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Old 06-03-2013, 12:24   #2
bcn
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Re: Tracking Precision

No, it is not just the sampling rate. It's more advanced.

Please have a look at the manual (in OpenCPN the "?" icon and there the "help" tab) regarding tracks and "ownship"

bcn
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Old 06-03-2013, 12:49   #3
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Re: Tracking Precision

Thanks bcn. All I see on my version 3.2.0 is High, Medium, Low. In what way is it more advanced....how may I find out?
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Old 06-03-2013, 12:54   #4
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Re: Tracking Precision

Quote:
Originally Posted by bcn View Post
Please have a look at the manual (in OpenCPN the "?" icon and there the "help" tab) regarding tracks and "ownship"

bcn
OpenCPN has really a very good and complete manual !!

Please, please, please read it: it's for you
and studying it you might discover a lot of goodies
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Old 06-03-2013, 13:14   #5
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Re: Tracking Precision

I entirely agree it is a superb manual. And I have indeed read much of it. And found many goodies. But sadly not the answer to my question
John
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Old 06-03-2013, 13:24   #6
bcn
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Re: Tracking Precision

From the manual:
----------------------------------------------
Tracking Precision

With track button in the ToolBar activated this setting affects the size of the data saved. It also affects the "smoothness" of the track, though this is only visible when zoomed in to a very large scale.
OpenCPN uses smart dynamic tracking, and only uses those track points that actually contributes anything to the track. A straight line track for example is only represented by it's endpoints. This is done by analyzing the track just behind the boat. The process is visible in real time, close to "ownship". The end result is good track accuracy while keeping the size small.
Low: Good for offshore passages.
Medium: Very good for all normal uses.
High: Only necessary when very tight maneuvering needs documenting.
----------------------------------------------

Somewhere in the forum there is some more material about the smoothing algorithm IIRC

The other alternatives to know more details about the optimization:
- asking the author of the tracking
- having a look into the sources
- or somebody else can shed details
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Old 06-03-2013, 15:25   #7
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Re: Tracking Precision

Quote:
Originally Posted by Bluesipp View Post
Are the only precision choices High, Medium, Low?
Are all three time interval choices? (I am stuck at my desk and cannot try it out for myself)
Is there any way of setting precision by distance - I thought there used to be?
The new tracking is way smart. Run a route by using the VDR with tracking on, and using the different settings. Zoom in and you will see the feature at work, in real time, behind the boat, as the tracking algorithm is selecting and rejecting track points. Only points contributing to the track are allowed. If you want to see the nitty griitty code of the details have a look at navutil.cpp line 2285.

The old pure time- or distance- based options lead to huge track files, with unnecessary track points. Think time-based track, when not moving, or distance based when the track is a straight line.

I tested this feature quite a lot when JesperWe developed the whole thing, and became convinced that it does work. Using the high setting you will get a a much better track than you, probably, ever need and a small size footprint when saving the track.

The simple interface hides a very smart feature.

But as I said, test it yourself with VDR.

Thomas
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Old 06-03-2013, 20:53   #8
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Re: Tracking Precision

Thank you both very much indeed. That solves all my problems. And bcn I still haven't found that in the manual, but I will try harder! Thanks again.
John
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Old 06-03-2013, 21:11   #9
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Re: Tracking Precision

Sorry, sorry - now I've found it. Blind and stupid.
John
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Old 07-03-2013, 07:42   #10
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Re: Tracking Precision

Phil Higgins had a good idea for loading the Google Earth Cache. When the way points were at a certain distance he would fly over the route at a certain altitude. When the way points were closer he would fly at a lower altitude. For an auto precision mode the same idea could be used with tracks eg. >10nm (between WP) = low, 1-10 nm = med, <1nm = high. Perhaps another case of "gilding the lily" , but I can imagine that when I come to a tight spot I probably won't remember to set the precision = high.
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Old 07-03-2013, 20:06   #11
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Re: Tracking Precision

Many thanks David. I will send a pm.
John
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