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8/22/2017 2:56 pm  #1


Comparing 2 tracks and Stripchart

When comparing more than one track, ideally having Stripchart open for both enables proper analysis and understanding.  It would be great to open a second Stripchart and toggle between them and the tracks.

 

9/17/2017 3:40 am  #2


Re: Comparing 2 tracks and Stripchart

Let me take this one step further.  If I have two nearly identical yachts, and both their tracks, and the tracks are contemporaneous, how to easily compare data across the two?  If (for example), I want to compare TWS and TWA for instrument checking purposes, the easiest way I can think of to do it is to load both tracks in Expedition, two simultaneous stripcharts, and compare short time samples.  But I can't display TWS on tracks (visual comparison), and can't load two simultaneous stripcharts for side-by-side comparison using wands.
More than happy to hear how others might do it.
And yesterday the A4 failed in 36 knots TWS at 20-something knots BSP, everybody squeezing together on the pushpit, bow invisible under water.  We think the top end of the A4 might be a tad less than that 36 knots.
Cheers

     Thread Starter
 

9/17/2017 9:24 am  #3


Re: Comparing 2 tracks and Stripchart

if you have 2 log files (e.g. from different boats) for which you want to compare e.g. TWS or TWA,   what you could do is the following:
Open both log files in Excel and in one of the Excel files you replace the columns that Expedition has logged for AWS and AWA with the data of TWS and TWA of the other log file.    When you then save the file as CSV again you will be able to compare the TWS/TWA of the two boats by creating a Stripchart that displays TWS, TWA, AWS and AWA,  knowing that un fact the AWS/AWA traces are the TWS/TWA of the other boat.

However, be careful that the data line of the two log files are synced in time when you insert the data.   Ensure both log files have the same logging frequency (e.g. 1 Hz) and that you then copy the correct lines so you indeed compare data from the same moment in time.

 

9/17/2017 11:50 am  #4


Re: Comparing 2 tracks and Stripchart

As an extension of this idea

​1. Open both in Excel.
1. Change the boat id (the first field) to say 1 in the second file.
2. Cut and paste the data from this to the end of the first file data.
3. Sort the Excel file by the DATE field,
​4. Save with a different file name so you don't over-write the existing log file(s).

​Now you will have a log file with all the data merged.

 

 

9/17/2017 12:19 pm  #5


Re: Comparing 2 tracks and Stripchart

That's indeed a much better and simpler way of doing it Nick!   

 

9/17/2017 5:13 pm  #6


Re: Comparing 2 tracks and Stripchart

Nick
I take your thinking is to do an Excel PVT analysis rater than try and bring it into Expedition somehow?

     Thread Starter
 

9/17/2017 7:55 pm  #7


Re: Comparing 2 tracks and Stripchart

The above suggestion was for reading into Exp, Stripchart etc.

 

9/17/2017 9:48 pm  #8


Re: Comparing 2 tracks and Stripchart

Hmm, I just tried that, the two logfiles combined into one logfile, two different boat numbers, 0 and 1.  From your comments above I was expecting to see two tracks in Expedition, and two graphs in Stripchart for each variable .... but I dont see that, only one track, one set of variables in Stripchart.  What am I missing?
And Zee and Nick, thanks for your input.  This site is a great thing .

     Thread Starter
 

9/17/2017 10:41 pm  #9


Re: Comparing 2 tracks and Stripchart

Duncan,
Afaik you can only display 1 track.
However, in stripchart you can indicate for which boat you want to see each variable for which you display a chart.  So you can e.g. make a chart displaying TWA for boat 0 and TWA for boat 1.  When you then set wands you can compare the two TWA's.



 

 

9/17/2017 10:51 pm  #10


Re: Comparing 2 tracks and Stripchart

Zee, you can display 2 tracks, that I know.  Just load up a second logfile and do not erase the first, all OK.  What I was assuming is that when combining files as Nick suggested, you would be able to see both simultaneously.  And then, loading the combined file into Stripchart would let one see for example TWAs or TWSs.  Clearly not.  From your last post, you suggest I can do something like that, but I am not sure how.   You cannot load two logfiles in Stripchart?  Or do you open a second copy of Stripchart loaded with the second logfile?

     Thread Starter
 

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