bugGPSD - Bugs: bug #49175, AIS AIVDM data not correctly...

 
 

bug #49175: AIS AIVDM data not correctly decoded

Submitted by:  Andreas Bals <abad>
Submitted on:  Sat 24 Sep 2016 03:38:02 PM UTC  
Votes:  2  
 
Category:  None Severity:  3 - Normal
Item Group:  None Status:  Invalid
Privacy:  Public Assigned to:  None
Open/Closed:  Closed

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Wed 26 Dec 2018 02:41:24 PM UTC, comment #2:

Two years old, no reason to believe the bug is real, some reason in our test loads to believe it is not, user never responded to Gary's question.

I'm going to call this operator error and close it. If it;s still a real error abad can reopen.

Eric S. Raymond <esr>
Project Administrator
Wed 06 Sep 2017 01:44:00 AM UTC, comment #1:

Andreas, please review the three divisors at gps.h line 898, and the code at gpsd_json.c around line 1628. It appears to be doing the exact division you specify.

Are you lookig at some output other than JSON?

Eric S. Raymond <esr>
Project Administrator
Sat 24 Sep 2016 03:38:02 PM UTC, original submission:

Input string:

!AIVDM,1,1,,A,139oP?TP00PPn5VM0LpN4?wb2D0h,0*2B

GPSD tranlates it nearly correctly into:
211673150, -, 30416097, 4305075, 3600, 511, 0, -128, , 1
(MMSI, imo, lat, lon, couse, heading, speed, turn, callsign, type)

Unfortunately one processing step on lon/lat is missing.
AIVD-lon/lat is given in minutes * 10'000.

In order to get location in degrees you have to divide by (10'000 * 60):
30416097/(600'000) = 50.693495 deg lat
4305075/(600'000) = 7.175125 deg lon

Andreas Bals <abad>

 

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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2018-12-26 esr StatusNone => Invalid
        Open/ClosedOpen => Closed
    2016-09-26 abad Carbon-Copy- => Added abad

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