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Old 13-02-2019, 12:23   #1
Marine Service Provider

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OpenCPN Weather Routing Plugin error

I'm running into a problem when I try to compute a weather routing using OpenCPN (ver 4.8.8) with prlugings Weather Routing (ver 1.0) and Grib (4.1).

I start and end the route in a body of water (Lake Michigan) well away from Land. I have the GSSGH high res maps install (and all other maps disabled).


The routing works for a few miles and than stops with error "Polar: Land: Error".


I would love to attach a zip file with the Grib file, the weatherroutingconfiguration.xml, Boat_J109.xml and polars file used. I can't figure out on how to attache a zip file. Forum doesn't seem to support zip files.


Any help / suggestions?

Thx Volker




weatherroutingconfiguration.xml
HTML Code:
<?xml version="1.0" encoding="utf-8" ?>
<OpenCPNWeatherRoutingConfiguration version="1.10" creator="Opencpn Weather Routing plugin">
    <Position Name="Start" Latitude="42.08300" Longitude="-87.43667" />
    <Position Name="Finish" Latitude="45.76850" Longitude="-85.81900" />
    <Configuration Start="Start" StartDate="2/13/2019" StartTime="2:07:00 PM" End="Finish" dt="3600" Boat="D:\My Documents\Google Drive\Sailing\Zigzag-269\Boat_J109.XML" Integrator="0" MaxDivertedCourse="90" MaxCourseAngle="180" MaxSearchAngle="120" MaxTrueWindKnots="30" MaxApparentWindKnots="30" MaxSwellMeters="20" MaxLatitude="90" TackingTime="0" WindVSCurrent="0" AvoidCycloneTracks="0" CycloneMonths="1" CycloneDays="0" UseGrib="1" ClimatologyType="4" AllowDataDeficient="0" WindStrength="1" DetectLand="1" DetectBoundary="0" Currents="0" InvertedRegions="0" Anchoring="0" FromDegree="0" ToDegree="180" ByDegrees="5" />
</OpenCPNWeatherRoutingConfiguration>




Boat_J109.xml
HTML Code:
<?xml version="1.0" encoding="utf-8" ?>
<OpenCPNWeatherRoutingBoat version="1.10" creator="Opencpn Weather Routing plugin">
    <Polar FileName="D:\My Documents\Google Drive\Sailing\Zigzag-269\J109-ZigZag_150Jib_120Spin.csv" CrossOverContours="C:\ProgramData\opencpn\plugins\weather_routing\contours\D:!?!My Documents!?!Google Drive!?!Sailing!?!Zigzag-269!?!J109-ZigZag_150Jib_120Spin.csv.contours" CrossOverPercentage="0" />
</OpenCPNWeatherRoutingBoat>
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Old 14-02-2019, 12:56   #2
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Re: OpenCPN Weather Routing Plugin error

Rename the zip file to .doc or .pdf and you will be able to attach it.
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Old 15-02-2019, 05:50   #3
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Re: OpenCPN Weather Routing Plugin error

please find attached all related files in Downloads.zip.pdf, a zip file that I renamed to *.pdf in order to allow the upload. Thanks Stelian for your tip.
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Old 15-02-2019, 05:52   #4
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Re: OpenCPN Weather Routing Plugin error

please find attached all related files in Downloads.zip.pdf, a zip file that I renamed to *.pdf in order to allow the upload. Thanks Stelian for your tip
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File Type: pdf Downloads.zip.pdf (376.2 KB, 8 views)
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Old 15-02-2019, 06:34   #5
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Re: OpenCPN Weather Routing Plugin error

This one is strange. I have reproduced the issue, and it looks like the route doesn't want to go across the 43th N parallel, as if is was some land there (but obviously it is not).


Looks like a bug.
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Old 15-02-2019, 14:32   #6
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Re: OpenCPN Weather Routing Plugin error

If I change the weather routing route Start from 42.083N to 43.083N then the program stops with the same error as above at 44N. Thus, same result. It won't cross into the next degree N.
Any help / thoughts on what is going on here?
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Old 15-02-2019, 15:59   #7
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Re: OpenCPN Weather Routing Plugin error

Quote:
Originally Posted by volkerpetersen View Post
If I change the weather routing route Start from 42.083N to 43.083N then the program stops with the same error as above at 44N. Thus, same result. It won't cross into the next degree N.
Any help / thoughts on what is going on here?
Likely a bug in land detection, it works if you disable detect land and use boundary.
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Old 17-02-2019, 08:47   #8
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Re: OpenCPN Weather Routing Plugin error

It looks like it only happens in inland waters.



I have isolated a test case, maybe this will help somebody to debug the issue:


gshhsCrossesLand(42.75, -86.50, 43.25, -87.50) returns true, but it obviously should return false...
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Old 17-02-2019, 13:03   #9
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Re: OpenCPN Weather Routing Plugin error

Ok, I dug through the code and finally found out that this behaviour is "normal".


Reading about GSHHG (GSHHG - A Global Self-consistent, Hierarchical, High-resolution Geography Database) shows that data is organised in several "levels", level 1 being "boundary between land and ocean, except Antarctica.", the other levels dealing with lakes, islands in lake, Antarctica etc.


And guess what ? Although all the levels are drawn on the screen, only the first level is considered for the "crossing earth" test (notice the usage of poly1 in src/gshhs.cpp around line 744.


So you cannot detect the land boundaries while in inland lakes (or Antarctica btw).


I'm not sure it would be useful to add this detection, and what would be the price performance wise.


But it sure is a surprising behaviour for the users !


Stelian.
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Old 17-02-2019, 14:43   #10
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Re: OpenCPN Weather Routing Plugin error

Stelian, good detection! Thank you.
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