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Old 28-01-2015, 14:52   #1
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Chart Header Modification

I have loads of kap charts with an 'UNKNOWN' entry for the 'projection (PR=) type. Is there a method of just modifying the header data for the chart file? I need to change 'PR=UNKNOWN' into 'PR=MERCATOR' so that openCPN 4 will read the charts.

I have tried a simple text editor but it corrupts the data when the changes are saved.

Cheers. John
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Old 28-01-2015, 15:45   #2
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Re: Chart Header Modification

John...
Make sure the editor does not change the binary part of the chart (Notepad or wordpad on windows = not good, any other editor = most likely good)
After editing the header, you MUST fix the index table using bsbfix (If you are using Windows, get it from libbsb - Read, Write and Convert BSB charts, if you are using Linux, it is packaged in the Official OpenCPN PPA)

Pavel
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Old 28-01-2015, 19:11   #3
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Re: Chart Header Modification

actually O4 will open UNKNOWN charts.
See? (click the picture to see it better)

Click image for larger version

Name:	unknownchart.jpg
Views:	59
Size:	153.0 KB
ID:	96198

so try just bsbfix...and by the way, it seems to work fine (in XP anyways) to just drag the chart file onto bsbfix.exe...put a copy in your chart folder and try it...one at a time only this way.

You need be careful calling them MERCATOR alright because first off, it has more characters than UNKNOWN -8 vs 7 letters- and that will be an issue that I think bsbfix can fix , but you and WE are all better off without blithely copying mercator in if there's any chance you are going to share these charts.
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Old 28-01-2015, 23:04   #4
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Re: Chart Header Modification

I take your point on blithely adding Mercator but they are Mercator projection so it would be better to add it in if possible. I can't get O4 to open a kap chart that has an UNKNOWN projection. It will open a kap chart with an UNKNOWN datum as your example shows but I don't have a problem with the datum only the projection.
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Old 28-01-2015, 23:37   #5
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Re: Chart Header Modification

turtleback...
Missing projection is of course a critical issue. bsbfix will technically fix the charts you modify manually. If they still won't open, there is a critical issue with the calibration data and you can find the reason in the logfile. If it won't be clear, we need to have a look at one of them.

Pavel
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Old 29-01-2015, 10:53   #6
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Re: Chart Header Modification

ahSorry! inattention on my part.
But I did do the experiment by changing a chart to UNKNOWN in "notepad++" (losing a character! and I use ANSI because it seems native to the headers?...) ) and then change it back to MERCATOR , dragged it onto bsbfix and it worked....
I know a way to edit bunch at a time in freeware Notepad++ using the macro function or find+replace in ALL but there is probably a better way in some hexeditor capable of editing a bunch at a time so bsbfix might not be required but I haven't troubled to find it yet...
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