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Old 23-08-2012, 11:25   #16
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Re: Who is using OpenCPN on the Great Lakes?

I reprojected a few more charts, and checked around a bit more.
The program has two modes, a graphical- and a command-line- mode.
The graphical mode is dead simple.Infile + outfile + tell that you want a merc. That's all that is needed. As a side effect some valuable info is written to the console (if you start the graphical program from the command-line). This info, is more ore less what is required for a little 8 line txt file for each chart, to be able to re-project, without intervention, from the command-line. Add your favorite scripting language, as a "glue", and updating all the reprojected charts will become dead easy.

Nice little winter project for someone that yearns for all Mercator charts for the Great Lakes.

Thomas
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Old 23-08-2012, 22:49   #17
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Re: Who is using OpenCPN on the Great Lakes?

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Originally Posted by wdkester View Post
I just tried plan B: delete 14500, convert any mercators to poly, and use only the largest scale charts to create routes/WP etc or navigate in realtime (which is good practice anyway).

Unfortunately, the conversion routine outputs garbage for mercator to poly, I just get a black screen for the chart 14966_1. So back to ...
Don't you mean convert poly to merc?

Fabbian
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Old 24-08-2012, 06:32   #18
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Re: Who is using OpenCPN on the Great Lakes?

I have an older NOAA data set when the charts still covered the Canadian side of the Great Lakes. They are rasters. This is no longer the case as agreements with Canada who issues only propriatary charts now even though they are generated by tax dollars, so the newest set of NOAA charts only cover ports of entry on the Canadian side. I can donate these older charts if I had a place to upload them too for reference sake. They are from 2009. If interested let me know and yes they are legal as issued by the NOAA.

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Old 24-08-2012, 07:47   #19
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Re: Who is using OpenCPN on the Great Lakes?

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Don't you mean convert poly to merc?

Fabbian
Lake Superior only has 2 merc charts. I thought it would be easier to concert these 2 charts to poly than to convert the 30 or so poly to merc.

Dave's comment :

"I looked into this. It seems that some (all?) of the reference points in the repro chart are in error, badly. An artiact of the NOAA reprojection utility, I think."

scares me if we were to use the utility on large scale charts.
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Old 24-08-2012, 08:37   #20
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Re: Who is using OpenCPN on the Great Lakes?

David...

1. OpenCPN cannot use small scale Polyconics for quilting. I suggest that going from mercator to polyconic is the wrong direction for use of O. Better to convert the very few small scale polys to Mercator, then use O as normal in quilting mode.

2. The georef solution for reprojected 14500 is accurate enough for navigation at the charted scale. OpenCPN ignores internally detected bad ref points as it makes its best effort fit to a mercator projection.

Dave
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Old 24-08-2012, 09:31   #21
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Re: Who is using OpenCPN on the Great Lakes?

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Originally Posted by bdbcat View Post
David...

1. OpenCPN cannot use small scale Polyconics for quilting. I suggest that going from mercator to polyconic is the wrong direction for use of O. Better to convert the very few small scale polys to Mercator, then use O as normal in quilting mode.

2. The georef solution for reprojected 14500 is accurate enough for navigation at the charted scale. OpenCPN ignores internally detected bad ref points as it makes its best effort fit to a mercator projection.

Dave
This sounds sensible to me.

I think that polys of 120000 and larger scale can be used, There are only 2 polys of smaller scale than this 14500, 14860.

Don't we need a warning coming from Opencpn to 1. delete these charts or 2. replace these charts with the reprojected ones???

I'm not a script writer or I would volunteer to create a mercator version. But we still need a way to alert users to the problem.
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