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Old 29-06-2015, 15:22   #1
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Canadian Charts waypoints move on pan

While entering a route I discovered that the waypoints moved when the chart is panned. These are Canadian BSB4 charts of Lake Ontario. It appears the chart boundaries are not properly registered in OpenCPN.

Two computers - Dell Vostro and Gateway Netbook, both Win 7, OpenCPN 4 Build 2015-05-08, BSB4 Plugin V1.2. Both exhibit the same problem on multiple charts.

To quantify the problem I moved a light to the 4 corners of the window. The Lat-Lon of the light changes with the window position. The chart moves about 25% faster/farther that the cursor. The waypoints and cursor move together. The distance and bearing from my boat location on the other side of the lake also changes as the chart is moved.

I have forced a rebuild of the chart database. No change. The BSB4 plugin has no Preferences. How do I correct this?

I have 4 screen prints for the effects but can't figure out how to attach them to the post.

Roger
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Old 29-06-2015, 18:28   #2
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Re: Canadian Charts waypoints move on pan

Bob re: screen prints
Choose "Go Advanced" and then click the paper-clip (symbolises "Attachments") beside the "" and you should be ok from there.
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Old 29-06-2015, 18:35   #3
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Re: Canadian Charts waypoints move on pan

Quote:
Originally Posted by HappySeagull View Post
Bob re: screen prints
Choose "Go Advanced" and then click the paper-clip (symbolises "Attachments") beside the "" and you should be ok from there.
He needs a few more posts to be allowed to post pictures...
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Old 29-06-2015, 18:38   #4
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Re: Canadian Charts waypoints move on pan

Trying to post the screen prints.
Click image for larger version

Name:	Can Chrt 1.jpg
Views:	61
Size:	212.2 KB
ID:	104414

Click image for larger version

Name:	Can Chrt 2.jpg
Views:	56
Size:	219.0 KB
ID:	104415

Click image for larger version

Name:	Can Chrt 3.jpg
Views:	57
Size:	205.7 KB
ID:	104416

Click image for larger version

Name:	Can Chrt 4.jpg
Views:	64
Size:	204.0 KB
ID:	104417

Roger
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Old 29-06-2015, 18:42   #5
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Re: Canadian Charts waypoints move on pan

If you look at the status line it shows the different Lat Long with the cursor on the base of the leading light (FR 33ft) each time. I also have the same area covered by the NOAA raster chart which doesn't have this problem.

Roger
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Old 29-06-2015, 22:27   #6
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Re: Canadian Charts waypoints move on pan

I have seen this problem a few times and it always boils down to that the charts are badly georeferenced. Do you get a warning from OpenCPN if you click on the chart down in the chart bar?

I don't know how to solve this for encrypted charts. Try to raise the problem with the people who sold you the chart.

/Thomas
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Old 30-06-2015, 07:59   #7
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Re: Canadian Charts waypoints move on pan

Aha.. You have a mixed bag of charts- not all new ones from the CHS? and including Polyconic charts. It's got to be hard to mesh different projections ....even for OCPN.

As I comprehend it, Polyconics were an especial way to make a harbour appear on the chart more naturally from the wheelhouse versus a mercator, so that landforms can look like they do in reality, versus Mercators that distort appearance more and more in higher latitudes . Lots of old surveys in North America used it, on small areas. But you can look it up yourself and see what conclusion the internet provides.

Meanwhile, an easy fix might be to investigate and create "Chart Groups" from the OpenCPN manual and group the Polyconics...

The problem of laying a sphere onto a flat surface has entertained generations of chart and map makers and still does. When these charts were surveyed these charts were made to print and to be used singly, on a table with a pencil. I think "quilting" (while not unkown) was not a requirement and still is not.

ADDed: just surmise, but if you have a chart covering a harbour, you want the whole chart to be accurate, including the edges where the approaches to the harbour may be. Perhaps a polyconic satisfies this, where a mercator does not.
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Old 30-06-2015, 08:27   #8
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Re: Canadian Charts waypoints move on pan

On further investigation I have 5 charts out of 27 on the CD that have this problem. They are all Polyconic. I have e-mailed CHS to see what can be done.

Roger
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Old 02-07-2015, 03:43   #9
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Re: Canadian Charts waypoints move on pan

Quote:
Originally Posted by HappySeagull View Post
Aha.. You have a mixed bag of charts- not all new ones from the CHS? and including Polyconic charts. It's got to be hard to mesh different projections ....even for OCPN.
as mentioned in the other thread, it's no problem for the projections branch
Quote:
As I comprehend it, Polyconics were an especial way to make a harbour appear on the chart more naturally from the wheelhouse versus a mercator, so that landforms can look like they do in reality, versus Mercators that distort appearance more and more in higher latitudes . Lots of old surveys in North America used it, on small areas. But you can look it up yourself and see what conclusion the internet provides.
transverse mercator are often used for the same reason.


Quote:
Originally Posted by RogerD View Post
On further investigation I have 5 charts out of 27 on the CD that have this problem. They are all Polyconic. I have e-mailed CHS to see what can be done.

Roger
I would say to try the projections branch as it fixes many issues with polyconics and quilting, however it is likely to break in some trivial and easy to fix way for BSB4 as I cannot use this plugin (windows only)
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Old 02-07-2015, 09:35   #10
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Re: Canadian Charts waypoints move on pan

Quote:
I would say to try the projections branch as it fixes many issues with polyconics and quilting, however it is likely to break in some trivial and easy to fix way for BSB4 as I cannot use this plugin (windows only)
Indeed, this is the way to go! Great work !

(Thread is here:

projections alpha test
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