Home made chart not visible

[bejo52]

Hi all,
untill now I used NV or ENC charts and every thing worked fine.
But now I try to create a chart from a scanned map according the chart creation manual.
I used MapCal2 for the calibration of a png file, mc2bsbh to create header file and Imgkap to create the kap file. Every thing worked without error
When I open OCPN I see the pink outline of the chart in the world map with I beleave the right orientation. Zooming in the chart pops up with a straigt north orientation (wrong) and now the chart can not be zoomed in or out anymore and is fixed to the upper left corner. I attache the haeder file (the kap file is 15 MB) with the hope some one can recognise any error I made.

Thanks in advance
Joerg

[cagney]

The log opencpn.log will contain info about your chart.
You cannot expect OpenCPN 3* to show a chart that has no projection.

PR=UNKNOWN,PP=UNKNOWN

It's best to supply both these values.

Thomas

[bejo52]

Hello Thomas,
thank you for the hint.
I added the mercator projection to the map. For the PP parameter I searched in the web which value I have to use but I could not find a clear explanation so I left it unknown.
The result looks different but not OK. See the attached picture.

Joerg

[HappySeagull]

excellent explanation of the kap "header" is here:
imgkap | Official OpenCPN Homepage

it looks to me like something is wrong with the calibration. I would check this out, and re-make the chart.

[bejo52]

the good things are so near and I didn't see it ;-) OK I added the PP value, nothing changed.
I referenced a new chart, the same result.
I used the calculated corner points as reference points, no change.
I even referenced the chart with oziexplorer (for street maps it allways worked) and converted it with map2kap.rb but even this give me the same result.

In the opencpn.log file I can only find this which is related to this chart:
19:21:07: Searching directory: D:\Karten\Seekarten\Shannon for *.kap
19:21:07: Loading chart data for D:\Karten\Seekarten\Shannon\shannon1_1.kap
19:21:07: Searching directory: D:\Karten\Seekarten\Shannon for *.geo
19:21:07: Searching directory: D:\Karten\Seekarten\Shannon for *.000
19:21:07: Searching directory: D:\Karten\Seekarten\Shannon for *.s57
19:21:07: Searching directory: D:\Karten\Seekarten\Shannon for 00300000.a
19:21:07: Searching directory: D:\Karten\Seekarten\Shannon for *.EAP
19:21:07: Finished chart database Update
19:21:07:
19:21:07: Chart cache purge
19:21:07: Initializing Chart D:\Karten\Seekarten\Shannon\shannon1_1.kap
19:21:12: VP Endkontrolle: Georeferenzierung Fehlerfaktor für die Karte D:\Karten\Seekarten\Shannon\shannon1_1.kap is 0.0291393

The last sentence appeared only one time.
I am helpless what to try else.

Joerg

[cagney]

A correct PP value would not make any difference in this case, if ....it is a Mercator map.
The last sentence in the log, is OpenCPNs way of saying that the calibration is crap. Somehow you have entered wrong values.
I can find the Shannon map on line, but as far as I can see, there are no positions on the map. So, presumably you have those from other sources. Check? What says that this is a Mercator map at all? Check?
The only way to have full control of what's going on is to manually edit the header file, to make sure the values are correct. All the tools you are using are just there to hide the (ugly) reality

Looking a bit more at your PLY points, it appears that the map is skewed. Still the SK value is 0. The SK value must contain the number of degrees that the chart deviates from North. If the map is lined up N/S, well then, check your PLY points!

Thomas

[HappySeagull]

...exactly.(as Cagney says) If it's not SKEW missing, and the map is supposed to display as a plain North-up Mercator rectangle, your corners should "agree"-that is, upper corner latitudes are the same,
lower corner latitudes are the same,
left side longitudes are the same
right side longitudes are the same .
They will "agree" to decimal points depending on the scale of the map!
or nearly so. Yours do not appear to be so.

[bejo52]

I checked the reference points again and I can not find a mistake. The chart is definitely not 'North-up'. The shown outline of the chart seems to bee at the right location and right orientation and the corner points are calculated by the reference points. Only the content (the picture) doesn't follow the orientation. Whether it is Mercator I guess (there is no description at the chart). But when I put the chart as a layer on top of OSM, turn it and scale it but not distort it, it fits with the OSMap and this is Mercator. Is OCPN not able to handle turned charts? But the NV-charts also not north-up. Joerg

[cagney]

Originally Posted by bejo52

I checked the reference points again and I can not find a mistake. The chart is definitely not 'North-up'. The shown outline of the chart seems to bee at the right location and right orientation and the corner points are calculated by the reference points. Only the content (the picture) doesn't follow the orientation. Whether it is Mercator I guess (there is no description at the chart). But when I put the chart as a layer on top of OSM, turn it and scale it but not distort it, it fits with the OSMap and this is Mercator. Is OCPN not able to handle turned charts? But the NV-charts also not north-up. Joerg

If the chart is skewed, you must set the correct value for SK in the header. Your value SK=0 indicates that the chart is not skewed.
OpenCPN have no problems with skewed charts. Download some NOAA raster charts for, say Florida, and you will find many skewed charts along the Intracostal Waterway. Just one example



This is chart 11948-2 shown in North Up, Single Chart, Mode.
The skew angle in the header for this chart is

SK=74.4519444

Thomas

[HappySeagull]

without the image, I can only guess at what's going on at your end and therefore I'm looking for clues in what you say, Joerg.

.... but from the above "(I)..turn it and scale it ... it fits with the OSMap and this is Mercator" , then it seems obvious that you should turn it in an image editor FIRST to agree with a North up orientation, save the new image and only THEN calibrate it.
O will have nice, Mercator corners to place in the quilt! The actual borders should then hide fine when quilting on.

O can handle skewed charts but at the extremes, it's much better to fit the chart to a Mercator template yourself. You will save O much work- why should she be forced to turn your homemade chart everytime when you yourself cannot trouble to do it once yourself?

and, did you see
post #6...SKEW = "turned" .

Also, try turning quilting off, when investigating a problem chart.

[HappySeagull]

oh, Hi, Thomas!
anyways, there's two approaches for you, Joerg!

[bejo52]

Thank you all together.
The angle value in the SK parameter was the essential hint. Now it works.
It's only a little difficult to calculate it but I will get it.

Joerg

[HappySeagull]

That's good news. Joerg, but be aware that quilting skewed charts can be problematic. You may need to turn quilting off.
I had several official skewed charts and found it suited me to deconstruct, turn the picture, and reconstruct as kaps. A tip for that is to turn "smoothing" off....

[HappySeagull]

...turn smoothing off in the image-editor when you turn the image to unskew it, is what I mean !