Charts II: NGA - 2700 Charts

[phiggins]

nohal, cagney,

The reason I went with the cropping is that I would have to create a PWX and PWY statement which I believe is the upper left corner of the entire image and I don't know what the contents of all the fields (except first one, lat/lon). Perhaps you can tell me? So instead the chart created has PLYs for the area inside the cropped area.

I could put the information in the comments.

[nohal]

Paul,
have a look at https://github.com/ngacharts/ngachar...r-and-bsb-file
I don't think you have to care about PWX and PWY at all. All you have to do should be creating PLY/1-4 with lat and lon values for the 4 corners (clockwise from SW corner)
But we can recalculate it from your headers if you stay with cropping and put the coordinates to the header.
It would also be very (VERY) useful if you could require the user to calibrate all the 4 corners - not just it will improve the accuracy of the resulting KAP, but we will get a lot of useful info about the quality of the original image for the automatic part of our QA process.

Thanks

Pavel

[phiggins]

nohal, cagney,

You're right. Modified the GE2KAP and tried it without cropping and it works on OpenCPN with the quilt on (no borders shown) and with with quilt off and you see the border information. I was misinformed.

As for requiring calibrartion points at all 4 corners, I'd rather leave it as is with requiring one in the UR and LL where there are known coordinates and then putting in other points throughout the chart on known intersections of lat/lons.

Oh the reason I still need the UR and LL points is that I still need to crop it when I overlay on GE. If I don't overlay it on GE and just create the chart, I don't crop it.

[dacust]

If you have the PLYs, you should have the UR and LL (and UL and LR) already, unless it has cutouts. So, you just need to get your limits from the PLYs, not the REFs.

-dan

[Tia Bu]

Is there a combination of programs that will do both the calibration and the PNG to BSB conversion on a Linux machine? Have been noodling around trying to find a way, but so far struck out. Maybe I'm just missing the obvious?

Have made BSB's with Mapcal before (out of Google Earth captures, as I recall, back before PHiggins offered his program), but have since converted my machines to Ubuntu Linux. Would be glad to help with the calibration project if I could.

[phiggins]

Dan,

I don't have the PLYs, I generate them for the chart I create.

[Kudalufi]

It shouldn't be too hard to use Gimp and a fuzzy fill tool to smooth out the artifacts into a uniform colour. Moving to and from an indexed colour mode should also do the job. Make yourself a custom palette first that has all the colours you want, then convert the chart into an indexed mode using that palette. I'll take a shot at doing it when I get back from holidays (the WiFi at my camp site is really really poor)

[HappySeagull]

Originally Posted by Tia Bu

Is there a combination of programs that will do both the calibration and the PNG to BSB conversion on a Linux machine? Have been noodling around trying to find a way, but so far struck out. Maybe I'm just missing the obvious?

Have made BSB's with Mapcal before (out of Google Earth captures, as I recall, back before PHiggins offered his program), but have since converted my machines to Ubuntu Linux. Would be glad to help with the calibration project if I could.

...tried this?from the help file?Pretty much the same process.I'm Windosed but
Conversion Using Linux | Official OpenCPN Homepage
imgkap works on linux too,I think.
http://www.cruisersforum.com/forums/...tml#post686535 so on...

[Netsurfer]

David ...

Originally Posted by wdkester

But dacust says that another Opencpn guy (Netsurfer) wrote it. I was hopeing he would reply.

sorry for not answering, yet.
But I am actually very busy with the writing of the website for doing the chart calibration.

Additionally the KAP-File Utility was my very first attempt to write a VB.net application as a wrapper for the several command line utilities.
I also didn't plan to further develope this tool but instead write a new one based on the new imgkap script from MdJ.
But I guess it will be close to the end of the year before there will be a first alpha available ...

Gunther

[dpons]

Originally Posted by cagney

I'm working on the whole of region 2, Central & South America Caribbean etc.

I've done 24050 thru 24060 (Rio de la Plata kaps). 6MB average, where can I post them?

[NavPak ECS]

<< Moving to and from an indexed colour mode should also do the job. Make yourself a custom palette first that has all the colours you want, then convert the chart into an indexed mode using that palette.>>

Thanks Kudalufi for that excellent idea. I did this using Paintshop Pro (GIMP will work the same) and it works great. I saved a 16 color palette with white, black, 3 blues for the compass rose, shallow water, and shoals, and 2 greys for land. Most of the land is light grey and towns are dark grey. I picked these off the chart. Then I made the other colors red and saved the palette, but not the chart. Now you can use this palette over and over since the NGA charts all seem to be similar colors.

I can open an NGA image with 16 million colors (non-indexed palette), or change it to non-indexed, then load the custom 16 color palette and presto, it is ready for geo-referencing. The first thing to do is reduce the rez to 50%, then the custom palette will load quickly.

Reducing the colors like this will make the chart faster and more compact, and the night colors will look better.

[phiggins]

I made some modifications to GE2KAP so when it produces a chart calibrated with mapCal, it uses the MapCal border points to create the PLY entries in the chart. What is interesting about that is you don't necessarily need only 4 points. You can define more points so that you can eliminate portions of the original image.

For instance in the attachments the original chart 24402 has a subchart in the upperleft corner. But the view in OpenCPN with quilting on shows that it was removed because I defined the border to exclude it.

With quilting off you do see that excluded chart.

[nohal]

Paul,
could you please send me the KAP header for this chart? It's probably a very good specimen for some of our experiments

TIA

Pavel

[HappySeagull]

NGA 21301

tiff2bsb and MapCal can do this too.I didn't crop the plan out . I did have to make 2 kaps...

In this example,it seems to work best "bordering" from lower left first or MapCal get's confused.

PS works quilting on or off

[phiggins]

Pavel I sent the header.

HappySeaGull,

Well that is what I did, calibrate the chart with MAPCAL with the borders and then after saved it I ran GE2KAP that created the chart form the entry in CHARTCAL.DIR. GE2KAP calls TIF2BSB internally to create the chart.

Interesting that if I added more than 9 border points, TIF2BSB only puts in the first 9. Maybe charts can only have 9 or perhaps its a bug in TIF2BSB. Have you tried more than 9?