mbtiles in opencpn

[seandepagnier]

I have some success with two basic scripts I have written to put tiled data into opencpn. There are many tiled data available via the web such as osm, google earth, topographic data etc.. If you have used sas planet you can see quite a list of sources.

The first script extracts the coordinates of all of the cm93 tiles into a seed yaml file. mapproxy-seed pulls the tiled data into an mbtiles file with worldwide coverage and good scale without running out of storage, and with reasonable bandwidth. I realize this has limitations as cm93 doesn't cover a lot of areas with good detail, but it's a starting point and covers a large amount of harbors and difficult passes. It's easily possible to add additional coordinates as needed in the future to expand the database.

Making mbtiles a native format in opencpn is a goal of mine, but in the meantime I wrote another script which converts this single mbtiles file into thousands of kap files.

The results are very good initially and there are various minor improvements to make.

I can for example pull google imagery, In fact the current ge2kap which by comparison is not as user friendly (mine can work on any os and just needs an input of bounding boxes, contours or shapefiles to define the areas to scan)

But there is a pressing issue. I know on many sail blogs etc, you can download google imagery kap files. At least, it is ok for a single user to pull but according to google, it is a violation of their tos to redistribute imagery.

Furthermore I would apply various filters to the imagery especially to improve contrast over water, and possibly to reduce detail over land to save disk space.

[rgleason]

Looks like Sean found a helper program and is contributing.
https://github.com/seandepagnier/landez

[deepthought]

@boat_alexandra: Anything we can see or playwith? Are your scripts on github or possilbe to try?

Thanks

[sailorF54]

I already have mbtiles extracted from some SASPlanet maps/charts.
I hope to be able to use them in OpenCpn in the near future, just as I already can in qtVlm...

[seandepagnier]

You can use the scripts on github to convert mbtiles into kap.

[sailorF54]

Originally Posted by boat_alexandra

You can use the scripts on github to convert mbtiles into kap.

Yes I personally could, but I was thinking of the 99% for which Linux is a foreign language, as opposed to W...

[seandepagnier]

The scripts should work on many os

[ploubaz22]

i try to convert mbtiles to KAP for use with open cpn but the convert files kap was very very big compared file format mbtiles
Some software like saigrib can read directly file mbtiles

[seandepagnier]

How much bigger?

mbtiles uses png compression which could be half the size of kap. If you have mbtiles using jpg, let me know.

You can compress the kap using xz which gets it back down to nearly the size of mbtiles again, and opencpn can read that.

I cannot find the source code to "sailgrib" so it's impossible for me to even run the program, it can't run on my platform.

[deepthought]

Would be nice to make script that can convert raster to vector charts

[transmitterdan]

Originally Posted by deepthought

Would be nice to make script that can convert raster to vector charts

If I had a computer program that could do that I would own the largest yacht in the world.

[deepthought]

I think its possible...

[transmitterdan]

Originally Posted by deepthought

I think its possible...

Then the world will be your oyster when you do it. There are companies that convert raster technical drawings (architectural, electrical schematic, etc.) to vector. They charge a lot for each drawing as it requires significant human intervention because up to now there is no perfect software that can do it. Raster charts are about 100 times more complex than architectural drawings.

[rgleason]

We can always hope that AI +AI see Mit technology this month and Quantum computing will do it smile.

[rgleason]

Sean, since png files cannot be compressed as efficiently as jpeg (even considering they are lossey), what about adding to the mbtile spec, the use of jpeg?
Maybe some small program that converts png2jpeg and swaps the image data?

I like your description of what your scripts do. I hope Jon Turgeon venturefarther.com could incorporate that into his server as an efficient scheme, somehow.