OpenSeaMap - S57-Based

[sinbad7]

Hi Jonas..

This is the URL for the Norwegian Coast Guard :

Just take a screendump of the full screen chart after configurating the area you need. and then calibrate/convert to .kap

I actually grew up in Kristiansand and for several years until 2003 I was running a yacht charter service for business groups with my belowed 60' MS Eight Bells.

[arnand01]

Hi Tore/Jonas,
There is one alternative to screendump, you can try "Eksport til geojpeg" (see attatchment). The download produced contains both raster and a jpeg World-file.

/Anders

[sinbad7]

Kystverket site
Hi Tore/Jonas,
There is one alternative to screendump, you can try "Eksport til geojpeg" (see attatchment). The download produced contains both raster and a jpeg World-file.

/Anders

Yes I saw that option as well and it would be great if the .jpg World calibration file could be used to produce the .kap file. Would this be possible?

[tfickett]

Just as aside, the Open Sea Map project uses OpenStreetMap for it's data store. IIRC it also renders with mapnik (OSM's) renderer. Why couldn't OpenCPN integrate mapnik? Then you've got access to all of the OSM data, streets included. I've not evaluated what it takes to work on mapnik but I do contribute to mapping on the street side of OSM.

Forgot:
http://wiki.openstreetmap.org/wiki/OpenSeaMap

[sinbad7]

Hi all..

Until someone with the skills and motivation to check out the
possibility to incorporate WMS or similar into OpenCPN we are
not going to make significant headway.

As there does not seem to be much interest in the development of
Open Source charting facilities,I will belay my sails until more
favourable winds will blow.

Thanks to those who gave support..

[sinbad7]

Large area maps are now being produced by OpenSeaMap for download.
Very useful for planning and grib weather forecasts. Major lights and sea marks will be added at a later date.

1. The German/Danish North Sea
2. The Mediterranean
3. The Mexico Gulf
4. The Caribbean

Download here:

[antonm]

Originally Posted by sinbad7

motivation to check out the
possibility to incorporate WMS or similar into OpenCPN we are not going to make significant headway.

Since I am a kind of a programmer myself and recently did review of Open GIS technologies for my hobby tracker project, I would like to post here a clarification based on my current understanding of the subject.

1) Norwegian Coast Guard does not look like to be using OpenSeaMap, they are using OpenLayers (OpenLayers: Home) - a free and open JavaScript library to display map on web page with support of lots of different features. It is open alternative to similar widget that is provided by Google and it can be used by anybody who wants to display a map on the site or have something even more complex like tracks or markers display. This library is used by OpenStreetMap and OpenSeaMap to display their maps (well it's a kind of collaborative development and people contributed to both projects, but OpenLayers in no way specific to one particular implementation and it is designed to be this way). OpenLayers is for web sites and written in JavaScript, so most likely no use for OpenCPN.

2) WMS is OpenGIS Consortium standard for servicing georeferenced images (raster map tiles) over the internet. If one need to deliver raster map, he can use WMS protocol for it. Any tool that supports this protocol will be able to display this map using known WMS server URL. Looks like Norwegian Coast Guard created their own WMS server that serves tiles of their maps, it's seen in the page source. Since OpenLayers supports WMS, they are using it to display maps from their server. It's pretty common, for example NASA has WMS service serving their aerial photo tiles. If WMS protocol support is implemented in OpenCPN, it will be able to display georeferenced image (raster map, photo or whatever) from any network accessible WMS service. When boating in areas with no network connection, this feature will require some pre-caching of maps. AFAIK WMS is for raster images only, but it is not always bad.

3) OpenStreetMap is not just the map. Map is just most visible part of it. OpenStreetMap is a set of tools, standards and infrastructure to collaboratively work on arbitrary set of geo data. Simply speaking any data that can be presented in XML format can be stored in OpenStreetMap database (of cause there are technical limitations and requirements here). The question of is this data will be visible as the map or can be edited by given tool depends on those particular tools support of this schema. There is no requirements on how things are tagged in the database XML, but people tend to come to mutual agreement of how to tag specific things they need within the knowledge domain they need and then develop tools that understand this agreed tagging scheme and turn this into something more useful than just XML markup.

For example OpenStreetMap (the map itself) is several tools that generate the map from this XML based on the tagging scheme agreed. This tagging scheme is coordinated via wiki at this case and the resulted map based on this scheme is finally displayed on OpenStreetMap.

But it is not possible to display anything on one map, so there is other groups of people that want to display something for their tagging scheme and their set of tags, such projects produce things like OpenSeaMap or OpenCycleMap that use different configuration of rendering to produce the map the way they need it. But the data comes from "big single XML" database that is common for all and particular things may not be displayed on OpenStreetMap site, because it is tuned to other tag set, some features of cause can be and are common. It's up to people to choose what and how is displayed.

To make such things easy, OpenStreetMap has special API service to work with this common "big XML" database. Tool talks to this API when it need to add some data to this common datasource or generate map out of it, etc. So those are things like creating XMLs and sending it in or generating something useful from the XMLs that come out. Than more similar to exisiting tagging schema is used than it's easy to reuse the existing software.

It's getting long enough, so, I am stopping here. Hope it's useful.

[sinbad7]

antonm..

WOWWW!!! Thanks for a very in-depth explanation..

The bottom line, is OpenSeaMap or OpenStreetMap suitable for use with OpenCPN without having to do a major task of re-programing?

What other FREE and open mapping source is available for conversion to a nautical map readable by OpenCPN?

Thanks again..

Tore

[antonm]

Originally Posted by sinbad7

The bottom line, is OpenSeaMap or OpenStreetMap suitable for use with OpenCPN without having to do a major task of re-programing?

At the moment I am not that proficient in OpenCPN internals and marine standards, but here are my thoughts:

- The question of how easy to convert OpenStreetMap XML to already supported S57 is open.
- There is Osmarender available that is actally a set of XLS transformation files to convert OpenStreetMap XML into SVG. This transformation can be done by any xslt processor and there are open source versions of cause. But, OpenCPN does not support SVG, I believe there are open source libraries available to read it and may be used.
- Pre-caching mechanism will have to be developed either in OpenCPN or as a stand alone tool otherwise those data will be availble only when network connection is available.
- Also UI to get/post data is also needed and today I realized that if we stick with OpenStreetMap than the data user submit using those tools will be bound by open source license. This may or may not be a problem. However, this does not mean that we cannot use OpenStreetMap tools. It is possible to use OpenStreetMap XML format as internal one and then either post it directly to OpenStreetMap or convert to some other format for some other system depending on user's choise. The idea here is that even if we decide to go with different services support we still can elaborate the format and tools for our use instead of designing from scratch.

Originally Posted by sinbad7

What other FREE and open mapping source is available for conversion to a nautical map readable by OpenCPN?

Someone need to list that.

[zenfunk]

Hi, I'm Christian.
I'm involved with Openstreetmap for almost 2 years now. Being also a sailor, I started adding nautical features to OSM for about half a year or so. Though being a hobbyist in the field of maps, I hope to clear up some things.

Originally Posted by antonm

At the moment I am not that proficient in OpenCPN internals and marine standards, but here are my thoughts:

- The question of how easy to convert OpenStreetMap XML to already supported S57 is open.

It is my understanding that this is exactly what is worked on by the OSeaM project. They currently develop a OSM xml tagging scheme that is somewhat as feature rich as S57. Converting that to S57 shouldn't be a problem then.

- There is Osmarender available that is actally a set of XLS transformation files to convert OpenStreetMap XML into SVG. This transformation can be done by any xslt processor and there are open source versions of cause. But, OpenCPN does not support SVG, I believe there are open source libraries available to read it and may be used.

I don't think that we should need the workaround via svg- better convert OSM data to S57 which is a somewhat native format for OpenCPN. It completely eludes me how this is to be done (I'm neither a programmer nor maths wiz...), but from what I gather from the OSM wiki about their data structure, it seems doable (I could be completely wrong though). Anybody here that is willing to write a osm2s57 proggie?
Another way could be to add support of OSM files directly and render them on the fly. The OSM files for nautical use could be stripped of all the non essential information like Wyoming, Mongolia, Central African Republic, shops, reastaurants and whatnot, so the datafile could be very small.

- Pre-caching mechanism will have to be developed either in OpenCPN or as a stand alone tool otherwise those data will be availble only when network connection is available.

What I really would like for OSeaM is a worldwide datadump. If you ommit the data further inland, I think the filesize should be comparable to the c- maps- something like 2 cd- roms. Especially on the water, beeing online isn't very easy to do reliably and cost effective.

- Also UI to get/post data is also needed and today I realized that if we stick with OpenStreetMap than the data user submit using those tools will be bound by open source license. This may or may not be a problem. However, this does not mean that we cannot use OpenStreetMap tools.

I'm not sure what you mean.
Did you mean that because of the open source nature of Ocpn, the data produced with it must be "open source" too? This is not the case. I can use an open source word processor to write a completely closed source text or even a proprietary program.
Naturally- all the data that gets entered into the OSM database must be under their cc-by-sa license.

It is possible to use OpenStreetMap XML format as internal one and then either post it directly to OpenStreetMap or convert to some other format for some other system depending on user's choise. The idea here is that even if we decide to go with different services support we still can elaborate the format and tools for our use instead of designing from scratch.

Writing an editor for OSM doesn't seem to be trivial. To my knowledge there are at least 3 allready in existence (JOSM, Merkaartor, Potlach)- IMHO all of them are free software.
An online Editor for nautical seasigns is currently under development by the OSeaM project. They are looking for developers that can write Java and PHP.
IMHO writing an editor for OpenCPN is a wasteful dupliction of efforts. Also, noone can guarrantee that the data consitency that is produced by all the different editors (different upgrade cycles etc.).

[antonm]

Originally Posted by zenfunk

They currently develop a OSM xml tagging scheme that is somewhat as feature rich as S57. Converting that to S57 shouldn't be a problem then.

Originally Posted by zenfunk

Anybody here that is willing to write a osm2s57 proggie?

I also think that this is the best option, especially since tagging is OSM is already S57 based. I decided to give this a try and check out if I can write such a converter myself. No warranty about time frame. I did not studied S57 reference yet.

Originally Posted by zenfunk

What I really would like for OSeaM is a worldwide datadump. If you ommit the data further inland, I think the filesize should be comparable to the c- maps- something like 2 cd- roms.

Yes, it is possible to filter the OSM data out when creating such offline packages, so the only needed information is there and you'll get a fair amount of data that is possible to take with you on boat.

Originally Posted by zenfunk

This is not the case. I can use an open source word processor to write a completely closed source text or even a proprietary program.
Naturally- all the data that gets entered into the OSM database must be under their cc-by-sa license.

That is exactly what I mean. If you post the data to OSM database, this means that you license it as cc-by-sa and later OSM will propose to relicense under specially developed ODBL. This just needs to be taken in mind, cause only third party systems that conform to "sa" clause will be able to incorporate such data. I personally think that it is good, but other people way have other views, so I had to warn about such drawback.

Originally Posted by zenfunk

Writing an editor for OSM doesn't seem to be trivial. To my knowledge there are at least 3 allready in existence (JOSM, Merkaartor, Potlach)- IMHO all of them are free software.

However it may be easier if you can tag things on the fly in OpenCPN itself. But, anyway this is completly separate subjects: "display data from OSM" and "push data to OSM".

[zenfunk]

Originally Posted by antonm

That is exactly what I mean. If you post the data to OSM database, this means that you license it as cc-by-sa and later OSM will propose to relicense under specially developed ODBL. This just needs to be taken in mind, cause only third party systems that conform to "sa" clause will be able to incorporate such data. I personally think that it is good, but other people way have other views, so I had to warn about such drawback.

Hm, never gave that issue much thought, but probably I'm more into this free software thing than the average sailor. For me, copyleft licenses are a positive thing and usually guarantee a certain level of quality.

However it may be easier if you can tag things on the fly in OpenCPN itself. But, anyway this is completly separate subjects: "display data from OSM" and "push data to OSM".

You are right, it would be easier to map stuff within OpenCPN, on the other hand I really would like to see OpenCPN to stick to the Unix mantra that a program should do one thing and one thing only. If you add mapping capabilities, then you can also add something to update your APRS log, edit geotagged wikipedia articles, various sailorguides etc. Then it will become something like the nero burning suite- the swiss army knife of multimedia that needs a dual core to start in an aceptable time.
Let OpenCPN be the best chartplotter that is for now. Probably additional functionality can be added as plugins further down the road, but now, I feel that the development should focus on he core - chart plotting.

BTW, a osm2s57 converter would be marvelous, I think the openseamap guys would have a great interest in that and could give support.

[idpnd]

Originally Posted by antonm

That is exactly what I mean. If you post the data to OSM database, this means that you license it as cc-by-sa and later OSM will propose to relicense under specially developed ODBL. This just needs to be taken in mind, cause only third party systems that conform to "sa" clause will be able to incorporate such data. I personally think that it is good, but other people way have other views, so I had to warn about such drawback

There was a big discussion about this on another thread and I did feel most people regard this sort of license as an advantage, since it protects submitted data and ensures continuing public availability.

[antonm]

Originally Posted by zenfunk

You are right, it would be easier to map stuff within OpenCPN, on the other hand I really would like to see OpenCPN to stick to the Unix mantra that a program should do one thing and one thing only.

I totally support this and it means that no changes to OpenCPN needed if one will be able to download OpenSeaMap in S57 form.

Originally Posted by zenfunk

BTW, a osm2s57 converter would be marvelous, I think the openseamap guys would have a great interest in that and could give support.

I contacted OpenSeaMap with help offer and clarifications of if they already have something in this field and their intentions about it.

[sinbad7]

antonm...

GREAT!! This is exactly what the OpenSeaMap developers are looking for. As a non profit outfit they have a very limited budget and welcome any help to make their mapping system more accessable. As I understand it,OSM is already S57 compatible but is slightly altered using longer sentences. Perhaps it should not take too much work to make it compatible? Keep up the good work!!!