online map: OpenNauticalChart.org
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- no raster tiles (needed to generate .kap charts ...)
These can be generated by command-line calls to Inkscape. This is how I generated the seamark PNG tiles until very recently.
I do not like those "let me google for you" buttons.
+1
Google is a commercial bloodsucker.
- adding and maintaining links to OSM-db will be a pain
- this also applies to seperate 'harbour-db'
A link only has to added once, whereas the data linked to will be constantly changing. Also it will not be us who add these links - it is the DB operators who would be encouraged to do that work.
- click on harbour icon 'Alter Hafen Wismar'
- pop-up key=value box
- offer 'search skipperguide' button/link
Remember 90% of viewers are not mappers - they will not understand keys and their values. Any pop-up box must translate key/value pairs to plain language.
The scheme has to be global, whereas the various harbour DBs only have local extent. Therefore offering specific DB buttons would not be a workable scheme.
If we were to have tags of the form: website:<DB name>=<DB URL>, then harbours/marinas/anchorages with these tags would present the link(s) in the pop-up.
The best way to do that is to add links to the various marina guides to the harbour object. That way, clicking on the link (which also would have to be displayed in the pop-up panel) will take the user to the up-to-date entries in those guides. We can then encourage to operators of those sites to add the link tags in the areas that their guides cover.
We don't have to - Olaf has a much better scheme & it is visible right now. Find a harbour or marina and click on it - details will appear.
The OSeaM scheme was to try and import & merge data from disparate sources, most of which provide inadequate details or poorly located positions. The problem then remains how to maintain this data? When the original sources are updated, our import would become stale, so requiring constant re-importing and editing. Nobody has time for this!
- clickable objects (I started this feature already. It is only working for harbours at the moment, but can be easily enhanced for all objects. It uses overpass.api.
Olaf,
Do I take it that you do not need the "harbours.xml" data? If not, I will no longer generate it. I originally did this after a request from somebody as OSeaM, but it was never used.
OK, I will not do any more work in this area until the final scheme is decided.
I have made a small utility that may of interest for the online map. It provides the data needed for display of a compass rose with magnetic variation & direction of buoyage pointers. This is what the output looks like:
imac:jseas mherring$ java -jar jseas.jar s23.osm
Enter lat,lon:
53.73,-.33
Upper Humber, North Sea
Buoyage: 260
Magnetic Var: -1.090067
It takes its data from a world map of oceans (the file s23.osm) and also calls a modified version of the NASA WMM program.
To minimise server load, the rendering could be done on demand, maintaining a cache of previously viewed tiles. I will do some tests to check the feasibility.
On a map at zoom 12, the area displayed is approximately that of a zoom 9 tile, so I did some test extractions of z9 areas. Even on my local SSD-based Overpass, it took 30 seconds to execute. Clearly this is too long to wait, so pre-rendered tiles would be necessary. As most of the world is either 100% land or 100% sea, most z9 tiles would map to one of two solid colour tiles. The renderer would only make tiles in those z9 areas that contain coastlines or riverbanks. I estimate that such a tile library would occupy about 100GB.
- my favorite inland base map: https://github.com/yohanboniface/OpenRiverboatMap
This looks like a suitable replacement for the default OSM base map. Is there an existing tile server that we could use or would we have to make our own?
Summary of discussion so far:
Olaf:
The next steps I want to do are:
- Render a nautical base map (user should be able to switch between different
maps)
Malcolm:
My new renderer can already do this - see: http://sourceforge.net/projects/opensea … p/download
Olaf:
Looks great.. What do you need to get it up and running? Do you know how big
the resulting tiles directory will be? May be we need an additionbal server
for it.
Malcolm:
Given that the map detail consists only of line elements, with no text or icons, then the map could be stored as a set of SVG tiles that would be scaled according to the zoom level being viewed. The storage required would therefore be very modest (SVG also compresses well).
To minimise server load, the rendering could be done on demand, maintaining a cache of previously viewed tiles. I will do some tests to check the feasibility.
I have safely landed!