#1 2015-12-12 09:04:29

malcolmh
OpenNauticalChart Developer
From: Hull, GB
Registered: 2015-12-07
Posts: 32

INT-1 Base Map

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.

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#2 2015-12-12 10:31:09

Dirk--
Administrator
From: Ruhrgebiet
Registered: 2015-12-06
Posts: 42
Website

Re: INT-1 Base Map

- my favorite inland base map: https://github.com/yohanboniface/OpenRiverboatMap

- http://tilestache.org/ is the tile server I prefer:
-- raster tiles
-- vector tiles
-- cache
-- proxy
...

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#3 2015-12-12 12:50:05

malcolmh
OpenNauticalChart Developer
From: Hull, GB
Registered: 2015-12-07
Posts: 32

Re: INT-1 Base Map

Dirk-- wrote:

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?

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#4 2015-12-12 13:04:10

malcolmh
OpenNauticalChart Developer
From: Hull, GB
Registered: 2015-12-07
Posts: 32

Re: INT-1 Base Map

malcolmh wrote:

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.

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#5 2015-12-12 15:42:00

Dirk--
Administrator
From: Ruhrgebiet
Registered: 2015-12-06
Posts: 42
Website

Re: INT-1 Base Map

malcolmh wrote:

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?

They do have a tile server (rather slow). Yohan is a friendly guy and had no problem passing requests: I am using a proxy (tilestache) in case of my maps (maps.grade.de) and skipperguide's maps.

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#6 2015-12-16 14:21:10

Dirk--
Administrator
From: Ruhrgebiet
Registered: 2015-12-06
Posts: 42
Website

Re: INT-1 Base Map

an other approach: Use of vector-tiles.

Did some tests with
- mapzen's water and landuse layers https://github.com/mapzen/vector-datasource
- mapbox-gl-js (some of the magic is included in ol3) https://www.mapbox.com/mapbox-gl-js/api/
It is fast!

Drawbacks:
- no raster tiles (needed to generate .kap charts ...)
- styling can be a pain

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#7 2015-12-16 16:33:50

malcolmh
OpenNauticalChart Developer
From: Hull, GB
Registered: 2015-12-07
Posts: 32

Re: INT-1 Base Map

Dirk-- wrote:

- 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.

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#8 2015-12-16 17:37:51

Dirk--
Administrator
From: Ruhrgebiet
Registered: 2015-12-06
Posts: 42
Website

Re: INT-1 Base Map

@Malcolm, vector tiles: Not vector graphics, post was on
raw data (feature=node|line-string|polygon + geometry + key=value list) and on device rendering ...

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#9 2016-01-02 11:04:31

malcolmh
OpenNauticalChart Developer
From: Hull, GB
Registered: 2015-12-07
Posts: 32

Re: INT-1 Base Map

I have started rendering the SVGZ tiles & uploading to the OSeaM tile server. You can find them at: http://tiles.openseamap.org/int1base/<x>/<y>.svgz where x & y are zoom-9 tile numbers. As each tile covers a zoom-9 area, to display at other zooms they will need to be scaled by a factor of 2^(z-9).

Both Olaf & Axel have said that they will work on a base layer using these tiles.

Happy New Year to all!

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#10 2016-01-25 12:24:15

Dirk--
Administrator
From: Ruhrgebiet
Registered: 2015-12-06
Posts: 42
Website

Re: INT-1 Base Map

visit
  http://maps.grade.de/int1.htm
to evaluate Malcolm's tiles

please note:
- tiles load slowly
- thus display is intentionally reduced to 512x512 pixel
- chrome works best, firefox might quit

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#11 2016-01-25 13:42:24

malcolmh
OpenNauticalChart Developer
From: Hull, GB
Registered: 2015-12-07
Posts: 32

Re: INT-1 Base Map

No problems with Firefox here.

Is the slow loading a limitation of your upstream bandwidth?

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#12 2016-01-25 13:57:57

Dirk--
Administrator
From: Ruhrgebiet
Registered: 2015-12-06
Posts: 42
Website

Re: INT-1 Base Map

malcolmh wrote:

Is the slow loading a limitation of your upstream bandwidth?

- http://tiles.openseamap.org/ serves the tiles
- .svgz tilesize is ~7 MB
- .png tilesize is ~ 40 KB

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#13 2016-01-25 16:21:49

malcolmh
OpenNauticalChart Developer
From: Hull, GB
Registered: 2015-12-07
Posts: 32

Re: INT-1 Base Map

OK, given this experience, I could instead generate a set of tiles of zoom-12 size. This would reduce the tile size to ~100kB, but not take up much more space on the server. For lower zooms, I could make a set of sea-, river-, lakes- and land-only tiles at zoom-9 size (these would be much smaller as most of the content of the full-feature tiles is roads, railways, man-mades & landuse). I could also do a set of land- & sea-only tiles at zoom-6 size.

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#14 2016-02-04 10:23:44

Dirk--
Administrator
From: Ruhrgebiet
Registered: 2015-12-06
Posts: 42
Website

Re: INT-1 Base Map

updated: http://maps.grade.de/int1.htm

Malcolm serves 3 zoom-levels now:
- Z6
- Z9
- Z12

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#15 2016-02-09 11:40:10

malcolmh
OpenNauticalChart Developer
From: Hull, GB
Registered: 2015-12-07
Posts: 32

Re: INT-1 Base Map

I have rendered Z6-8 globally, Z9-11 Europe & have started Z12-18 Eire/Britain. All three directories are fully populated, mostly with blank tiles. I have deleted the original set of tiles (directories 0-511).

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#16 2016-03-25 13:38:32

Menno
Member
Registered: 2016-02-03
Posts: 2

Re: INT-1 Base Map

I like the idea of having a base map without all the land details of the default OSM Mapnik layer, but I think the blue color for the sea is too dark (on paper charts with INT-1 symbols most water is white).

The contrast with other features (e.g. TSS) is too low:
scxklj.png

In this picture I changed the blue color to a lighter shade (#bedef5) and added a coastline (0.1px black line):
rwpil3.png

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#17 2016-03-25 16:12:34

malcolmh
OpenNauticalChart Developer
From: Hull, GB
Registered: 2015-12-07
Posts: 32

Re: INT-1 Base Map

The shade of blue I chose is close to the shallow water blue. My intention is to use the GEBCO depth data to generate lighter blues for deeper water. I am thinking of using a light blue (like the shade that you have demonstrated) in the 20-50m range & >50m use white.

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