If you could have your dream GPS cycling map...

[drossall]

It shows the limit of the visualisation. That bump two lines down and left of the 250 label should be a depression into the hillside to keep the contour level.

[andygates]

I've worked out how to do custom icons on the Garmin.  The wrestling match with OSM Composer ran foul of the language barrier: I could blag my way around the program, but the German tooltips that appeared on the non-routable map, no, that didn't float my boat.  Give it a while to get out of beta.  Still, it showed srtm2osm, which is a neat tool for grabbing high-res contours from the NASA database to build into OSM-format (and hence into Garmin transparent overlay if you felt the urge).

This icon business is, of course, for bike shops, which OpenStreetMap defaults to either nothing, or the boring shopping-basket icon. Custom icons are full of fail, because with 32x32 and a full alpha channel to play with, I can see myself wasting huge swathes of time getting my maps just so.

How-to:  It's a two-stage thing.  First, define a mkgmap style for the tags you want to use.  That means that the map objects get marked with the correct Garmin TypeID.  Shops are 2e, with the higher numbers unused, so 2e10 is bike shops (tag: shop=bicycle) to me.

Second, build a custom Typ-file (a Garmin binary that holds the colours and graphics) using the online editor.  The neat thing here is that if you define very little, the rest will appear as defaults, so it's quite hard to break it.  It's very easy to make something hideously gaudy, mind!  The typ-file styles all elements - land, ways and points - so at some point I'll start painting buildings and I'll colour the roads to match UK road signs, which is intuitively right to me.



 

[TimO]

TimO uses a device which has OS Landranger quality maps. I think it must have lots more memory.

It's a Satmap Active 10, with the bottom half of the UK in 1:50000 OS mapping (ie Landranger).

I think my mapping is on a 4G card, but it has used up less than half the card.  I believe that the entire country mapping also comes on one card (for just under £200).

They don't sell large swathes of the country in 1:25000, as they do for the 1:50000.  The best you can do is the site centred custom mapping, for which you can buy a 110km x 110km chunk for around the same as the entire country at 1:50000.  If the entire country was available at this price, it would be close to £4000 !

[TimO]

I wondered exactly how big the OS mapping is, so I dug out a reader and popped them into the PC to check.

The 1:50000 Southern England (from about the top of Wales downwards) is 1.4GBytes of a 2GByte card.

Surprisingly, the 1:14000 A-Z of London is only 82MBytes of a 256MByte card.  Given the relatively high level of detail, I expected it to be bigger, but I guess the area covered (roughly everything inside a square that includes all the M25) is still quite small.

Assuming that the Northern half of England is much the same size as the Southern half (and I think the maps have a fair amount of overlap), then the whole lot would fit on a 4GByte SDHC card.  Originally the Active 10 couldn't use SDHC cards, only SD, but I think one of the more recent firmware updates enabled this.

[andygates]

London's pretty flat, and I'll bet that a lot of that data turns out to be the contour lines, so the lumpy bits end up as data-rich as the flat bits.

[TimO]

The Satmap mapping seems to be raster, only the base mapping (on the device itself) is vector.  The 1:14000 has quite a lot of information, the maps are quite busy, so I wouldn't have thought it ideal for compression.

Having a look at the device, I reckon the coverage is about a square of about 40 miles on a side, and the pixels look to be around 1m across, so that would need about 4 GPixels.  80MBytes is about 1 Byte per 50 Pixels, which doesn't seem like too extreme a compression ratio after all.

(The 1:14000 A-Z map isn't from the OS, it's from A-Z Mapping, and doesn't have any contours).