Be aware, that GPS Devices may have a limit for the size of maps. And be aware, that computing times (Zoom changes, adress search…) are larger for big maps.
So I have some concern, if a worldwide map of some detail will solve your problem.
If you have modern GPS devices which have Micro SD Cards, there the following procedure is feasable:
Divide the world in several parts of moderate size (Lower 3GB ?) and produce maps XXX.img for all this parts. The xxx must be different for all maps. (And if you want more than one map to be active at the same time, they must have different FID). Now look to your GPS devices and check which max micro SD card they can handle (I work on my Oregon 450 with a 16 GB SD card, larger cards i did not check). The map who is active must be stored in the Garmin folder of the SD card. The other maps should be stored in the root of the SD card. If the maps all are on the same SD card, some on the root, one ore some in the Garmin folder, the transfer between root and garmin folder runs very quick with Ctrl+X and Ctrl+V on a windows computer.
Another possibility is to use different micro SD cards and to change them during your flight to the destination. The whole Asia or the whole of Africa is smaller than 3 GB. For the whole of Europe I guess you may need 4-6 cards of 3 GB size.
Maximum img size is 4 Gb, but this wont fit on a 4 Gb micro SD card, so I guess an optimal maximum would be 3,5 Gb.
The maximum number of tile segments on most modern Garmin devices is around 4,000 so that wouldnt be a problem.
My OFM Europe (full version with contour lines) is ~8 GB which fits on a 16 Gb card.
I am sure Ligfietser would know how the system works and then there’s support for the OSM Foundation.
http://wiki.osmfoundation.org/wiki/Main_Page
Not sure what exactly Sojo needs for his mapping. But coverage for Asia/Africa can be quite limited except at a very basic level or potentially non-existent in areas. Use with caveat I guess. Still, OSM is quite a project and I enjoy contributing to it when possible.
We are using current hardware (Garmin GPSmap 62s for now and currently testing if the specs of the new 64s would justify swapping the devices). So I hope we can cope with larger maps.
That’s logistically impossible. Having 40+ devices with each ~ 5 SD cards and having to update all of them every time when an updated map is applicable. We don’t have the resources for this. The same for purchased ready-to-go maps of Garmin etc. Having these maps (if they’re even available) for that many devices of every country/region just for the case that something might happen somewhere would cost 10s of thousands of Euros just for the procurement. Not to mention the management of the cards. I think this kind of money is better invested in aid projects or OSM.
My dream would be having a world map for general orientation (one file) in an acceptable zoom level (best effort) that fits on a 16GB microSD card and is updated ~ 4 times per year. If it is several files which can be downloaded/copied at once that would be fine as well. But I don’t know how detailed a world map on a 16GB SD card that runs smoothly with our devices can be? Maybe it’s not even worth a try and it wouldn’t be notably better than the Garmin Basemap at all? Can anyone answer this?
This would allow us to use the devices in any area of the world for our response teams during the emergency phase until we generated/purchased/downloaded/created detailed maps of the affected area which usually takes about 1-2 days + 12-24 hours for shipping if there is no suitable internet connection. Of course I’d prefer to have all zoom levels of every spot on earth at hand. But our SD cards are only 256 TB and I think we’d need a bit more than 300 TB for the whole database. Bummer! 
You can easily grab the whole world with the manual tile selection on http://garmin.openstreetmap.nl/
Europe, which is the most detailled continent by far, needs 6Gb which runs fine on a modern GPS like the 62.
The Americas 4Gb, Asia+Oceania 2Gb, Africa 0,5gb, so the whole world would fit perfectly on a 16 GB Sd card.
But isn’t the number of tiles you can select limited?
What features do you need on maps?
For example do you need routing, address search, POI search, local names in Unicode, topo objects, contour lines?
Some features are not yet supported by mkgmap compiler, for example search in Unicode. Most features takes space on SD and increase number of tiles. I think that map of the world with contours and all features available now would be about 30GB and probably over 4000 tiles. You would need 2 SD cards tor it.
I’m trying to compile small maps for wide area. I remove routing and reduce a bit precision. My map of Asia (no contours) is about 1.2 GB. Map of Africa with 100m contours is about 600MB. See:
http://www.gmaptool.eu/en/content/asia-osm-base
http://www.gmaptool.eu/en/content/africa-osm-topo
The tile limitations are limited because of two reasons:
The first limit is 2GB for the Windows installer.
Between 2GB-4Gb there is no windows installer, but you will still get the gps version.
So it needs roughly 4x a custom map generation to grab the whole world, for free.
Of course you can show your appreciation afterwards with the donate button on the website 
Sojo,
I know that during the Haiti crisis Geofabrik created a new map for the island every 5 minutes and that these maps were used by aid workers on the ground who got regularly new updates while being there. This is ofcourse something different then having a pre-installed map, ready to go, which is what -it seems- you are looking for.
The is not a global map provided because, as was said earlier, it got abused and people wasted valuable bandwidth and other resources. But if you’re looking for a basic map that is only updated e.g. 4x a year (just for basic coverage) then I think we could make provisions for that.
Let’s try and see what’s possible and needed.
Do you need routable maps?
Do you need altitude profiles?
Do you need landuses or only (rail-)ways?
Do you need oceans shown in the maps?
I’m curious what organisation you work for. If you don’t want to share this, then you can also contact me privately: osm at na1400 dot info
Yes we did (and still do) work with this map in Haiti.
And we’re just about to go to Serbia and Bosnia. Again with OSM maps.
Exactly. A general map to replace the useless Garmin World Map when handing out GPS devices - as detailed as it gets considerung the space limitations.
Do you need routable maps? → 7
Do you need altitude profiles? → 3
Do you need landuses? → 6
Do you need (rail-) ways? → 10
Do you need oceans shown in the maps? → 5 | coast lines for orientation purposes only
1 = not necessary / 10 = indespensable
Swiss Humanitarian Aid
I don’t have any experience in these matters. Can you tell me how much time it takes you to build such a map and if there is a way to get it automatically done with your service or I’d have to get you involved every time there needs to be an update? I’m happy to talk about this in private (simon dot joss at eda dot admin dot ch). If you’re telling me that there is a way to do this with little administrational effort I’d like to discuss that in our organization and get the approval so I’ll be able to do a donation as well.
Win
Win
Sojo, why don’t you try it yourself by using the manual tile selection. To grab the whole world you need to divide it in 6 parts.
N+S America, Africa, Europe (N and South?) Asia+Oceania. Then download the gmapsupp.img versions and rename them. They all fit on a 16 GB card that can be read on your Garmin 62 device.
See for an excellent tutorial http://www.dcrainmaker.com/2013/05/download-garmin-705800810.html
I’m happy to do so. Just wanted to know if there was an easier way.
Thanks for your support!
A question on the colour contrast b/n the green of national parks and blue of rivers/creeks.
Downloading using the ‘new styles’, I am finding it’s very difficult to differentiate the river/creeks when they are over a green background of national parks e.g. Nattai River in Nattai NP (34S34° 17’ 19.9" E150° 20’ 48.1"). Is there a way to overcome it? Thanks.
You can try to edit the typ file with typviewer and copy paste the following code
on line type 0x18 (streams)
[_line]
Type=0x18
UseOrientation=Y
LineWidth=1
BorderWidth=1
Xpm="0 0 4 0"
"1 c #7BCAD5"
"2 c #DDF1F4"
"3 c #00008B"
"4 c #DDF1F4"
String1=0x04,stream
String2=0x03,beek,sloot
String3=0x02,Bach
ExtendedLabels=Y
FontStyle=SmallFont
CustomColor=Day
DaycustomColor:#0000B4
[end]
This gives a lighter border to the line type, but the results are not good when a waterway inside a water polygon is drawn:
See the preview section at https://www.dropbox.com/s/17uw0dp69g0qve9/water.jpg
Wow. Thanks! I’ll see if I can get a Windows machine to try this.
routing around Boston Massachusetts gave me a remarkable result.
A bunch of ppl have been busy trying to get a bicycle route up and have partially succeeded, northern strand community trail.
http://www.biketothesea.com/
On osm.org the trail has been drawn and access is allowed for foot and bicycle.
However basecamp with a just freshly generated map refuses to route over the trail, not with any of the walking or bicycle options.
spot where I tried to route
http://www.openstreetmap.org/#map=19/42.43040/-71.04287
Those bunch of ppl should have done their homework better. This bike trail is dead ending at a railway.
No wonder Basecamp refuses to ride there
https://www.openstreetmap.org/way/227602980#map=18/42.43237/-71.02531
Maybe a situation like this?
it is an old train track and i did say partially succeeded
Still I think there is no setting on osm.org that would make basecamp not route over that trail, yet it does not… scratch that I think I just found the issue, there are no nodes on the intersection:rolleyes: