Another GPS/sat nav question

[Diff]

I have never used a sat nav or a GPS system before and I have a couple of queries.

I am taking the family on a 3 week overland safari next year, and some of the places we are going are pretty remote. I have the GPS coordinates for some of the main 4x4 track junctions. There can be many tracks and it would be very useful to know when we are at the right track junction.

1. What would be a simple and cheap method of finding my position in Botswana?

2. I was thinking of buying a simple second hand in car sat nav for around £30 here in the uk. I know it would have uk mapping, but would it display my GPS location when in Botswana?

2. Can you get electronic maps for places like Botswana?

3. Can they be downloaded onto a cheap s/h sat nav?

I am not hugely bothered about electronic maps of Botswana, though they would be useful if they are free/easily available, just a receiver to tell me where we are would be useful.

I have always managed fine without in the past, but it might be useful, so any tips, advice or whatever would be greatly appreciated.

Regards,

Diff

[Guest WALFY]

I have the Garmin XL12. You can put in waypoints and it will nav to them as the crow flies. If you want it for peace of mind then that will be enough. Not sure on maps of that area of the world.

I'm sure a grown up will be along shortly to point you in the right direction.

As for suitability of my GPS, it will give you your location in UK, Canada, Iraq and Afghan to name a few so should be good for every where else. You just have to set the system to suit the country your in. In the UK I think mine is set on WGS ?? Again you need a grown up for that info as to what to use. They are all in the setup menu.

HTH

[western]

I have a 12XL too, mines set for UK OS Grid ref's on WGS84, it'll do most of the known map reference system that are/have been used to make maps & it'll do latitude/longitude too, which might be better where your going.

[discojmz]

I have a 12XL too, mines set for UK OS Grid ref's on WGS84, it'll do most of the known map reference system that are/have been used to make maps & it'll do latitude/longitude too, which might be better where your going.

you're using two different datums there then Ralph WGS84 is the standard for admiralty nautical charts but ordnance survey maps are datum OSGB which has a different correction to magnetic north; around 3 degrees west here and decreasing, whereas WGS84 is about 6-7degrees and decreasing

[western]

you're using two different datums there then Ralph WGS84 is the standard for admiralty nautical charts but ordnance survey maps are datum OSGB which has a different correction to magnetic north; around 3 degrees west here and decreasing, whereas WGS84 is about 6-7degrees and decreasing

I'll check that then, it definitly displays spot on OS grid ref's to 12 figues including the 2 letter prefix.

I know where the WGS84 bit has come from on my memory map on the laptop it's got os grid ref then WGS84 in brackets in the status bar bottom of screen, knew I'd seen WGS84 somewhere.

[discojmz]

from memory map's help

The position indicated by the software is on the WGS84 datum, whereas the map's lat/long grid may have been printed on a different datum. The software automatically determines the datum shift necessary for each map, and converts positions to the WGS84 datum.

i guess this is because memory maps does OS maps, marine charts, and mapping by other companies so it converts them all to some common ground. also technically WGS84 displays true north, which of course OSGB does not, which is no doubt why mem map uses it. it's the most commonly used gps datum. if the ordnance survey would produce WGS84 mapping in the first place, we'd all be laughing!

if anyone like me has old skool paper maps then this can be found on the legend (mine from laminated explorer OL2 - yorkshire dales southern and western)

base map constructed on transverse mercator projection, Airy Spheroid OSGB (1936) datum. Vertical datum, mean sea level (Newlyn) correction on the south sheet is 3 degrees 11minutes west, on the western sheet 3 degrees 4 minutes west, correct as of july 2007

if you're using your handheld alongside mapping on mem maps then having them both ws84 is no issue, if you're using your handheld with paper maps it will still be a smallish error, but an error nonetheless. it can make quite a difference.

ive just checked and memory map doesnt list an OSGB datum but does give you the option to load in such a datum should you be able to get the grid file for it... which im going to attempt to find just so ive got everything working on the same datum

hopefully thats some help

jim

[jpk]

Once you have a receiver sorted out, you could try having a look at www.tracks4africa.com. We used it earlier this year on a 4 month trip round Southern Africa and found it very useful. You have the choice of buying only the country you need and i thought it was very reasonable pricewise.

JP

[Diff]

Thanks Walfy and Ralph, I think I will go with JPs suggestion as it seems to offer everything I need and more, for not much more money if I buy second hand:

Once you have a receiver sorted out, you could try having a look at www.tracks4africa.com. We used it earlier this year on a 4 month trip round Southern Africa and found it very useful. You have the choice of buying only the country you need and i thought it was very reasonable pricewise.

JP

Thanks very much JP I have had a look at the site and it looks just the thing to make life easy. According to the site I need a Garmin to load the maps on to, so I will be on the lookout for a cheap s/h garmin sat nav I guess.

Regards,

Diff

[jpk]

No worries.

Just make sure you get the mapsource (Garmins map management program) stuff as well for your pc. T4A works on this. I'm not sure if T4A would work on something like the new Nuvi etc We had a 60cx which was great. Just check whatever you get will be compatible. I don't actually know enough about this stuff, but I did have an older Garmin V which could use T4A. That was pretty cheap on the bay.

JP

[Brian]

No worries.

Just make sure you get the mapsource (Garmins map management program) stuff as well for your pc. T4A works on this. I'm not sure if T4A would work on something like the new Nuvi etc We had a 60cx which was great. Just check whatever you get will be compatible. I don't actually know enough about this stuff, but I did have an older Garmin V which could use T4A. That was pretty cheap on the bay.

JP

T4A works on any map capable Garmin, so yes, it works on the entire Nuvi range.