Maps

March 24, 2002

I don't usually need to use a map when I am out caching. Occasionally though, if trying to plan the best route for hunting several caches, I find a map can save me time, money and petrol.

The map I currently use is an OS Routeplanner foldup jobbie that I bout 12 years ago, that covers the whole country, with a scale of 1 inch to 10 miles. This is a bit crap for any sort of accuracy. However, I have been unable to find a larger scale map that has Lat/Lon markings on it.

I know things like Chris' spreadsheet will convert to OSGB, and that would open a floodgate of available maps. But at the moment Lat/Lon is my preferred choice.

Can anyone recommend a particular map to me (and perhaps where I can buy it from?)

--Mark

P.S. Sorry if this topic has been covered before in the forums. I checked back as far as I could and couldn't find a thread that covered it.

Mark

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I was technical once

March 24, 2002

OS 1:50000 Landranger maps do have lat/long on them as well as grid refs. Unfortunately they probably use the OSGB36 datum which means that your way points will be about 100 metres out (you can argue that that is the accuracy of a six figure grid ref anyway I suppose

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jeremyp

We're going to need a bigger boat!

March 25, 2002

If you have a laptop, you can get an OS cd that you can zoom to 1:10,000.

I've got the cd but no laptop, so if planning i just print out a map of the area.

I must amit this takes a bit of forward planning and i usually just take the gps

1.4k · March 25, 2002

I'd try to let the GPS do the work for me. Enter the wapoints as lat/long then change to OS grid on the GPS and you can find your location on the map. Seems to work on my etrex - though not sure if all GPS's can do it.

Chris

"We're not lost - we just don't know where we are"

London & UK Geocaching Resources

March 25, 2002

I'm a girl so, naturally, unable to read one

March 25, 2002

I'm a girl so, naturally, unable to read one

March 25, 2002

Ahh yes, girls and maps. Rather like giving Bob Geldof a hairbrush: complete waste of time

Thank you all for your suggestions - all good and valid ones. Really though, I'm looking for something with the convenience of my current AA road atlas, but with lat & lon markings. Something I can just pick up and see if I am in the right area, without having a stack of Landranger maps in the boot; without having to switch on the Garmin and without having to fire up the laptop (I have some software and it's very good ).

I am coming to the rapid conclusion that my ideal mapbook doesn't exist outside of military circles.

Mark

----------------------

I was technical once

March 25, 2002

Ahh yes, girls and maps. Rather like giving Bob Geldof a hairbrush: complete waste of time

Thank you all for your suggestions - all good and valid ones. Really though, I'm looking for something with the convenience of my current AA road atlas, but with lat & lon markings. Something I can just pick up and see if I am in the right area, without having a stack of Landranger maps in the boot; without having to switch on the Garmin and without having to fire up the laptop (I have some software and it's very good ).

I am coming to the rapid conclusion that my ideal mapbook doesn't exist outside of military circles.

Mark

----------------------

I was technical once

March 25, 2002

I've just sent an e-mail to Stanfords. If they don't know of something that fits the bill, I suspect it doesn't exist. Fingers crossed!

March 25, 2002

quote:
Originally posted by BumbleBee:
I'm a girl so, naturally, unable to read one

LMAO - and don't I know it

March 25, 2002

quote:
Originally posted by BumbleBee:
I'm a girl so, naturally, unable to read one

LMAO - and don't I know it

March 25, 2002

Elstead Maps ? They seem to have a map for almost everything - their site is a bit of a nightmare to navigate, but they are a specialist map seller, and I can't fault their Customer Service.

[This message was edited by JasonW on March 25, 2002 at 01:22 PM.]

March 27, 2002

quote:
Originally posted by JasonW:
Elstead Maps ? They seem to have a map for almost everything - http://www.elstead.co.uk/ is a bit of a nightmare to navigate, but they are a specialist map seller, and I can't fault their Customer Service.

Is this an 'in joke' or something? It seems OK to me. Tabs at the top of each page, and highlighted links to various products.

--... ...--

Morseman

March 27, 2002

quote:
highlighted links to various products

The broken product links to the OS website don't help though. Whatever...

Purrs... LazyLeopard http://www.lazyleopard.org.uk

1.4k · March 27, 2002

I've been spending quite a lot of time looking at the OS site lately and read some very dull publications with huge formulas in them. The conclusion I have come to is that you won't find a map based on WGS84 of the UK....I could be wrong but here is what I think I have worked out.

A map is only an abstraction of the world, any map involves the conversion of 3d lumpy curved surface to a flat 2d surface. Now as the world isn't a completly flat sphere, map makers have to choose a curve to base their calculations from (technically known as an elipsoide). OS use an elipsode that matches the curve of the earth round the UK where as WGS84 uses slices that are more generalised for the whole of the earth.

Heights add another level of complexity as they are relative to a complex mathematical shape known as the Geoid for WGS84 but OS was originally based against Mean Sea level in Newlyn at cornwall. Aparentley sea level round the UK is below sea level - Go figure!

Conversion between the 2 systems is a non-trivial operation which in the case of OS to WGS84 involves Guessing the co-ords and iterating till it gets to the right answer.

So the upshot of all this is that a map made to WGS84 will look subtily different to one made to OS refs. I kind of think it unlikely that someone would remap the entire country, just for us GPS users.

Of course I could be wrong. If any surveyours are reading this - please be gentle.

Chris

"We're not lost - we just don't know where we are"

London & UK Geocaching Resources

March 27, 2002

quote:
Originally posted by Morseman:

Is this an 'in joke' or something? It seems OK to me. Tabs at the top of each page, and highlighted links to various products.

--... ...--

Morseman

Certainly not - try looking for a particular OS Pathfinder, Explorer or Landranger map - last time I looked for one it was a nightmare.

March 27, 2002

quote:
Originally posted by Chris n Maria:
I've been spending quite a lot of time looking at the OS site lately and read some very dull publications with huge formulas in them. The conclusion I have come to is that you won't find a map based on WGS84 of the UK....I could be wrong but here is what I think I have worked out.

Actually, I found all that stuff quite interesting Last time I went sailing I noticed that all the navigational charts we had were WGS84 except for the ones around Cornwall. I guess they were going through a process of converting from OSGB to WGS84 at the time.

As almost all mapping data of the UK comes from the OS and they aren't changing just yet, your comment is probably right, but for most purposes irrelevant, you just make sure your GPSr uses the right datum.

quote:
Heights add another level of complexity as they are relative to a complex mathematical shape known as the Geoid for WGS84 but OS was originally based against Mean Sea level in Newlyn at cornwall. Aparentley sea level round the UK is below sea level - Go figure!

The mean sea level at Newlyn only defines the zero for heights on OS maps. Heights in the UK still use the geoid which is defined as a surface with a constant gravitational field. If you map out a level surface it *will* be parallel to the geoid which varies depending on the density of the Earth's crust. A datum such as WGS84 is essentially arbitrary (we can put the prime meridian anywhere). The geoid depends on the physical characteristics of the Earth.

quote:
Conversion between the 2 systems is a non-trivial operation which in the case of OS to WGS84 involves Guessing the co-ords and iterating till it gets to the right answer.

Well not exactly. What you do is take your coordinates and convert them to a set of cartesian (x, y, z) coordinates relative to your starting datum. This is easy, there are three mathematical formulae to plug your coordinates into. You then transform your cartesian coordinates to cartesian coordinates in the ending datum. This is just a matrix multiplication - hard for a human, but easy for a computer. Then you convert your cartesian coordinates to the lat/long in the final system. This is where the "Guessing" comes in and it's the same whether your going WGS84 to OSGB36 or the other way around. In fact it's still a relatively easy process if you have a computer to help you out. One of the regular contributors (sorry I forget who it is) here has done it in Excel.

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jeremyp

We're going to need a bigger boat!

March 27, 2002

quote:
Originally posted by Chris n Maria:
I've been spending quite a lot of time looking at the OS site lately and read some very dull publications with huge formulas in them. The conclusion I have come to is that you won't find a map based on WGS84 of the UK....I could be wrong but here is what I think I have worked out.

Actually, I found all that stuff quite interesting Last time I went sailing I noticed that all the navigational charts we had were WGS84 except for the ones around Cornwall. I guess they were going through a process of converting from OSGB to WGS84 at the time.

As almost all mapping data of the UK comes from the OS and they aren't changing just yet, your comment is probably right, but for most purposes irrelevant, you just make sure your GPSr uses the right datum.

quote:
Heights add another level of complexity as they are relative to a complex mathematical shape known as the Geoid for WGS84 but OS was originally based against Mean Sea level in Newlyn at cornwall. Aparentley sea level round the UK is below sea level - Go figure!

The mean sea level at Newlyn only defines the zero for heights on OS maps. Heights in the UK still use the geoid which is defined as a surface with a constant gravitational field. If you map out a level surface it *will* be parallel to the geoid which varies depending on the density of the Earth's crust. A datum such as WGS84 is essentially arbitrary (we can put the prime meridian anywhere). The geoid depends on the physical characteristics of the Earth.

quote:
Conversion between the 2 systems is a non-trivial operation which in the case of OS to WGS84 involves Guessing the co-ords and iterating till it gets to the right answer.

Well not exactly. What you do is take your coordinates and convert them to a set of cartesian (x, y, z) coordinates relative to your starting datum. This is easy, there are three mathematical formulae to plug your coordinates into. You then transform your cartesian coordinates to cartesian coordinates in the ending datum. This is just a matrix multiplication - hard for a human, but easy for a computer. Then you convert your cartesian coordinates to the lat/long in the final system. This is where the "Guessing" comes in and it's the same whether your going WGS84 to OSGB36 or the other way around. In fact it's still a relatively easy process if you have a computer to help you out. One of the regular contributors (sorry I forget who it is) here has done it in Excel.

-------

jeremyp

We're going to need a bigger boat!

1.4k · March 27, 2002

quote:
Originally posted by jeremyp:One of the regular contributors (sorry I forget who it is) here has done it in Excel.

That'll be me then

Chris

"We're not lost - we just don't know where we are"

London & UK Geocaching Resources

1.4k · March 27, 2002

quote:
Originally posted by jeremyp:One of the regular contributors (sorry I forget who it is) here has done it in Excel.

That'll be me then

Chris

"We're not lost - we just don't know where we are"

London & UK Geocaching Resources

March 27, 2002

quote:
Originally posted by Chris n Maria:
I've been spending quite a lot of time looking at the OS site lately and read some very dull publications with huge formulas in them. The conclusion I have come to is ....

... remap the entire country, just for us GPS users.

Of course I could be wrong. If any surveyours are reading this - please be gentle.

So........... no map then?

Mark

----------------------

I was technical once

1.4k · March 28, 2002

quote:
Originally posted by Masher:
So........... no map then?

Recon it's unlikely

Chris

"We're not lost - we just don't know where we are"

London & UK Geocaching Resources

April 2, 2002

Hi Peeps..

Back to the original question. I have been in touch with Ordinance Survey and this is the Pucker Gen..

On all OSGB maps, 1:50000 etc. The grid reference system is based on OSGB36 datum where as the Lat/Long on the edges of the maps is in WGS84 datum..

There yer go.. That IS the word.

Moss de Boss... Sorta

April 2, 2002

Thanks Monz.

S'pose I'd better go find out the difference between WGS24 and OSGB36 and MFI47 now.

Mark

----------------------

I was technical once

April 2, 2002

Thanks Monz.

S'pose I'd better go find out the difference between WGS24 and OSGB36 and MFI47 now.

Mark

----------------------

I was technical once

April 2, 2002

errrrrrr..

You gona get yer personalities right never mind de maps

Moss de Boss... Sorta

April 2, 2002

errrrrrr..

You gona get yer personalities right never mind de maps

Moss de Boss... Sorta

1.8k · April 3, 2002

Maps - half the fun of geocaching for me is using good maps. But then I worked for 40 years as a surveyor - albeit a valuation surveyor but love of maps was what got me into the game!

April 3, 2002

I agree with "jstead" , I think its important to have a good working knowledge of maps, to be able read, decipher and understand a map (and then use the GPS information to supplement the map). I can spend hours just looking at a good map trying to imagine the terrain and ground conditions, and even though I have a Vista, it falls a long way short of a good map.

April 3, 2002

quote:
Originally posted by Moss Trooper:
errrrrrr..

You gona get yer personalities right never mind de maps

Moss de Boss... Sorta

Oops! Sorry Moss!

Mark

----------------------

I was technical once

April 3, 2002

quote:
Originally posted by Moss Trooper:
errrrrrr..

You gona get yer personalities right never mind de maps

Moss de Boss... Sorta

Oops! Sorry Moss!

Mark

----------------------

I was technical once

April 4, 2002

Personally I find the streetmap.co.uk ones to be pretty good for this sort of thing.

e.g. Here

It'll get you pretty close regardless and certainly let you know what sort of landscape you'll be encountering when you arrive. So you can be ready for the trees and other GPS-confusing obstacles.

Eddie

April 4, 2002

quote:
Originally posted by dawnrazor:
Personally I find the streetmap.co.uk ones to be pretty good for this sort of thing.

e.g. http://www.streetmap.co.uk/streetmap.dll?grid2map?X=450995&Y=314910&arrow=Y&zoom=3

It'll get you pretty close regardless and certainly let you know what sort of landscape you'll be encountering when you arrive. So you can be ready for the trees and other GPS-confusing obstacles.

Eddie

Indeed, I always tend to run off a copy of the Streetmap page (from the links that Rob and Lisa have on their page usually ) although I quite often take along a copy of a map with the OS 1:25,000 mapping as well as I find the detail on that a lot more useful. It's a pity that that mapping isn't available online.

A slightly stupid question here, has anyone any idea which mapping Garmin is negotiating for? (I'd say with 99.9% certainty that it will be the 1:50,000)

Richard

April 4, 2002

quote:
Originally posted by dawnrazor:
Personally I find the streetmap.co.uk ones to be pretty good for this sort of thing.

e.g. http://www.streetmap.co.uk/streetmap.dll?grid2map?X=450995&Y=314910&arrow=Y&zoom=3

It'll get you pretty close regardless and certainly let you know what sort of landscape you'll be encountering when you arrive. So you can be ready for the trees and other GPS-confusing obstacles.

Eddie

Indeed, I always tend to run off a copy of the Streetmap page (from the links that Rob and Lisa have on their page usually ) although I quite often take along a copy of a map with the OS 1:25,000 mapping as well as I find the detail on that a lot more useful. It's a pity that that mapping isn't available online.

A slightly stupid question here, has anyone any idea which mapping Garmin is negotiating for? (I'd say with 99.9% certainty that it will be the 1:50,000)

Richard

April 4, 2002

quote:
Originally posted by Moss Trooper:
errrrrrr..

You gona get yer personalities right never mind de maps

Moss de Boss... Sorta

Anyway... Miss Trouper, aint you paid your dues yet... tight fisted so 'n' so

April 4, 2002

quote:
Originally posted by Moss Trooper:
errrrrrr..

You gona get yer personalities right never mind de maps

Moss de Boss... Sorta

Anyway... Miss Trouper, aint you paid your dues yet... tight fisted so 'n' so

April 4, 2002

Too busy findin stuff put bout maps..

Moss de Boss... Sorta

April 4, 2002

Too busy findin stuff put bout maps.. :):D:D:D:D:D:D:D:D

Moss de Boss... Sorta

April 4, 2002

So right! Maps and GPS are not mutually exclusive. I've just spent two days in the NW Highlands, walking: both map and GPS have their part to play. Similarly with Geocaching. And maps are fascinating. However, Lewis Carrol wrote a story where map-makers got so ambitious with map-scales that maps became miles wide - eventually they did away with maps altogether and used the country as a 1:1 map of itself.

The nearer your destination, the more you keep slip sliding away.

Maps

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