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    Re: An essay about maps
    From: John Huth
    Date: 2010 Nov 14, 10:21 -0500
    Peter - 

    This is all preaching to the choir, I suppose.  Most folks on this list probably know how far one can trust a map, but I do appreciate you sending around the column that woman wrote.

    I might add an addendum to the various thoughts, and even a response to her essay that I suppose will never reach her, but it's something like this:

    Consider what it takes to create a map.   You have to start with a well-surveyed control network.   In the modern era, you lay on top of that aerial stereo photographs to get the major topographic features.   Then you have whatever local knowledge you can put on top of that to extract paths that may be hidden from view in the aerial photographs.   Presumably paved roads have blueprints that lay out their path relative to the control network.   All of this is a lot of work.   I know some land surveyors and they'll tell you how difficult it is to find some markers on the secondary control networks.   Sometimes, it's a half buried bottle hidden by a bush.   In the particular case of the missing dirt track, washouts happen all the time, and some aspects of the landscape change far faster than surveyors and cartographers can keep up with it.  

    All of these are good reasons to consult the date of creation of the map and the revision history.

    Now that I think about it, I have to grab some maps myself.   Has anyone on this list been to Rollright?   Know anything about astronomical alignments of it (or lack thereof?).   I'm visiting there in a couple of weeks and am trying to sort through the literature.   Talk about reverse engineering - going back 10 years is one thing, but 4500 is quite another.

    John H. 

    On Sun, Nov 14, 2010 at 4:39 AM, Jackie Ferrari <jferrari@clara.co.uk> wrote:
    I have used them extensively hiking around the Highlands of Scotland. Once looking for a particular forest in which to camp, I was convinced my navigation was wrong as I could see no forest where my 1:50000 Ordnance map told me it should be. Nonetheless I kept on the path(a sheep track) and lo and behold ,there it was. A plantation of 6 inch high conifers.
     However on occasion, forest tracks marked on the map are no longer there, but these have always been man made tracks, made by bulldozers for clearance. It seems the sheep tracks are more 'permanent.' !
    ----- Original Message -----
    Sent: Sunday, November 14, 2010 4:07 AM
    Subject: [NavList] Re: An essay about maps

    Certainly, the USGS topo's are far out of date with respect to tracks - hiking and passable 4-wheel-drive routes.  I've found too many out of date instances to recount.

    On Sat, Nov 13, 2010 at 6:00 PM, Fred Hebard <Fred@acf.org> wrote:
    Are the British Ordnance Survey maps really as accurate as she claims?  I've never seen a high resolution (<= 30') map that was 100% accurate, where I had knowledge enough of the terrain to detect the errors.

    It was rather a nice read, thanks for sharing it.

    On Nov 13, 2010, at 4:43 PM, Peter Fogg wrote:

    An essay for those interested in maps:

    You can tell the good lady is from the Big Smoke.  If she'd spent more time in remote places she'd have known that when you get to a place like Hungerford you don't just drive through it.  You stop and, first of all, take on fuel.  Even if your tanks are near-full - whether you'll find any more further on is never guaranteed, and the person selling fuel is potentially a good source of information about what lies ahead.  Then you visit the pub.  If the place is a stepping-off point to really remote places you're also expected to register with the cops.  Its just common sense really, but you can expect to be quizzed about how well-prepared you might be for the next leg, including your mapping resources.

    As you drive out from the relatively well-populated coast into the relatively bereft-of-people interior, you go from ignoring other motorists to acknowledging them.  Then when you get further out, if another vehicle approaches from the direction you're going then you both stop - blocking the road, but that's rarely a problem - so the drivers can have a leisurely chat, driver's window to driver's window, elbow to elbow, about the weather and the price of ewes and, what interests you most, what's ahead.

    In two words: local knowledge.  The good lady is dreaming with her whimsical insistence on mapping accuracy.  As if there was such a thing.

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