Pete
For a comprehensive bibliography of OS maps, revisions etc., Richard
Oliver's Ordnance Survey Maps: A Concise Guide For Historians (Pub. the
Charles Close Society for the Study of OS Maps) 1993, reprint with corrs.
1994, will help in 98% of cases. The Survey's history of Lancaster's mapping
from 1845 is covered on p. 99; for Lancashire, equally useful, from 1838 see
p. 148.

Hal Bishop
Archaeology Officer
Torbay Council
01803-207788

        -----Original Message-----
        From:   Iles, Peter [SMTP:[log in to unmask]]
        Sent:   Wednesday, February 05, 2003 10:18 AM
        To:     [log in to unmask]
        Subject:        Re: Digital Historic OS maps - Advice wanted

        Digital Historic OS maps - There is a better way than Landmark Ltd
in our
        experience, but it might not be classed as 'cheaper', but it depends
on what
        you want.

        Problems with the Landmark data include 

        1) that they have cut up and tiled the original sheets to 5km x 5km
squares,
        equivalent to the 1:10,000 'quarter sheets' and on any one of these
tiles
        you may have sections of one, two or four original maps with
different
        publication and survey dates - it also make referencing back to the
original
        map a real pain.  

        2) They have also been scanned from the OS holdings of these maps,
WHICH ARE
        NOT NECESSARILY THE FIRST VERSION OF THE MAPS PRODUCED AND MAY BE
REVISED
        MAPS PRODUCED 20-40 YEARS AFTER THE QUOTED 'PUBLICATION' DATE.
Sorry to
        shout there but I've tried to get them to acknowledge this problem
on their
        'oldmaps' web site and to let people know about this - it can be
very
        misleading.  The changes to the maps were generally things like
railways and
        properties immediately adjacent to the Rwy such as mills, but I have
also
        found other changes but the important point is that it is not
usually noted
        on the map that it is a revised version. To look at this try their
'oldmaps'
        site and look at Lancaster city centre and then compare it with the
same
        area on our website http://mario.lancashire.gov.uk which is a
web-based GIS
        and has the 'real' first ed. 1:10,560 and some 1:2,500 maps on it -
you will
        spot a number of extra railways built in the 1850's on the 'oldmaps'
image,
        even though they claim a publication date of 1848! They claim that
as this
        date is on the map, then that is they date they should quote,
despite it
        being 'wrong'.  The revised maps are referred to as 'first state',
'second
        state', etc. and as far as I know, no one has produced a
comprehensive
        bibliography of these - please let me know if you know different.

        3) The image quality is very variable, in some places they are
unreadably
        black, in others so light that most lines have dropped out

        4) They are only available as monochrome images.

        5) The licence agreement is very restrictive

        Solutions - don't buy from Landmark, digitise your own!
        We borrowed a set of the 1:10,560 first edition sheets and a
selection of
        1:2,500 first edition sheets (in batches) from our County Record
Office,
        carefully selecting the cleanest copy and checking for the revision
problem
        mentioned above and asked a commercial company to scan them and
rectify them
        to the modern OS grid for us.  They were then supplied as 400dpi
monochrome
        images (TIF) and 200dpi greyscale images (JPG) on CD-Rom with the
        appropriate GIS world files.  Cost was £90 per sheet, but they would
produce
        the mono-only sheets for £60.  You could get them scanned a lot
cheaper than
        this, it is the processing and rectification that takes time and
money, but
        if you have the time/equipment/software you can do it yourself -
Erdas
        Imagine is the software of choice for this but it's not a trivial
job.  As
        far as we understand the digital maps are then your copyright, to
        use/distribute/display/sell as you want. 

        If you want the name of the firm that did our maps, or to chat about
it
        more, email me on [log in to unmask]


        Pete Iles, Lancs SMR






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