tag:blogger.com,1999:blog-5239363389942831054.post5350597769378245668..comments2010-01-06T12:15:09.626+00:00Comments on EDINA Digimap: Publication dates for historic mapsEDINA Digimap Supporthttp://www.blogger.com/profile/01840955178628191268noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-5239363389942831054.post-70009612534459418652008-10-15T11:27:00.000+01:002008-10-15T11:27:00.000+01:00There may be some confusion here. There are sever...There may be some confusion here. There are several scales of maps which have been scanned from paper originals and are now provided through Historic Digimap. The two primary scales are 1:2500 and 1:10,560 for the pre-WWII County Series mapping. Post-WWII there are 1:1250, 1:2500, 1:10,000 and 1:10,560. For the smaller scale, this overlap in scales and dates represents the period during which the national surveys were undertaken. In the Historic Digimap Help pages there is a lengthy extract about map scales and characteristics from Dr Richard Oliver's book, "Ordnance Survey Maps: a concise guide for historians" which gives greater detail. The scale of each Series is also given in the drop-down lists of maps in the Historic Digimap mapping interface. Each "Edition" has its scale clearly quoted in the heading.<BR/><BR/>Since all of these are delivered as digital images, they can be displayed at any scale the user chooses if appropriate software is available. Clearly the quality of the image will vary significantly depending on the display scale. Some of the "cookie cut" versions (those which have been rectified to match the National Grid) have .tfw files delivered with them already, so you shouldn't need to create your own for these data files. A world file is a plain ASCII text file consisting of six values separated by new lines. Wikipedia has a detailed explanation of the file format: http://en.wikipedia.org/wiki/World_file.EDINA Digimap Supporthttps://www.blogger.com/profile/00397934115623604248noreply@blogger.comtag:blogger.com,1999:blog-5239363389942831054.post-79989571041321926262008-09-04T10:43:00.000+01:002008-09-04T10:43:00.000+01:00I would like to add that the historic digimap rast...I would like to add that the historic digimap raster tiles are at a scale of 1:10,000 and not 1:10,560. I don't believe this is stated anywhere. Whilst for most people it is not a problem. it does become a problem if you are trying to figure out how one creates a world coordinate file and you attempt to use the maps original scale of 1:10,506, in your calculations.Anonymousnoreply@blogger.com