understanding names

Understanding File Names and Formats of Historic Map Data.

Introduction
County Series Original Map Sheet Names
County Series "Cookie Cut" National Grid Tile Names
National Grid Map Sheet Tile Names
Data Types: tif; tfw; tab

Introduction

This help page explains the file names given to the historic map data which you can download from Historic Digimap. There are 3 types of file name prefix (prefix.tif, e.g.34009011.tif), associated with the 3 different types of map images that are available:

pre 1945 County Series original map sheets;
pre 1945 County Series map tiles "cookie cut" to the contemporary National Grid;
post 1945 National Grid map sheets.

There are 3 types of file name suffix (filename.suffix, e.g. 34009011.tif), associated with the different types of files which are downloaded:

TIF: image files
TFW: ESRI GIS world files
TAB: MapInfo GIS world files

These file name prefixes and suffixes are described in the following sections.

County Series Original Map Sheet Names

The County Series Surveys carried out before the Second World War were not National Surveys or projected to the National Grid as with all modern Ordnance Survey mapping. Each County (or sometimes groups of neighbouring Counties) were surveyed separately with their own survey origin and sheet lines using the Casini Projection.

Consequently the way the County Series maps were named is different from the naming conventions used for all contemporary Ordnance Survey maps. The naming conventions used for the original maps are used by Landmark Information Group as the basis for the associated data files available for download via Historic Digimap.

County Series Original Map Sheet data files are named to the following convention:

34009011

The first 2 digits refer to the County: 34 = Surrey (see table below for a list of County Codes)
The next 3 digits refer to the Block Number: 009 = Block 9
The next 2 digits refer to the Sheet Number: 01 = Sheet 1
The final digit refers to the Edition: 1 = First Edition

In the case of 1:10,560 maps the sheet number is replaced by one of the following: NW, NE, SW, SE, or 00, depending on it being a quarter or full sheet.

Ignoring the first two and the last digit, of each file name, will leave you with the original OS Map Name, e.g.:

file name 34009011 becomes 009/01 (1:2500 County Series Map Sheet)
file name 34009NE1 becomes 009/NE (1:10,560 County Series Map Sheet)

County Codes Used by Landmark in County Series Map Sheet Names

01 Bedfordshire
02 Berkshire
03 Buckinghamshire
04 Cambridgeshire & Isle of Ely
05 Cheshire
06 Cornwall & Isles of Scilly
07 Cumberland
08 Derbyshire
09 Devon
10 Dorset
11 Durham
12 Essex
13 Gloustershire
14 Hampshire &Isle of Whight
15 Herefordshire
16 Hertfordshire
17 Huntingdonshire
18 Kent
19 Lancashire and Furness
20 Leicestershire
21 Lincolnshire
22 London
23 Middlesex
24 Norfolk
25 Northamptonshire
26 Northumberland
27 Nottinghamshire
28 Oxfordshire
29 Rutland
30 Shropshire

31 Somerset
32 Staffordshire
33 Suffolk
34 Surrey
35 Sussex
36 Warwickshire
37 Westmorland
38 Wiltshire
39 Worcestershire
40 Yorkshire
41 Anglesey
42 Brecknockshire
43 Caernarvonshire
44 Cardiganshire
45 Carmarthenshire
46 Denbighshire
47 Flintshire
48 Glamorganshore
49 Merionethshire
50 Monmouthshire
51 montgomeryshire
52 Pembrokeshire
53 Radnorshire
54 Aberdeenshire
55 Argyllshire
56 Ayrshire
57 Banffshire
58 Berwickshire
59 Buteshire
60 Caithness-shire

61 Clackmannanshire
62 Dumbartonshire
63 Dumfriesshire
64 Edinburghshire
65 Elginshire
66 Fifeshire
67 Forfarshire
68 Haddingtonshire
69 Inverness-shire & Skye
70 Kincardineshire
71 Kinross-shire
72 Kirkcudbrightshire
73 Lanarkshire
74 Linlithgowshire
75 Nairnshire
76 Orkney
77 Peebleshire
78 Perthshire
79 Renfrewshire
80 Ross & Cromarty
81 Roxburghshire
82 Selkirkshire
83 Stirlingshire
84 Sutherland
85 Wigtownshire
86 Zetland (Shetland)
87 Outer Hebrides
88 Isle of Lewis
89 Isle of Skye
90 Isle of Man

County Series "Cookie Cut" National Grid Tile Names

To make the pre World War II County Series maps more easily comparable to modern National Grid maps and to allow the creation of seamless coverages in GIS, Landmark Information Group have processed the original County Series map sheets to create National Grid tiles. This was done by merging neighbouring sheets and then "cookie cutting" the original maps to an overlaid National Grid. So any one derived National Grid tile could contain parts of up to eight original County Series map sheets. More information on how this was done is available in the following Historic Digimap Help page: How Landmark digitally captured the paper historic maps.

The resulting National Grid "cookie cut" tiles are named using Ordnance Survey's National Grid naming conventions with a two character prefix relating to which Historical County the data originated from (this prefix relates to those codes listed in the County Code table, above, and correspond to those used in the naming of the original map sheets).

For example: 05SJ3965

05 = County Name, in this case Cheshire
SJ3965 = OS National Grid naming Convention

National Grid Map Sheet Tile Names

The post World War II National Grid maps and TIF data files available through Historic Digimap are named using the Ordnance Survey's National Grid naming conventions, in the same way as all contemporary O.S. maps.

1:2,500 files use the following convention:

TL1234
The first 2 digits refer to the National grid block: TL = 52
The next 2 digits refer to the easting: 12 = 12
The final 2 digits refer to the northing 34 = 34

1:1,250 files are named in the same way as the 1:2,500 files, except that one of the following is added to the end of the file name:

NW, NE, SW or SE (i.e. TL1234NE).

1:10,560 and 1:10,000 files use the following convention:

TL12NEM5

The first 2 digits refer to the National grid block: TL = 52
The next digit refers to the easting: 1 = 1
The next digit refers to the northing: 2 = 2
The next 2 digits refer to the quad: NE = NE
The final 2 digits refer to the edition: M5 = Metric Edition 5.

The following 1:10,560 (Imperial) editions are available:

I5, I6, I7, I8

The following 1:10,000 (Metric) editions are available:

M5, M6, M7

Data Types: tif; tfw; tab

When you download map data using the Historic Digimap Download Data tab, you will get the following types of data (identified by the file prefix, e.g. TL12NEM5.TIF).

.TIF files

The TIFF map images available for download from the Download map data tab are as provided by the Landmark Information Group. All map images were supplied as CCITT Group 4 TIFF format. However, there are two varieties of Group 4 TIFF:

Banded TIFF

This type of TIFF image is read in lines, or bands, across the whole image, until the image is completely displayed. This is the most common type used for general image data.

All the post 1945 National Grid map tile images and pre 1945 County Series National Grid cookie cut images available for download from Historic Digimap are in Banded TIFF format and can be read by a wide selection of image viewing software and GIS

Tiled TIFF

This type of TIFF is read in square blocks, until the image is completely displayed. Tiled TIFF is more suitable than Banded TIFF for large images as only the blocks which will appear in the display need to be read. This is the preferred format for GIS use.

The Original County Series Map Sheet images (i.e. not those cookie cut to match the modern National Grid) available for download from Historic Digimap are in Tiled TIFF format. They can be read by GIS software (e.g. MapInfo and ESRI ArcGIS) but only a few image viewing or processing applications.

Of those tested, the following image viewing applications will read and display the Original County Series Map Sheet Tiled TIFF images:

Gimp (Freeware for Mac, Windows XP or Linux, downloadable from http://www.gimp.org)
Adobe Photoshop 7 (Mac and PC)
Apple Mac Preview (OSX)

The following common image viewing software will not open the Original County Series Map Sheet Tiled TIFF images:

Microsoft Windows XP Picture and Fax Viewer (default viewer when double clicking on an image in Windows Explorer)
Microsoft Paint
JASC Paint Shop Pro
Macromedia Fireworks
Macromedia Freehand
Adobe Illustrator
Corel Draw 12
Corel Photo Paint 12

Note that the post 1945 National Grid map images and the Pre 1945 County Series map images cookie cut to the match the National Grid can be viewed in all of the above applications. All TIFF images, regardless of whether they are Banded or Tiled format can be read and displayed in MapInfo GIS or ESRI ArcGIS.

.TFW files

A .TFW file is a TIF World File which is used by ESRI GIS software (e.g, ArcGIS) to place the TIF map image in the correction geographic location. The TFW file should always have the same file name suffix as the TIF image it relates to (e.g. TL12NEM5.TIF and TL12NEM5.TFW) and should always be stored in the same folder as the TIF image it relates to (otherwise, ArcGIS would not find the world file when you add the TIF image, so will not know the geographic extent and position of the map image). The TFW file is a plain text file which can be opened in any text editor.

.TAB files

A .TAB file is a MAPINFO GIS Table data file which contains coordinate information used to place the TIF map image in the correction geographic location. The TAB file should always have the same file name suffix as the TIF image it relates to (e.g. TL12NEM5.TIF and TL12NEM5.TAB) and should always be stored in the same folder as the TIF image it relates to. It is essentially the MapInfo equivalent of the ESRI TFW World File.