formats available

Formats available

Introduction

Data can be downloaded from Digimap in a number of different formats. The table below shows different formats available for each product. Further information on data types is available.

Formats Available

Town Plans 1848-1939	TIFF
Original sheets	X
National Grid tiles	X

County Series 1846-1969	TIFF
Original sheets	X
National Grid tiles	X

National Grid 1943-1996	TIFF
National Grid tiles	X

When you download historic map data, you will get the following types of data:

TIFF 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 images are 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 images are 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.

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 TIFF World File which is used by ESRI GIS software (e.g. ArcGIS) to place the TIFF map image in the correction geographic location. The TFW file should always have the same file name suffix as the TIFF image it relates to (e.g. example1.tif and example1.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 TIFF 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 TIFF map image in the correction geographic location. The TAB file should always have the same file name suffix as the TIFF image it relates to (e.g. example2.tif and example2.tab) and should always be stored in the same folder as the TIFF image it relates to. It is essentially the MapInfo equivalent of the ESRI TFW World File.