SABRE Maps/Half Inch coverage project
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Fifth Edition • New Popular Edition • Scottish Popular • Seventh Series • Half Inch • Ministry of Transport • Quarter Inch • Ten Mile & Route Planning
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Adding maps in depth
Map layer names
This project is to provide online coverage of the various OS, OSI and OSNI maps at the Half-Inch scale to SABRE Maps, focussing primarily on those maps that include road numbering on them, although coverage of OS Ministry of Transport Road Maps are detailed elsewhere due to their extreme historical importance.
Maps at the half-inch scale are unusual in Ordnance Survey GB, and most familiar to us because the MoT maps are based on (old) Half-Inch outline maps with the coloured overlays, which is why then-new bypasses look a bit odd sometimes, because there's no road underneath the overlay. They started to fall out of favour around World War 1, though some sheets continued into the late 1920s and early 1930s before being cancelled, though there are some "District" sheets that continued to be produced until just after World War 2. These District sheets are invaluable to us, as they contain road numbering at a more detailed scale than Quarter Inch maps, usually in areas where there was no One Inch Fifth Edition coverage. Bear in mind that the older Half Inch series confusingly comes in covers called Ordnance Survey Road Map, but these are based on the pre-World War 1 series with no road numbers printed on them, and are not the same thing as either the OS Ministry of Transport Road Maps or the later National Yard Grid district maps - both of which do contain road numbering information.
There was an attempt to bring back OSGB maps at the Half-inch scale across the whole of Great Britain in the late 1950s and early 1960s, but there were only ever five maps produced at that scale (and one further to proof stage), plus one Tourist Map before once again the series was cancelled, and there's been no real attempt since 1962 to publish a series of maps at this scale in Great Britain.
However, in Ireland it's a different story. Half inch maps produced by both OSI and OSNI were common through to the late 1980s, and relatively large numbers have survived - meaning that they're a valuable resource for us to have.
- 1 Which projection type are these maps?
- 2 How do I find out the date of the map?
- 3 Ordnance Survey Half-Inch
- 4 Ordnance Survey Ireland 1945-1970
- 5 Ordnance Survey Ireland District maps
- 6 Ordnance Survey Northern Ireland Half-Inch Second Series
Which projection type are these maps?
Maps at the Half-Inch scale use various projections, and so care will be needed to select the correct one.
English OS Half-inch maps of the 1930s and 1940s use the National Yard Grid, even if it is not specifically printed on that revision; whilst Scottish sheets of that time use the Bonne (Scotland) projection. All post-1950 sheets of Great Britain use the OSGB National Grid.
Post-1955 OSI Half-inch maps have Irish Grid references printed on them, but in common with earlier maps they actually use the Bonne (Ireland) projection. Georeferencing using the Irish Grid on these maps will result in poor alignment and the full map area not being available.
In comparison, the OSNI Second Series maps really do use the Irish Grid, and should be georeferenced accordingly.
How do I find out the date of the map?
Annoyingly, Ordnance Survey GB didn't actually put the exact date of the map on each map. The date that appears on the map (usually with the words First published by the Director General at the Ordnance Survey Office) often is not the correct date of the map, but the date of the first revision of the map. Roads, along with other minor corrections were actually updated on every revision, so the map you have may be from a number of years away from the most obvious date.
Revision codes on OS GB Half Inch sheets can be found in one of two places. In the maps from the early 1930s, they are located right at the bottom right of the map sheet, underneath the margin texts; whilst in most sheets, they are located immediately under the bottom left corner of the maps themselves, between the map and the key. Just occasionally they're located immediately under the bottom left of the key.
Irish maps on the other hand, generally have some of the simplest revision code information to find - they're generally bottom right just underneath the map, with extensive dating information to the right. Be aware that a number of early Irish Half-inch maps don't actually have specific revision codes on them, so if you have a pre-Irish Grid map, and there isn't one in the right location, then there probably isn't one at all!
Second Series Ordnance Survey of Northern Ireland half-inch sheets however have a very similar lettering system to OSGB maps, again bottom left just underneath the map itself. However, it appears that OSNI only ever printed one edition of each of the four sheets.
Revision codes are the best way of dating the maps, and so this information is extremely valuable to capture. On SABRE Maps, where we have it the revision code appear in the sheet name heading area.
Which maps are actually available?
If two revisions were printed in a single year, then the one nearest to the centre of the year is listed as being from that year, and the other revision shifted into the earlier or later year as appropriate. Only standard civilian colour editions are listed.
Only Second Series and other maps believed to contain road numbers are included.
The dating of the map revisions is taken from the Charles Close Society Half Inch Cartobibliography.
Key to tables
|Available on Maps||Unconfirmed Revision||Within the pipeline||Not currently available||Still within copyright|
Ordnance Survey Half-Inch
National Yard Grid maps
|-||Island of Skye||4000/32||30/37|
Note: the Island of Skye map is technically not a National Yard Grid map, but is instead on the Scottish Bonne projection. It is, however, visually similar to the remainder, and from the same period.
National (Metric) Grid maps
Note: Sheet 37 (Leicester) was never released, but a proof copy exists, and was republished by the Charles Close Society in 2012. Their re-publication is therefore still within copyright and cannot be used without permission.
Ordnance Survey Ireland 1945-1970
OSI Half-Inch sheets regularly changed their names, but not their layouts or alignments. All names are therefore given within the "Name" column.
|no code||no code||11.55||9.57||4.61||5.64||9.67||10.69|
North Derry-North Antrim
|no code||no code||no code||6.57||8.61||11.64||11.67||12.69|
|6||North Mayo||no code||12.56||8.62||8.67|
|10||Westport and Clifden
|no code||no code||6.57||10.60||1.64||9.65||1.68||12.69|
|11||South Mayo||no code||3.57||9.61||9.65||7.68|
|no code||no code||1949||1950||11.55||5.58||10.62||8.65||1.68||9.70|
|no code||no code||11.56||8.60||8.64||9.67|
|no code||no code||6.47||6.48||5.49||7.50||1.56||1.58||10.60||4.63||1.65||9.66||8.68|
|17||Limerick, Ennis and Listowel
Mouth of the Shannon
|18||Templemore and Tipperary
|20||Killarney and Dingle Bay
|22||Cork and Lismore
|23||Waterford and Wexford
Ordnance Survey Ireland District maps
|-||Barrow and Nore Basins||9.63|
|-||Cill Dalua: Killaloe||12.64|
Ordnance Survey Northern Ireland Half-Inch Second Series