Series 6 Ordnance One inch maps


There was a hiatus in civilian mapping from 1939-1945. The Sixth Edition was essentially the Survey of 1930-35 revised for 1945+. A new survey had been planned but its plates were destroyed when the Southampton offices of the OS were bombed- so this 1945+ series returned to a previous set of surveys. The lost survey plates had not been photographically recorded.

It is said that the masters used for Series 6 map were still electrotype engraved for those maps north of Birmingham but the masters were already lithographic for those Series numbers south of that rough line across the English Midlands. The 6th Series itself was entirely lithographic.

The standard dates are 1930 revision -1946 edition

The earliest and latest dates seen are about

1928 revision- 1948 publication.

Some were published in the War : 1940+. These must have had restricted sales

In this series, RAF and RNAS airfield from the 2nd World War are redacted. Royal Dockyards tend to be simply redacted and left white and blank. Army camps tend to be marked because they were visible on pre war maps anyway. Sea Plane stations were redacted.

One might have imagined that post 1945 these could again have been included but it was probably a matter of timing- also, operational RAF and RNAS fields were to remain hidden even onto the Series 7 maps.


This was the last survey to show the full Pre-British Railways’ network, with the Old Company named written by the lines. The country was covered by the Southern Railway, London & North Eastern Railway, Great Western Railway, and London Midland and Scottish Railways. Some smaller railways remained, notably “Lancashire and Cheshire Lines”, “Midland and Great Northern Joint Railway”, “Norfolk and Suffolk Joint Committee Railway”.

Here was the last survey to definitely show all the branch railways of the district open, prior to the mass closures of the 1950’s- 1960’s.


Series 6 maps named roads with their MOT numbers for the first time on 1 inch maps. This was the last survey to never show Britain motorways.

A roads showed MOT numbers and were red between black base plate lines. B roads had MOT numbers and were orange-yellow between black base plate lines. Other roads were just shown with parallel black lines on the base plate.


Woods are quite a yellow green and symbols show coniferous or deciduous. Orchards had regular tree symbols and are uncoloured. Park land was stippled- perhaps the last remnant of the electrotyped maps of old. Rough Pasture and marshes were shown with a black stippled symbil. Fields were not surveyed. Arable is not differentiated from pasture and a hop garden is not marked as an orchard, but as open land


Series 6 maps tended to be about 27 inches by 31 inches. Then were sold on cloth or paper. They were not dissected and mounted in sections unless seen as a bespoke preparation for libraries or by cartographic suppliers such as Edward Stanford.

Covers were 8 ¼ inches by 5 inches. Some early ones are shorter and fold the bottom margin in-to accommodate the same sized sheet.

There were 190 maps in the Series, numbered north to south. No 1 was Shetland; No 190 was Truro.

In Series 6 Scottish Maps were still separate from English and Welsh and has different covers- Both were called “1 Inch New Popular Edition” The numbering of the Scottish Series was different. On the index mapo, printed on the back cover, one sees Scottish sheets numberes in Red 1 to 92 and English and Welsh maps numbered 71 to 190 in black on the Index Map. English series No 64 is an oddity. It showed Berwick. But is remote in numbering from the rest of the English Series. Scottish map 64 was Dundee.

Therefore maps 71 to 92 were found in both Series as different maps. Maps 1-70 were Scottish maps alone and 93-190 were English or Welsh maps alone. The Isle of Man is No. 87 in the English Series.

Paper was not bleached to white and was not gloss. Larger places were names in Roman Serif and smaller places were Italic and capitalised only on their first letters. District or Parish names were an Italic Roman.

There was no shading – either relief of topographic, though close contours form an effective form of relief shading in fell districts. Welsh place names defaulted to the common usage of the region : Afon or River, etc.


The average map showed 40 km x 45 km or 1800 km squared. This was roughly 25 miles by 30 miles or 600 miles square.

The point 00 or “False Datum” for the National Grid was south west of the Scilly Isles. It thus allowed all Britain to be east or north of that datum. The only exception was Rockall. Ireland was a different survey.

The grid divided the archipelago into 69 100 km squares numbered 1-69. Being asymmetrical, some of these 100 km squares contained no land: 00 ,01, 02, 03, 0-4, 05, 06, 07, 09, 13, 14, 15, 49, 56, 57, 58, 59, 60, 64, 65. 66, 67, 68, 69. Others hardly touched land: 11, 47, 50, 55. Interestingly very few showed no coast water: 43 & 42. Nos 32, 44, 52 showed almost none, and perhaps the only square to show no tidal water was 43.(100 km square No 43- not Map 43).

Some important points on the National Grid were: 500-500: near Flamborough; 199-900, just off Harris; 500-100 near Portsmouth; 200-200 near Pembroke. 400-400: a reasonable Centre of England: inland from Liverpool or Skegness, due north of Poole. Very little of Scotland was east of the E400 line. The E600 is a good approximate for the Greenwich Meridian. London is centred quite near 550-180.

This series was, despite its grid, a “1 inch Series” which was 1/63360. On it One Centimetre represented 0.6336 of a kilometre.

The projection used was a Transverse Mercator. This differs from a Standard Mercator, on which latitude is correct at the Equator, by having two latitudes which are precise- roughly at the tropics and thus the world between those two latitudes is mapped in a compressed manner and the world north and south of them is progressively elongated to the poles. This reduces the distortion and the latitude of the British Isles- which would have been too sever on a Standard Mercator Projection.


Altitude was calculated above Mean Sea Level. By this date, that would be from the Newlyn Datum in Cornwall (LWMMT). The old Pre 1915 datum was at Liverpool. Some maps did not fully covert until the 1960’s. The difference between the two data is significant and not standard over the whole of the country. In Kent, for example, it ranged from about 0.9 ft to 1.6 ft. with the Liverpool figure being higher.

Lakes had bathymetric data in feet from water level. So altitude at the bottom would be shore line altitude minus Bathymetric depth. Such lakes were generally found in Cumberland and Wales. An artificial lake or reservoir had no bathymetric data because the water level was not constant: Examples might be Hawes Water, Thirlmere, Lake Vyrnwy or Abingdon Reservoir.

100 ft interval contours were surveyed; interim 50ft contours were observed. Contours were umber in colour

Series 6 did not revise using Aerial Photography, but the War heralded this form of cartography for Series 7.


Original Series 6 covers were vermilion and off-white with red and black lettering, the Royal Arms marked GR, the edition number was at top right and on the front cover was a cartouche map. The name was “NEW POPULAR EDITION ONE INCH MAP”.

The cover aesthetic was almost Edwardian and quite unlike that of Series 7 maps. OS did not use gloss covers then. All editions cited revision and publication dates on the cover. The covers of Series 6 maps hinged in the English and Welsh series; Scottish maps had floating covers.


The Railways of Series 6 maps were the Company Railways following the amalgamation of 1921-23. This created the G.W.R., L.& N.E.R., L.M. & S.R. and the Southern Railway. Some smaller systems survived- notable Cheshire Lines near Merseyside, the Midland & Great Northern Joint Railway in East Anglia and the Norfolk and Suffolk Joint Committee Railway in those counties.

The maps show some peculiarities of this system: At Shoeburyness in South East Essex one finds the LM&SR, not the L&NER and at Ilfracombe one finds the SR nor the GWR.

There were no preservation railways at this age. Welsh narrow gauge railways would still have served quarries. The Romney Hythe and Dymchurch Railway was marked, for it opened in 1926.

These maps do not show a completely steam railway system. The Liverpool Overhead Railway was electric from 1893; the Metropolitan and District Railway used some electric traction from 1900. The Lancashire and Yorkshire Railway began electrification in 1904. The Midland Railway began in 1908 and the LB&SCR to Brighton in 1909 but is was the Southern Railway of 1925+ which greatly increased electrification- and those would be so powered on these maps. Interestingly they used a 3rd rail where as their predecessor the LB&SCR has used overhead power.


Series Six maps do not show Admiralty soundings , as earlier terrestrial Ordnance 1” maps did. But the shallows and tidal flats were shown in great detail in a grey stipple- and the major tidal flats are named. The marine contours of a Series 6 map are 5 and 10 fathoms. Note that inland waters are measured in feet not fathoms (if measured at all). A fathom, for safety at sea, was calculated from the lowest tide, not the Mean Tide. Thus you cannot strictly calculate combined terrestrial and submarine altitude by adding on to the other. A fathom is 6 ft so the two contours on a Series 6 OS map equate to 30 ft and 60 ft sea depth. A shallow water which can be measured by plumb line is “sounding”. “Beyond Sounding” is deeper than 100 fathoms. Interestingly, burial at sea has to be at least 6 fathoms: called “Deep Six”. Technically a fathom is 1/1000 of an Imperial Nautical or Sea Mile, which is a little more than 6 ft.


1” OS maps did not show bomb or war damage- there was no new survey work between the Pre war revision date and the publication date. There might have been a couple of exceptions to the above rule, one might have been Portsmouth, where cleared streets seem to be seen near the docks. One has to fine 25” or 50” surveys- used by the Land Registry and Planners before the word “ruin” is seen on buildings, plots and parcels of land.

Urban blocks of buildings were, on Series 6 maps, represented with opaque black. This is the first full lithographic series. Previous editions of the 1” survey used hatching on urban areas, as is necessary with an intaglio, engraved or electrotyped process. The aesthetic result is that this Series 6 seemed bolder, darker and broader lined than that which preceded it. The electrotypes were light, high key and thin lined. This use of black for urban areas was short lived and somewhat problematic. By the 1950’s it had been replaced with lithographic grey in which individual buildings such as town halls and churches could again be differentiated, in black, from the general urban shading.