 Figure 1 Explorer sheet 1 (Mar 1994) |
 Figure 2 Explorer sheet 5 (Mar 1994) |
 Figure 3 Explorer sheet 7 (Apr 1995) |
Thus the ‘Explorer’ series was launched in March 1994 with the publication of sheets 1 to 5. These sheets were mainly constructed from exact combinations of 1:25 000 Second Series sheets (the one slight exception being Sheet 2 Chiltern Hills North which was a combination of 2 full sheets and 2 half-sheets), incorporating minor revisions and using the same simple colour scheme. Sheet 3 Chiltern Hills South was the only sheet of the five to be double-sided.
The Explorers’ covers followed the style of the time, with a cover photo, sheet title in white and the Ordnance Survey logo in a box. The orange colour distinguished the Explorers from the other series with similar covers. (Figures 1, 2). Their Pathfinder origins are belied by the fact that there is no legend information printed on the maps themselves; the legend panel takes up the entire inside cover instead. This allowed the use of a cover just 222mm (8¾in) tall - almost a quarter-inch shorter than the 1:50 000 Landranger series covers.
Having had time to judge the success of the initial 5 sheets, Ordnance Survey set out on the publication of a further 26 sheets, from April 1995 onwards. These later sheets used more complex sheet lines not necessarily coinciding exactly with combinations of 1:25 000 Second Series sheets. Explorer sheets 6 to 31 also employed full-colour printing, making differing types of roads a great deal easier to identify: motorways (and waterways) in blue, A-roads in red, B-roads in orange, unclassified roads in yellow (2 shades thereof) or uncoloured, and forests & rights of way in green (i.e. much the same colour scheme as the Outdoor Leisure series). They were also issued in covers that were 240mm (c. 9½in) tall - some 18mm (c. ¾in) taller than Explorer sheets 1 to 5. (Figure 3)
 Figure 4 Explorer sheet 15 (May 1996) |
 Figure 5 Explorer sheet 31 (Mar 1997) |
In 1996 the Ordnance Survey logo was redesigned. The first published map to carry the new logo and the new ‘house style’ was Explorer sheet 15 Rutland Water, published in May 1996. (Figure 4)
A great deal had changed since the 1:25 000 Second Series had begun in 1965, and the increased emphasis on both marketing and efficiency led Ordnance Survey to consider replacing the Second Series with a series which had fewer individual sheets. By the time the last six sheets in the original Explorer series were published in the Spring of 1997 (Figure 5), it was clear that the initial 31 sheets had been a success. Ordnance Survey took the decision in late 1996 that the Explorer series should become the new national-coverage 1:25 000 map series, covering all areas of the country not published in the Outdoor Leisure series.
(For a list of the original 31 Explorer sheets, see the themed category page).
The layout of the national Explorer series was constructed largely using geographically-based sheet lines where possible, instead of purely grid-based sheet lines, i.e. for the most part not allowing important features/towns to be spread over more than one sheet. This was designed to make the Explorer series more user-friendly and therefore hopefully more popular than the previous national 1:25 000 series.
 Figure 6 Explorer sheet 150 (May 1997) Picture from Blackwell’s Online |
 Figure 7 Explorer sheet 169 (Jun 1998) |
 Figure 8 Explorer Short-format cover |
The 370 Explorer sheets are numbered (slightly haphazardly) from south-west to north-east, the first sheet being no. 101 Isles of Scilly. The sheet lines are not regular, and the area that each sheet covers is not uniform, though generally a single-sided Explorer sheet covers approximately 600km² - 650km². 144 of the 370 sheets in the series are double-sided, each covering an area of up to approx. 860km².
Sheet 150 Canterbury & the Isle of Thanet was the first of the extended series to be published, in May 1997. (Figure 6). The extension of the series meant that the original Explorer sheets (nos. 1 to 31) had to be re-numbered and, in some cases, their sheet lines were re-cast. In fact in July 1997 Explorer sheet 1 Kielder Water was replaced by a sheet in the 1:25 000 Outdoor Leisure series covering a much larger area. The re-jigging of the orignal Explorer sheets took place over the following 4½ years, concurrent with the rapid publication of new Explorer sheets. (Figure 7). Digital scanning of the source material (taken from the 1:25 000 Second Series) and extensive digital revision were among the techniques employed to ensure publication of new sheets at a much faster rate than had previously been possible.
The 144 double-sided Explorer sheets all have shorter covers than the rest of the series: they are 227mm (c. 9in) tall (identical to the Landrangers) instead of the regular 240mm (c. 9½in). The first of these to be published was sheet 129 Yeovil & Sherborne in September 1997; more soon followed. (Figure 8)
 Figure 9 Explorer sheet 179 (Dec 1999) with Millennium Products logo |
 Figure 10 Explorer sheet 135 (Jun 1999) Showing the Greenwich Meridian |
 Figure 11 Explorer sheet OL45 (Mar 2002) Formerly Outdoor Leisure 45 |
The Explorer series was awarded the ‘Millennium Products’ accolade by the Design Council on 2 April 1998, in recognition of its innovation and that it enabled “many more people to discover and enjoy Britain’s natural and cultural environment.” Ordnance Survey used the ‘Millennium Products’ logo on the covers of the Explorer series from late 1998 to mid 2001. (Figure 9)
As the start of the new millennium approached, Ordnance Survey decided to ‘cash in’ on the hype. The Greenwich Meridian (0° longitude) was seen as the focus for celebrations, being the point from which global longitude and time of day is measured. Between January and July 1999, the 17 Explorer sheets which the Greenwich Meridian crossed were published with the addition of a thick green line across the map face representing the line of 0° longitude. The covers of the maps indicated this by way of a green flash with the words “Showing the Greenwich Meridian”. (Figure 10). For details of the sheets involved, see the themed category page here.
In time it was realised that having two separate 1:25 000 series covering Great Britain was not an ideal situation; some customers were confused as to which map they required. In 2002, therefore, the Outdoor Leisure series was subsumed into the Explorer series. The resulting 33 ‘Explorer OL’ sheets carry their original numbers from the Outdoor Leisure series, with an ‘OL’ prefix. (Figure 11). For a couple of years following the change, a yellow flash on the front cover of the Explorer OL maps explained that they were formerly Outdoor Leisure sheets. A similar explanatory note was also to be found on the rear-cover sheet indexes of some Explorer and Explorer OL maps whose indexes showed ‘OL’ sheets.
All the sheets in the ‘OL’ range of Explorer maps are double-sided, covering an area of up to 1,300km² each and appearing in the regular 240mm (c. 9½in) tall cover. This increased to 177 the number of double-sided sheets in the Explorer series overall.
The roll-out of the national Explorer series was completed in March 2003 with the publication of the final sixteen sheets (nos. 455-470 inclusive) covering the northern Hebrides and the Orkney and Shetland Islands.
Since 2002 Ordnance Survey has promoted its ‘Free Maps for 11-year olds’ scheme: every pupil in Year 7 (England/Wales) or Primary 7 (Scotland) is eligible to receive a free copy of their local Explorer sheet. To date well in excess of 5 million Explorer maps have been provided free of charge to pupils through the scheme.
 Figure 12 Explorer sheet 155 (Nov 2004) |
 Figure 13 Explorer sheet OL45 (Oct 2005) |
 Figure 14 Explorer sheet 180 ‘Active’ edition (Mar 2006) |
The Countryside and Rights of Way Act 2000 legislated new powers for the public to roam on areas of so-called ‘Access Land’. These rights came into effect between September 2004 and December 2005, in stages, in 9 regions of England and Wales. Ordnance Survey, as the national mapping agency, was given the task of detailing the extent of these areas of Access Land on their maps, and chose the Explorer for the task. As each area gained its access rights Ordnance Survey planned to publish the relevant revised sheets, rebranded as ‘OS Explorer’ maps in a new-style cover. (Figures 12, 13). The photographs on the revised covers are no longer necessarily of a particular place on the map: a note inside explains that the cover photo merely illustrates the type of activity and/or landscape that can be found in the area the sheet covers.
In the event, after initially keeping up, the publication schedule began to fall slightly behind the official roll-out of Access Land areas. Publication of the ‘Access Land’ Explorer sheets for England and Wales was finally completed in April 2006. Publication of revised sheets for Scotland in the updated style, but without Access Land information, was completed in December 2007.
Ordnance Survey had been wary of weatherproof maps after several unsuccessful attempts in the 20th century. As a result from the 1990s onwards several companies created and marketed their own laminated versions of OS maps, e.g. ‘TuffMap’ and ‘Aqua3’. Wanting a slice of the action, Ordnance Survey decided to have another go and in 2006 created weatherproof ‘Active Map’ versions of the entire Explorer series. The cover and map are laminated and the map is more durable than the standard paper version. The first batch of 180 ‘Active Map’ Explorer sheets were published in March 2006, the remaining 223 being published in November of the same year. (Figure 14). They are kept up to date with each revision of the standard format version of each sheet.
 Figure 15 Cover spines of Explorer sheet 170 Top: 2006 (standard white lettering) Bottom: 2009 (erroneous blue lettering) |
During January and February 2009, the covers of a small number of Explorer sheets were erroneously printed with blue lettering on the Ordnance Survey logo on the spine. (Figure 15). To date, cover printings of six short-cover format Explorer sheets are known to have been affected. This was apparently due to a design error and also affected some sheets of the 1:50 000 Landranger Series. Rather than scrapping the affected covers and reprinting them, Ordnance Survey decided to let the stock sell through. Details of the sheets involved can be found on the themed category page.
Conclusion
The Explorer series has grown rapidly in popularity during its 14-year existence as a national series to become an invaluable accompaniment to walking and other countryside activities. The mapping is not subject to full systematic revision however - rather major changes are added ‘ad-hoc’ - thus Explorer mapping of rural areas can sometimes be rather out-of-date. Nevertheless it is the most detailed mass-produced topographic map series available covering the whole of Great Britain.
Changes on Explorer covers, 1996-2006
Many changes - subtle or otherwise - were applied to the design of the Explorer cover between 1996 and 2006. The main changes concern the top of the front cover, and are best illustrated using actual examples. Thus, the pictures and text below detail the known stages of change and their approximate production dates.
 May 1996 - Late 1998 The first design with the new Ordnance Survey logo. |  Late 1998 - Early 1999 The cover now carries the ‘Millennium Products’ accolade. |  Early - Mid 1999 The Ordnance Survey logo gains a ® symbol. |
 Mid 1999 - Mid 2000 The ‘Explorer’ name gains a ™ symbol. |  Mid 2000 The Ordnance Survey web address is rather crudely shoe-horned in! |  Mid 2000 - Mid 2001 The OS logo shrinks to make more room for the web address. |
 Mid 2001 - Mid 2003 The ‘Millennium Products’ logo is no longer used. |  Mid 2003 - Mid 2006 The website address is removed; the OS logo remains the same size. |  September 2004 onwards New-style cover. |
Page last updated: 24 April 2011