Investigating Aerial Photographs

ROYAL AIR FORCE OPERATIONS IN THE MIDDLE EAST AND NORTH AFRICA, 1939-1943. (ME(RAF) 2402) Airmen photographers inspect developed reconnaissance film from a Type F.24 aerial camera outside a photographic trailer at a landing ground in Egypt. Copyright: © IWM. Original Source:

To follow on from my blogs covering the basics of researching Second World War defences in the UK, I’ve decided to cover the use 1940s Aerial Photographs to identify defences in your research/survey area.

I’m currently attempting to make sure these blog posts turn into a coherent guide that follows the process I use to research and record sites. I’ll try my very best not to get distracted or go off on a tangent along the way.

I intend to cover aerial photograph interpretation in a lot more detail when I eventually get around to writing a book (which will probably never happen!). So, I’ve decided to focus on a small sample of the more ephemeral defences you might encounter. This case study will also act as an introduction to these defences.

A Quick Disclaimer

As usual, I am not responsible for any issues that may arise as a result of using this case study.  I am currently very concerned about the issue of people trespassing on private property to access surviving sites. It is very likely that some of the sites presented in this blog sit on private property; so don’t trespass to view them! The landowner has a right to privacy and the right to not have their property violated or damaged. Trespassing has a knock-on effect on the survival of remaining sites and if people are trespassing to view defences ‘up close’, there’s the possibility that sites will be damaged as a result, or even demolished by the landowner.  Trespassing also hampers the work of individuals with a genuine interest in investigating, recording, interpreting and preserving the archaeological remains of 20th century defensive landscapes. Always gain express landowner consent BEFORE accessing a site. If your site sits within land accessible by public footpath don’t leave the footpath to take a closer look, unless you have the consent of the landowner. It’s also worth noting that private land does not need to be signposted; if you don’t see a sign it doesn’t give you the right to access. Always do your research, identify potential landowners and gain the relevant permissions in advance of any field work. In fact, it’s best to arrange to visit the landowner. This way you can explain why you would like to access their land, share your information, and discuss the site with the landowner. If you don’t get permission don’t access the land regardless.

Aerial Photographs

ROYAL AIR FORCE FERRY COMMAND, 1941-1943. (HU 93054) Vertical aerial view of RAF Hendon, Middlesex, soon after the completion of the new 1,159 yard secondary runway and extensions to the main runway. These overdue improvements were instituted following the transfer of Hendon from Fighter Command to Ferry Command on 1 April 1942, in order to handle the increasing aerial traffic and the larger aircraft employed. These included the Douglas Dakotas of N… Copyright: © IWM. Original Source:

Aerial photography is used extensively within archaeology to identify sites in a given area. Aerial photographs can reveal cropmarks and low lying earthworks which are frequently missed on the ground.

Aerial photography is also a key aspect in identifying forgotten or lost Second World War defence sites. 1940s aerial photographs of your chosen area may reveal unrecorded or lost defences, as well as defences that don’t often survive; such as trenches, barbed wire obstacles or roadblocks. Trenches and barbed wire were an integral and important part of the defensive landscape; identifying their location and presence will help you to build up a more in depth picture of the defences and defensive strategy.

Consulting aerial photographs as part of your Desk Based Assessment will allow you to highlight specific areas to focus on during your field work or initial walkover survey. The aim of your research should be to build up a picture of the defences in your area, using available documents and data. At this point you should already be building up a picture of the 1940s defences, and should already have a good idea of the range of defences that may survive and those that may have been destroyed.

Sources of aerial photographs

Google Earth Pro

I’ve mentioned Google Earth Pro in my previous blog. You’ll be pleased to find that 1940s aerial photographs for parts of the UK can be accessed via Google Earth Pro!

Simply press this button here-

Google Earth Historical Photography button

Sometimes you will need to slide the date slider back to 1940. Once you have done this, you’ll be instantly transported back to wartime Britain! It’s as simple as that! You can now start exploring your survey area, as long as you know what you’re looking for!

Please be aware that Google Earth doesn’t use the UK National Grid Reference system, so you’ll have to convert any grid references into coordinates, and vice-versa, using an app like the Grid Reference Finder.

Your local Historic Environment Record will use UK National Grid Reference system to record locations.

Historic England

As mentioned in a previous blog post, Historic England hold an archive of over 4 million aerial photographs; 95,000 of these can be viewed on the Britain From Above website.

Many of the 1940s aerial photographs are held within Historic England’s archives in Swindon. You can view prints free of charge in their Search Room.

For more information visit the Historic England website here

If travelling to Swindon isn’t possible, then you can request a free search of the aerial photograph archive; this will take around 15 days.

When requesting a search for your area it is useful to provide an accurate National Grid Reference for the centre of your site, depending on the size of your research/survey area.

This free search will provide you with a list of all the aerial photographs for your area.

Look for aerial photographs of your area dating from May 1940 and later. Aerial photographs from before May 1940 may not reveal Second World War defences, as construction didn’t commence until after the appointment of General Ironside as Commander-in-Chief of the Home Forces, on 27 May 1940; this date also marks the start of Operation Dynamo (The Dunkirk evacuation).

Once you have decided which aerial photographs you require, you can request copies. Photocopies are available, including enlargements of areas of interest.

Low and high resolution digital copies of the aerial photographs can also be purchased, but please be aware that these can be quite costly; however, they are invaluable when conducting a detailed examination of defence works.

You can find an up to date list of prices here.

Be aware that you will need permission from Historic England to reproduce the images or use them for anything other than personal study.

The Historic Environment Record/Sites and Monuments Record

Your local Historic Environment Record (HER) or Sites and Monuments Record (SMR) may also retain historical aerial photographs. This won’t be applicable to all HERs/SMRs, but it’s always best to make contact to check, and make them aware of your research/fieldwork. Your local HER should be able to provide valuable advice, or point you in the right direction. You can find the contact details for your local HER/SMR here

Site Types & How To Identify Them

THE BRITISH ARMY IN THE UNITED KINGDOM 1939-45 (H 3307) Pillbox camouflaged as a petrol station in Felixstowe, 24 August 1940. Copyright: © IWM. Original Source:

This brings us onto actually using aerial photographs to find Second World War defences. I’ve provided some examples that I’ve picked out of Google Earth using the 1940s aerial photographs from Kent and Cambridgeshire. Hopefully, this will help you to ‘get your eye in’.

Anti-Tank Pimples and Cubes

Anti-tank cubes and pimples were one of the most widely constructed forms of anti-tank defence. They could be found stretching for miles along the coast, as well as inland and were used to impede the movement of tanks and other vehicles across open ground.

THE POLISH ARMY IN BRITAIN, 1940-1947 (H 5493) Engineers of the 1st Rifle Brigade (1st Polish Corps) constructing beach defences at Tentsmuir in Scotland. The concrete blocks were used as anti-tank obstacles. Copyright: © IWM. Original Source:

The anti-tank cube, as the name suggests, was a large cube of reinforced concrete, often measuring between 1m-1.5m in width and approximately 1.5m in height. Many variations in height and width can be encountered. The cube was often reinforced with a single length of RSJ or railway track in the centre. They were cast in-situ using poured concrete and wooden shuttering (A wooden mould), but examples shuttered in brick and corrugated metal are known.

The anti-tank pimple on the other hand was smaller in comparison; looking like a flat-topped pyramid with a squared off base. These are around 90cm in width and 60cm in height and are frequently referred to as ‘Dragon’s teeth’.

Anti-tank cubes and pimples visible on the Isle of Grain in 1940

Anti-tank cubes and pimples show up very prominently on aerial photographs. They often appear as double lines of light coloured ‘blotches’ (see aerial photographs below), running in parallel.

Areas where they are commonly found include:

  • Long, exposed stretches of beach, especially around beach exits. Sometimes they are found at the base of cliffs; I believe this was done to prevent vehicles on the beach from seeking cover at the base of cliffs. The anti-tank cubes would ensure the vehicles stayed within the fields of fire of weapons employed to cover the beach.
  • Running parallel to roads to stop vehicles from leaving the road when attacked. This is often a sign of a prepared ambush and roadblock in the area.
  • Inland defences such as stop-lines and anti-tank island/defended locality/nodal point defences.

Anti-tank pimples adjacent Dover Castle


ANTI-INVASION DEFENCES IN BRITAIN DURING THE SECOND WORLD WAR (H 2465) Tank traps in a street in Farnham, Surrey. Copyright: © IWM. Original Source:

Roadblocks were employed to hamper the movement of tanks and other vehicles along the road network. Similar blocks were also employed on the rail network, as tanks can move just as well on the track bed as they can by road; these are known as ‘rail blocks’. There were several roadblock types employed during the war, two of which can be spotted on aerial photographs.

The first type of roadblock consisted of two large concrete blocks, similar to anti-tank cubes in appearance but substantially bigger, placed on each side of the road. The blocks also projected into the road, which significantly restricted the width of the road itself. The concrete blocks were slotted to accept RSJs (girders) or railway track which, when in place, ran across the road to block it.

THE HOME GUARD 1939-1945 (H 7330) The Home Guard: Home Guards erecting a road barrier during an exercise held in the north of Scotland. Copyright: © IWM. Original Source:

The second commonly encountered roadblock is the socket type. This involved cutting a series of holes into the road surface, into which RSJs or lengths of railway track were inserted. The holes in the road were fitted with a removable concrete cover. This ensured that car and bike tyres didn’t get damaged and also stopped people twisting their ankles in them during the blackout.

THE HOME GUARD 1939-45 (H 15191) Home Guard soldiers in York prepare a roadblock by inserting metal girders into pre-dug holes in the road, 2 November 1941. Copyright: © IWM. Original Source:

You may be relieved to find that these roadblocks can be spotted from the air.

The concrete blocks of the block type roadblocks look very much like anti-tank cubes from the air. You will see in the image below that they are substantially bigger and can be seen flanking the road in pairs. You may also spot them in gaps within lines of anti-tank cubes in areas where access was required or where they intersected a road.

Three block type road blocks covering a road in West Hythe

The socket type roadblock appears as a series of light patches in the road surface; these are often evenly spaced and stretch across the road. They will often be sited near to a pillbox or spigot mortar emplacement. Using the locations of defences you have gathered from the Defence of Britain records may help you pinpoint a roadblock and vice-versa.

Socket type roadblocks in Dover, 1940

Roadblocks can often be found:

  • Near to bridges crossing viable anti-tank obstacles suck as river and deep railway cutting.
  • Covering road intersections and crossroad.
  • Defending the road and rail approaches to villages, towns and cities.

Roadblocks seldom survive today, especially the socket type as they were removed in the post-war period or simply tarmacked over during road repair and improvement.


THE BRITISH ARMY IN THE UNITED KINGDOM 1939-45 (H 2702) A soldier of the 4th Battalion, The Royal Norfolk Regiment, mans a trench near a pillbox at Great Yarmouth, 31 July – 2 August 1940 Copyright: © IWM. Original Source:

Trenches are very much overlooked and underrated when it comes to defences of the Second World War. Trenches were highly important and actually afforded a greater degree of protection than pillboxes. Pillboxes would be accompanied by a supporting network of trenches; these would cover the pillbox’s blind-spots and provide a greater field of fire for the supporting infantry outside the pillbox.

Trenches come in many shapes and sizes, with the smallest ‘weapon slits’ accommodating two men through to more substantial earthworks capable of sheltering up to a platoon of soldiers (around 30 men).

Second World War trenches tend to be more sinuous and less extensive than their First World War predecessors, though you may spot angular or crenulated trenches dating from the Second World War. These crenulated/angular trenches generally consist of a single line of trench which lacks additional supporting trenches to the rear and the distinctive via zigzagging communication trenches, commonly found on First World War era trench systems, will also be absent.

Substantial semi-crenelated trench, Dover

It can be very difficult to tell the difference between a trench and existing field boundary. A trench will often have a visible mound to its front and rear; known as a ‘parapet’ (along the forward edge of the trench in the direction of fire) and ‘parados’ (along the rear of the trench). See the image below.

Beach defence fire trench, Birchington-on-sea

Freshly dug trenches are quite easy to spot as they will often have the lighter coloured spoil deposited to their front and rear (See first trench image and example below for comparison).

Sinuous trench with signs of spoil, Dover

Often, these trenches will be found apparently isolated in the landscape, and it’s always a good idea to check the top of cliffs and escarpments that sit to the rear of a beach. Another good place to look is within the forward edge of tree-lines and wooded areas.

Substantial trench system and pillbox following an established tree-line, atKingsdown.

Another interesting form of trench is the anti-glider trench. These earthworks were constructed to deny land that could be used by the enemy to land gliders. They often consist of linear ditches with a segmented earthen bank, and look something like this-

Anti-glider trenches at Great Stonar

Anti-tank ditches

THE BRITISH ARMY IN THE UNITED KINGDOM 1939-45 (H 2473) Anti-tank ditch near Farnham in Surrey, 24 July 1940 Copyright: © IWM. Original Source:

Anti-tank ditches, funnily enough, were ditches used to halt the movement of a tank. There were a number of different designs, which I may go into at a later date. Machine cut anti-tank ditches appear on aerial photographs as  long, straight sections of ditch with traverses set at regular intervals. These deliberate earthworks often cut through pre-existing features, such as field boundaries, and are highly visible. The traverses of the anti-tank ditch are often covered by a fixed defence such as a pillbox, anti-tank gun position, trench or spigot mortar position.

Machine cut anti-tank ditch, Great Shelford, Cambridgeshire

Many pre-existing earthwork, such as drainage ditches, were modified to act as anti-tank ditches. These can often be identified by redeposited spoil along their length as well as their proximity to other defences.

Anti-tank ditch using a modified existing earthwork and block type road blocks, Dover

Barbed Wire

INVASION DEFENCES IN THE UNITED KINGDOM (H 2187) Concertina wire defences along the sea front at Sandgate, near Folkestone in Kent, 10 July 1940. Copyright: © IWM. Original Source:

Barbed wire was deployed liberally throughout the landscape. Following the Dunkirk Evacuation, it was one of the few resources the Army had in abundance. Barbed wire entanglements, also known as concertina wire or Dannert wire, were sited to hamper the movement of attacking infantry and also used ensure infantry didn’t get within grenade throwing range of defensive positions. Barbed wire was often covered by withering fire from a flanking trench or machine gun position, otherwise the attacking infantry could walk right up to it and breach it without any trouble (which kind of defeats the whole point of an obstacle!).

Extensive barbed wire entanglements surrounding a military installation, St. Margaret’s Bay, Kent

Barbed wire defences are especially overlooked, very much like trenches, but play a vital role in the landscape of defence.

Barbed wire looks very different to hedgerows and field boundaries; it is a lot darker and semi-transparent in appearance. The images show some classic examples of barbed wire entanglements during the 1940s.

Barbed wire entanglement surrounding a defended locality, St. Margaret’s Bay, Kent

The End

So, that brings me to the end of this blog. Hopefully you will find it useful and not realise that I ran out of steam towards the end. As I mentioned at the beginning, I do hope to cover aerial photograph interpretation in a lot more detail in the future as part of a publication, if the opportunity arises.

Aerial photographs are a great resource that will help you discover the wider context of your chosen site.

Be sure to follow me on Twitter @ckolonko

Over and out.

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Investigating Aerial Photographs by Chris Kolonko is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
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One thought on “Investigating Aerial Photographs

  1. Pingback: Planning Your Project | Chris Kolonko

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