Explore Georeferenced Maps - Help
This application allows a set of historical map overlays to be viewed. These are sets of maps that have had their sheet margins cropped to create a seamless georeferenced layer or mosaic. The application complements our Find by Place application that allows individual maps to be selected and viewed.
Watch a Help video on the Explore Georeferenced Maps viewer.
Main search process
1. Choose the historic map overlay that you would like to search from the left-hand list, and then use the gazetteer or map to zoom in to view the detail of the overlay.
2. Select the 2. Zoom to this historic overlay link to zoom to the selected overlay. This is particularly useful for the large-scale town plans, that only display at more detailed zoom levels. As you zoom or pan the main map, the historic overlay lists in the left-hand panel update to show just those that cover the current map view.
3. To take away the historic map overlay to display the background map/satellite layer, slide the transparency slider bar in the left-hand panel to the left. You can select different background layers using the drop-down list to the upper left of the map.
The following historic map mosaics are included in this application:
|Bartholomew - Ireland - Quarter Inch to the mile, 1940|
|British War Office - Ireland - One Inch to the mile, 1941-43 - (G.S.G.S. 4136)|
|Belgium / France|
|British First World War trench maps of Belgium/France, 1915-1918|
|British War Office (G.S.G.S.) Maps - 1:250,000 - 1:50,000, Belgium, 1942-1944|
|Ordnance Map of Hong Kong by Thomas Collinson, 1846|
|Maps of Jamaica by James Robertson, 1804|
Gazetteer, National Grid Reference, and Counties/Parishes for searching
The Gazetteer at the top of the map allows you to locate your area on the map using modern place names from Nominatim, as well as by British National Grid Reference - 2,4,6,or 10 figures. Further left, drop-down boxes allow counties and parishes (based on their names and boundaries in the 1940s) to be searched. In all cases, the map will then position to the place, National Grid Reference, county or parish that has been selected. We gratefully acknowledge the Vision of Britain project for allowing us to use these county and parish boundaries.
By default, the map shows modern Bing satellite imagery as a base layer, and the OS one-inch to the mile, 1885-1900 historic map overlay on top. Select one of the historic map overlay mosaics from the left-hand list to view a different historic map mosaic. Ordnance Survey Opendata, Bing Road and Hybrid base layers, MapBox streets or satellite layers, 1920s mapping from the NLS Historic Maps API, or OpenStreetMap mapping are also available as base map layers from the upper-right drop-down list. Google map and satellite layers are no longer available as the OpenLayers software we use does not support them, and also because the Google terms and conditions discourage the overlaying of other maps on top of Google layers. Double-click on the map, or SHIFT and drag with the mouse to zoom in on a rectangle, or click the zoom slider (upper left) to zoom in on the map. Hold the ALT and SHIFT keys down and drag with the mouse to rotate the view.
Zoom to this historic overlay
In order to make the location and context of the historic layers clearer, the historic map mosaics are displayed overlaid on a modern Bing satellite backdrop. If your selected layer is not visible, you may need to select the 2. Zoom to this historic overlay option.
Side by side viewer
The Side by side viewer allows all the different historic map overlays to be compared to each other, or to present day Bing, MapBox, OpenStreetMap or Ordnance Survey maps. The 'Side by Side' viewer is accessible directly from the Map Images home page as well as from the 'Side by side' link in the page header of both the Find by Place and Explore Georeferenced maps viewers. As you zoom or pan the 'side by side' maps, the historic overlays lists update dynamically to show just those relevant to the current map view. You can return to the standard 'Explore Georeferenced maps' or 'Find by Place' viewers by following the 'Explore Georeferenced Maps' link in the page header.
Hold the [Alt] and [Shift] keys, and drag with your cursor (ie. hold the left-hand mouse button down and drag) to rotate. Refresh the page or double-click the rotation arrow (top right) to return to the default rotation.
Screen Prints / capturing a screengrab
- By default, choosing the 'Print' option / Ctrl + P in most web browsers will result in the current map view extending across your default page for printing or saving what you can see on screen.
- If you alter your window aspect ratio by altering the height or width of your current browser window, then the map will fill different overall extents.
- In Firefox or Chrome you can Right-click on the map image and choose "Save Image As" to save just the current map view as an image.
Specific Map Sheet Reference
For our largest georeferenced layers, the map sheet you are viewing appears to the lower left at higher zoom levels
These tools allow you to trace a route to measure distance. Once selected, click the points on your route or area, and double-click with the mouse to stop the current measurement. Select the 'Return to normal mouse navigation' to cancel these measurement tools and use the mouse for normal selection, pan and zoom functions.
Linking to the viewer
The URL in your web browser address bar changes dynamically as you zoom and pan the map, and when you alter visible map layers and overlays. You may copy or bookmark the URL in your web browser address bar to save the current viewer location and zoom level.
In the lower-right of the map, the location of your mouse position is shown as a British National Grid Reference, as British National Grid Eastings and Northings, and as longitude and latitude, both in decimal and degrees, minutes and seconds forms.
To bring up the real-world location of your cursor as a pop-up so the details can be selected, hold the ALT key down and left-click with the mouse. This will bring up the British National Grid Reference, British National Grid Eastings and Northings, and longitude and latitude of the point you have clicked on.
The 3D viewer is accessible from the 3D tab in the footer of our Explore Georeferenced Maps viewer. You can alter your altitude, tilt and orientation to explore any one of our 600 georeferenced map layers draped over a 3D landscape. It is also possible to fade the transparency and view different base maps. The viewer uses Cesium for 3D geospatial visualisation, which is rendered via WebGL. WebGL is widely supported by modern web browsers - you can check if your browser is supported.
We have released the original OpenLayers 2 code behind this viewer on Github for onward use. We hope that other libraries, archives and institutions may benefit from the code in making available their geographical collections.
Please email firstname.lastname@example.org for further assistance, or to provide general comments/feedback.