Assuming that the milestone is actually included in the national database, you should be able to locate the milestone by using the place name based search facility in Google Earth.
However, you need to decide firstly which regional file to look in. This is not always obvious as we have based the regions of England on the pre-1974 counties classification. In some cases there were major realignments of county boundaries in the 1974 revision, one of the most well known being the district of Saddleworth near Oldham moving from Yorkshire to Lancashire.
If the milestone you are looking for is close to a regional boundary then it would be better to load all the neighbouring regional files. Once you have found the milestone, the 2 letter prefix of its National ID will tell you which old county and hence region it belongs to.
There are two possible contributory factors here - the OS grid reference is inaccurate, i.e. wrongly measured or recorded, or not precise enough, i.e. the number of significant figures provided in the grid reference is insufficient.
Many of the current milestone grid references in the National database were produced many years ago when the only method was direct measurement on Ordnance Survey maps. These early surveys adopted 3 figure references as this was the maximum precision that could be achieved by direct measurement.The majority of the 3 figure grid references provided are correct as far as they go in terms of significant figures. However, they are not very precise because 3 figure references only give positioning within a 100 metre square
Conversely,there are many instances of inaccurate grid references as the result of a wrong reading or transcription error that to date have been difficult to pick up until the Google Earth mapping presentation.
Today, there are tools such as SatNavs and other GPS position devices that can provide much more precise references and we are now standardising on 4 figure grid references as a result.
Some members have reported problems with seeing duplicate or even triplicate markers in Google Earth. These problems arise because Google Earth has the facility to store map files which are then displayed automatically each time Google Earth is loaded.
Sometimes you can save a file inadvertently when closing Google Earth or the program can crash unexpectedly, resulting in the currently loaded file being saved. In such circumstances, if you load the file for viewing as normal you will end up with 2 copies of the file being displayed.
Google Earth has two separate folders for storing map files:
Temporary Places used to hold any files you load just for the session
My Places permanent storage: files in the folder are displayed automatically
These folders are displayed in the middle section of the control panel on the left hand side of the screen called 'Places'.
When you load a map file, it is placed in the "Temporary Places" folder. When you close Google Earth, you receive the following message:
You have unsaved items in your "Temporary Places" folder. Would you like to save them to Your "My Places" folder?
Save Discard Cancel
If you select Yes, then any files you have loaded in the session are saved in the My Places folder. If you select No then the contents of the Temporary Places folder are deleted.
If you are seeing duplicate markers then you will find that both the My Places and Temporary Places folders have copies of the same file.
There are 3 solutions to the problem:
1 Do not load the relevant file anymore - just load Google Earth and the file will appear automatically
2 Switch off the display of the file in the My Places folder. This is done by removing the tick from the rectangular box before the file name under the folder name
3 Delete the file in the My Places folder and then load the file every time and ensure that you select Discard when you terminate the session. To delete the file, right click on the file name below the My Places folder name and then select Delete.
Option 1 is probably the simplest but will present problems when you want to view other files. Option 2 caters for viewing other files but is more complicated. Option 3 is probably the best compromise. With this option, don't use the Google Earth permanent storage facility at all. Just load and discard files every time.
Repository information has now been frozen and no further updates are planned. However, the society's master database spreadsheets will continue to be updated. Therefore, if you have discovered a new feature or that some of our information is incorrect, you can still tell us about it via the Report a Change menu option.
Our Repository information is being replicated on www.geograph.org.uk and new photographs with location details and grid references can be submitted as further development via the Submit a Photograph menu option.