If the time on the plots or on the RAF photo title strips is prefixed by the
letter "Z" then it is "Zulu time", that is, local time on the ground. As
far as I know, all the RAF national survey photography (which includes this
1946 material you are looking at) was recorded at Zulu time.
You may be interested to read about the device invented by staff at the
Central Interpretation Unit (RAF Medmenham) during WWII to achieve exactly
the measurements you are trying to make. A brief description can be found
in Evidence in Camera by Constance Babington-Smith (1958, Chatto and
National Monuments Record Centre
T: 01793 414833
F: 01793 414606
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>I am trying to calculate the heights of objects shown in vertical aerial
>photographs from the length of their shadows. This is in connection with
>structures built in WWII and now demolished.
>The query that I have is this. To get a reliable angle of elevation and
>azimuth for the sun, I need to know the time that the RAF photographs were
>taken. The date was 7/7/46, but the time given on the AP plot is 0910. Is
>this GMT or Local time? Was/is there a convention?
>Any help would be much appreciated!