STAGE 1 IS TO BE SOLVED AT HOME, STAGE 2 IN THE FIELD
Stage 1
This is a photograph of a Consolidated B-24 Liberator. But what is behind the picture? (CSI)
The Consolidated B-24 Liberator is an American heavy bomber, designed by Consolidated Aircraft of San Diego, California. The B-24 was used extensively in World War II. It served in every branch of the American armed forces as well as several Allied air forces and navies. It saw use in every theater of operations. Along with the B-17, the B-24 was the mainstay of the US strategic bombing campaign in the Western European theater.
N52 24. [Andrews Field (Great Saling)] [Attlebridge] [Alconbury]
E001 19.[Bassingbourn] [Bottisham] [Birch]

This will take you to an important location. At this place you will be able to discover the co-ordinates for the physical cache a short walk away (Stage 2, below).
Geochecker for Stage 1
You can check your answers for this puzzle on GeoChecker.com.
Stage 2 - Physical Cache
No 1, Serial No = AB - CDEFG
N52 24.B (C+D) (B+D) E001 19.(G-D) B (E/G)
***PLEASE TAKE NOTE OF THE TERRAIN RATING AT GZ. YOUR FEET WILL ALWAYS BE ON THE GROUND, BUT IT IS A DIFFICULT APPROACH. ATTEMPT AT YOUR OWN RISK.***