To give a concrete example:
On day $1$, price of Gold $= 947.257$ GBP $= 1326.647$ USD and GBP-USD exchange rate = 1.40034
On day $2$, price of Gold $= 946.276$ GBP $= 1333.332$ USD and GBP-USD exchange rate $= 1.40903$
It can be seen that in GBP the price of Gold has decreased, whilst in USD the price has increased, which is obviously a function of the change in the exchange rate, but also perhaps indicative of a change in the "real value" of Gold.
Given this, I'd like to infer by how much the real, or intrinsic value of gold may have changed ( can be in percentage, logarithm or multiplicative factor ) without necessarily having to know the price levels of this value. Searching on this site I found this question, the answer to which, intuitively at least, seems to embody the type of approach I should take.