In this contribution, we analyze how cosmic magnification may be detected in upcoming large photometric galaxy surveys. This effect arises as an enhancement or decrease of galaxy/quasar number counts at very high redshifts due to the magnifying weak lensing effect of intervening matter in the line of sight. It shows up in observations as a correlation or anti-correlation with low redshift galaxies. The size of this correlation is directly related to the galaxy bias and cosmological parameters. We focus on two particular cases: the Dark Energy Survey (DES) that will cover 5000 square degrees and reach i_AB<24 making measurements up to z~1.4 with a photo-z resolution of 0.05(1+z); the Physics of the Accelerating Universe Survey (PAU) at the William Herschel Telescope, which will initially cover 200 square degrees and reach the same depth with a much higher photo-z resolution of 0.0035(1+z). For this, we employ the simulations specifically prepared for both of the surveys and study the most important error contributions in each of the cases.