The redshift is an observable quantity which is linked to both the distances that separate us from extragalactic sources and to the Universe’s cosmology. To constrain the nature of the dark universe (i.e., dark energy and dark matter) large cosmological surveys, such as the Euclid survey, require measuring redshifts for billions of galaxies. Such kind of mission must rely on photometric redshifts, which in return must have the best precision and accuracy possible. I this thesis, I worked on the validation and the improvements of the photometric redshift measurement methods planned for Euclid mission. I also explored novel methods to extract the photometry in large survey images, and to combine the data of different surveys in a configuration close to the expected Euclid one. Moreover, I investigated the possibility to use such kind of data to study the evolution of galaxies in dense environments.