You use ground forces - research geosurvey vehicles on the tech tree and then create a unit design using medium vehicles that has at least 1 geo survey component. Create a geo-survey formation and land it on the planet of interest. Once there they will automatically do the survey over time.
This is also how you do xenoarcheology, its exactly the same except you use vehicles with xenosurvey modules. Xenosurveys can sometimes take very long time.