The increase in the scale of traditional data sources, along with an explosion in the availability of sensor data, have originated massive volumes of data, a great deal of which is actually geolocated. This is partly due to the wide adoption of cheaper position technologies, and to the exponential growing of Volunteered Geographic Geographic Information (VGI) movements, which rely on crowdsourcing approaches. Big Data has generated a lot of interest amongst industry, the developer community and the public in general, and it has been at the core of many technology innovations which took place recently (e.g.: NoSQL, MapReduce); these new approaches already started to involve the geo community with projects such as the ESRI Spatial Framework for Hadoop or GeoTrellis, just to mention a few. However, the focus has been mostly on storing data (at the infrastructure level) and using data (at the analysis level), leaving aside challenges such as discoverability, integration or security. In this talk, we will address some of these outstanding challenges through the use of metadata and the semantic web, and show how the use of a decentralized and standardized catalog can help to unlock the five V's of Big Data: Volume, Velocity, Variety, Veracity, and most importantly, Value.