We are preparing for a project where we'll need to survey a huge commercial building, room by room, floor by floor. We are planning to use Collector for ArcGIS. GPS function most likely will not work there, as the signal may not come through, and the sizes of areas to survey won't allow for accurate pinpointing anyway. Should we just abandon the geopositioning altogether, or perhaps there are other methods of locating the features using some permanent wifi stations, etc.?