I am new to PostGIS, Spatial Reference Systems and projections and want to store lat/lng coordinates retrieved from Google Maps and Openstreetmap and its services like the Geocoder/Nominatim. I'm working with data in America and the main calculations are for nearest neighbors. Results will be plotted back on a web map (eg: via Google maps API or leaflet)
Question: What spatial reference system is Google map using? I figured out so far that its the WGS 84 datum with the Mercator projection in the geographic coordinate system. Should I store the location data as it is, or transform to US National Atlas Equal Area EPSG:2163?
Since I will be calculating distances and finding nearest neighbors, if I guess correctly that doing nearest neighbor search requires transforming the entire table to EPSG:2163, then will the solution be to store the data in both Mercator and EPGS:2163?