To validate your coordinates first of all make sure that the latitude and longitude coordinates are not NULL in stores table, you can view it in WordPress Admin Panel Manage Stores.
If the coordinates are not null then make sure the coordinates (Lat/Lng) are in right range. Longitude is in the range -180 and +180 specifying coordinates west and east of the Prime Meridian, respectively. For reference, the Equator has a latitude of 0°, the North pole has a latitude of 90° north (written 90° N or +90°), and the South pole has a latitude of -90°. So maximum and minimum values are as follows.
The precision of location can be made accurate by the decimal places, so if your coordinates have five to six decimal places, the accuracy will be pretty high.