Precise confluence location is determined using Global Positioning System receivers.
The number of 'primary' confluences is 41,253 (roughly 360 squared divided by pi) -- this is the same number of total square degrees on a sphere astronomers use to specify constellation areas. This number is obtained by filtering the 360 x 180 possible intersection points into 'primary' and 'secondary' confluences in such a way that there are not too many primary confluences near the poles.
Only confluences on land are included in the project. Since the ocean area of the Earth is 71%, this leaves roughly 12,000 points to be photographed. Many confluence points north and south of 49 degrees are arbitrarily declared unofficial. Nevertheless, volunteer explorers, especially in Europe, continue to add both official and unofficial confluence points.