In the field of mobile and user of the mobile location determination, geo-fences are used to identify areas and regions of commercial, safety and convenience to user of the mobile computer device. The methods disclosed reduce the central processor unit cycles of the mobile computer device and thus the power drain caused by high numbers of calculations required to determine the location of the mobile computer device relative to one or more complex shaped geo-fences by minimising the number of positioning calculations that the mobile device needs to perform. For location updates required by the mobile computer device, the method applies data structures to a deconstructed geo-fence prior to distance calculations for use by a geo-fencing application running on the mobile computer device.