Inter alia , a computer program product for use on a processor for determining an elevation differential between a first location and a second location, wherein a fluid flow control device (200) is located at the first location, the fluid flow control device including at least one liquid volume (302) in valved communication with the second location via a distal end (208) of a fluid line (204), the computer program product comprising a computer usable medium having computer readable program code thereon, the computer readable program code characterized by: program code for reading and storing pressure values associated with the liquid volume program code for computing and identifying correlations between stored pressure values program code for calculating pressure values based on the identified correlations and program code for estimating the elevation differential based upon calculated pressures is disclosed.
