Estimation of reference barometric pressure by using dissimilar pressure references

A method comprising:

• receiving, by a data processing system, a first estimate of reference barometric pressure made by a first pressure reference network and corresponding to a first lateral location, wherein the first pressure reference network identifies the first estimate as corresponding to time t1, and wherein the first estimate of reference barometric pressure is based on i) the first lateral location and ii) a first measurement of barometric pressure made by a first pressure reference within the first pressure reference network;
• receiving, by the data processing system, a series of estimates of reference barometric pressure made by a second pressure reference network comprising a second pressure reference, wherein the series of estimates comprises:
• i) a second estimate of reference barometric pressure, wherein the second pressure reference network identifies the second estimate as corresponding to time t2, and wherein the second estimate of reference barometric pressure is based on a second measurement of barometric pressure made by the second pressure reference, and
• ii) a third estimate of reference barometric pressure, wherein the second pressure reference network identifies the third estimate as corresponding to time t3, and wherein the third estimate of reference barometric pressure is based on a third measurement of barometric pressure made by the second pressure reference,
• wherein the interval between time t2 and time t3 is less than the interval between i) time t1 and ii) the time at which the next estimate of reference barometric pressure is made by the first pressure reference network after time t1;
• receiving, by the data processing system, a fourth measurement of barometric pressure made by a first wireless terminal at time t4 while at the first lateral location;
• generating an enhanced estimate of reference barometric pressure based on:
• i) the first estimate of reference barometric pressure corresponding to the first lateral location, and
• ii) a difference in amount between the second estimate of reference barometric pressure and the third estimate of reference barometric pressure;
• and
• generating an estimate of the elevation of the first wireless terminal based on:
• i) the fourth measurement of barometric pressure made by the first wireless terminal, and
• ii) the enhanced estimate of reference barometric pressure.