A method for transmitting data from a downhole tool to a surface location includes running a downhole tool into a wellbore. The downhole tool includes a pressure sensor. An annulus pressure in the wellbore is measured at a first time, using the pressure sensor, to produce a first pressure measurement. The first pressure measurement is compressed to produce a reference sample. The reference sample is transmitted to the surface location. The annulus pressure in the wellbore is measured at a second time, using the pressure sensor, to produce a second pressure measurement. A difference between the first pressure measurement and the second pressure measurement is determined to produce a first delta pressure measurement. The first delta pressure measurement is compressed to produce a first compressed delta pressure measurement. The first compressed delta pressure measurement is transmitted to the surface location.