An active antenna apparatus with relative calibration for calibrating antenna elements , the active antenna apparatus comprising: antenna elements (1002, A11-A88) comprising a first antenna element (1002B, A44), a second antenna element (1002C, A45), and a third antenna element (1002D, A46), wherein the second antenna element (1002C, A45) is disposed substantially equidistant to the first antenna element (1002B, A44) and the third antenna element (1002D, A46) a probe (1004, PROBE1) disposed substantially equidistant to the first and second antenna elements (1002B, 1002C, A44, A45); and calibration circuitry configured to: identify a first relative relationship between the first antenna element (1002B, A44) and the second antenna element (1002C, A45) based on observations of one or more probe signals radiating between i. the probe (1004, PROBE1) and the first antenna element (1002B, A44), and ii. the probe (1004, PROBE1) and the second antenna element (1002C, A45); identify a second relative relationship between the first antenna element (1002B, A44) and the third antenna element (1002D, A46) using one or more antenna signals propagating between i. the second antenna element (1002C, A45) and the first antenna element (1002B, A44), and ii. the second antenna element (1002C, A45) and the third antenna element (1002D, A46); and determine calibration information for calibrating one or more of the antenna elements (1002, A11-A88) based on the first relative relationship and the second relative relationship. antenna elements (1002, A11-A88) comprising a first antenna element (1002B, A44), a second antenna element (1002C, A45), and a third antenna element (1002D, A46), wherein the second antenna element (1002C, A45) is disposed substantially equidistant to the first antenna element (1002B, A44) and the third antenna element (1002D, A46) a probe (1004, PROBE1) disposed substantially equidistant to the first and second antenna elements (1002B, 1002C, A44, A45); and calibration circuitry configured to: identify a first relative relationship between the first antenna element (1002B, A44) and the second antenna element (1002C, A45) based on observations of one or more probe signals radiating between i. the probe (1004, PROBE1) and the first antenna element (1002B, A44), and ii. the probe (1004, PROBE1) and the second antenna element (1002C, A45); identify a second relative relationship between the first antenna element (1002B, A44) and the third antenna element (1002D, A46) using one or more antenna signals propagating between i. the second antenna element (1002C, A45) and the first antenna element (1002B, A44), and ii. the second antenna element (1002C, A45) and the third antenna element (1002D, A46); and determine calibration information for calibrating one or more of the antenna elements (1002, A11-A88) based on the first relative relationship and the second relative relationship. identify a first relative relationship between the first antenna element (1002B, A44) and the second antenna element (1002C, A45) based on observations of one or more probe signals radiating between i. the probe (1004, PROBE1) and the first antenna element (1002B, A44), and ii. the probe (1004, PROBE1) and the second antenna element (1002C, A45); identify a second relative relationship between the first antenna element (1002B, A44) and the third antenna element (1002D, A46) using one or more antenna signals propagating between i. the second antenna element (1002C, A45) and the first antenna element (1002B, A44), and ii. the second antenna element (1002C, A45) and the third antenna element (1002D, A46); and determine calibration information for calibrating one or more of the antenna elements (1002, A11-A88) based on the first relative relationship and the second relative relationship. <EOS>