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Baseline

A baseline is a distance between two satellites that can be represented by its length and orientation or separated into two cartesian components or expressed in polar form. The term "temporal baseline" refers to the time interval between sucessive satellite observations.


Representations of baseline

At ASF, the baseline is separated into two components, which can change (linearly) across an image. These are:

  • Normal Baseline, the distance measured perpendicular to the center look direction.
  • Parallel Baseline, the distance measured parallel to the center look direction.
ASF's sign convention for the parallel baseline is opposite that of ESA. The sign conventions agree for the normal baseline.

The baseline is used to interpret satellite phase as elevation. During DEM generation, the baseline must be known very accurately (within a few centimeters). As the baseline is rarely known this well beforehand, it needs to be refined using a reference DEM.