In the short‐arc algorithm used at AFGL, the data consist of altimeter observations. The smoothed surface approximating the geoid is described by a truncated set of spherical‐harmonic potential coefficients, and each satellite arc is described by six state vector components. Certain tidal effects are also included in the adjustment model. However, each tidal constituent considered is attributed to only two adjustable parameters: a global amplitude factor and a global phase angle correction. These parameters, representing very special linear combinations of spherical‐harmonic tidal coefficients, are essentially uncontaminated by geoidal errors or systematic orbital errors. Such an advantage would not exist if the adjustment were made in terms of the tidal coefficients themselves. Satellite altimetry adjustment with tidal parameters yields the geoidal residuals which can serve in a variety of tasks, such as studying ocean‐bottom phenomena, refining the geoidal resolution on a regional scale (which may include a more detailed description of tidal characteristics), or refining the global oceanic geoid.
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