Why a Spherical Earth Model?
Another question that is sometimes raised is why we chose to use a spherical earth model over an elliptical model, and how much “error” this introduces in the gridding geolocation. Keeping in mind that the EASE-Grid is simply a geographic data storage and retrieval mechanism, the answer is that no error is introduced by this model choice. Representation of the gridded data as a fixed array of values is accomplished with a set of equations to map from geographic coordinates (latitude, longitude) to grid coordinates (column, row). In this sense, the location (column and row) of each grid “cell” can just be considered an entry in a look-up table, i.e. a place to store the data (brightness temperature, albedo, time stamp, etc.) for a specific, implicitly defined, geographic location. As long as the transformation back from grid coordinates (column,row) to geographic coordinates (latitude, longitude) is performed with the inverse transformation that uses the same Earth model, there is no er
