Client implementation considerations

This page contains some general guidelines and suggestions for developers, who wish to implement their own software using HERE HDGNSS data.

IOD matching

Ephemeris data set is matched with the corresponding orbit and clock correction data set that has the same IOD value. When changes occur in any data type, it is not guaranteed that change in IOD will happen in a synchronized manner in all data types. This means that once ephemeris data, along with IOD, changes, orbit and clock corrections might still contain datasets with the old IOD. At this time, old corrections should not be used with new ephemeris data. Instead, old ephemeris data, along with corresponding orbit and clock corrections, should be used until a dataset with a new IOD value has been received from each datatype. It is the responsibility of the client software to implement, for example, a caching mechanism to ensure that IOD values of the ephemeris data and orbit and clock correction data match, when used together.

Galileo I/NAV and F/NAV

Galileo ephemerides provide different clock models for I/NAV and F/NAV. HERE HDGNSS service does not provide clock corrections for both. I/NAV clock model has been chosen to be the reference when deriving clock corrections. Hence, when using correction data provided by HERE HDGNSS service, one should use I/NAV ephemeris and clock correction data with all Galileo signals.

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