This ToggleValue turns automatic self-survey location determination on or off; when enabled the GNSS receiver computes its own position, and when disabled the position comes from the manually entered latitude, longitude, and altitude fields. Admins disable automatic survey and enter fixed coordinates when the antenna's exact surveyed location is already known and shouldn't be re-derived. For example, at a site with a precisely pre-surveyed antenna mount, the admin disables f3GPSReceiverPortSelfSurveyControl and enters the known coordinates directly instead.