diff options
| -rw-r--r-- | location/java/android/location/GnssMeasurement.java | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/location/java/android/location/GnssMeasurement.java b/location/java/android/location/GnssMeasurement.java index 4cd3616566c2..ecdd4b616e0f 100644 --- a/location/java/android/location/GnssMeasurement.java +++ b/location/java/android/location/GnssMeasurement.java @@ -214,6 +214,25 @@ public final class GnssMeasurement implements Parcelable { * * <p> When this bit is unset, the {@link #getAccumulatedDeltaRangeMeters()} corresponds to the * carrier phase measurement plus an accumulated integer number of carrier half cycles. + * + * <p> For signals that have databits, the carrier phase tracking loops typically use a costas + * loop discriminator. This type of tracking loop introduces a half-cycle ambiguity that is + * resolved by searching through the received data for known patterns of databits (e.g. GPS uses + * the TLM word) which then determines the polarity of the incoming data and resolves the + * half-cycle ambiguity. + * + * <p>Before the half-cycle ambiguity has been resolved it is possible that the ADR_STATE_VALID + * flag is set: + * + * <ul> + * <li> In cases where ADR_STATE_HALF_CYCLE_REPORTED is not set, the + * ADR_STATE_HALF_CYCLE_RESOLVED flag will not be available. Here, a half wave length will be + * added to the returned accumulated delta range uncertainty to indicate the half cycle + * ambiguity. + * <li> In cases where ADR_STATE_HALF_CYCLE_REPORTED is set, half cycle ambiguity will be + * indicated via both the ADR_STATE_HALF_CYCLE_RESOLVED flag and as well a half wave length + * added to the returned accumulated delta range uncertainty. + * </ul> */ public static final int ADR_STATE_HALF_CYCLE_RESOLVED = (1<<3); @@ -1039,9 +1058,6 @@ public final class GnssMeasurement implements Parcelable { * with integer ambiguity resolution, to determine highly precise relative location between * receivers. * - * <p>This includes ensuring that all half-cycle ambiguities are resolved before this value is - * reported as {@link #ADR_STATE_VALID}. - * * <p>The alignment of the phase measurement will not be adjusted by the receiver so the * in-phase and quadrature phase components will have a quarter cycle offset as they do when * transmitted from the satellites. If the measurement is from a combination of the in-phase |