# PP initialization times

If you have set the Survey type field to PP Kinematic in the Rover options screen, the PPK initialization times item appears in the list of configuration screens in the survey style.

To define initialization times, tap PP initialization times.

To achieve centimeter‑level precisions from a PP kinematic survey when the data is processed, the survey must initialize. With dual‑frequency receivers, the on the fly initialization process begins automatically if at least five L1/L2 satellites are being observed.

In a postprocessed survey, only rely on the On the fly (automatic) initialization if you are certain that the receiver will observe at least 5 satellites without interruption for the next 15 minutes, or 6 satellites without interruption for the next 8 minutes. Otherwise, initialize on a known point.

During initialization, enough data is collected so that the postprocessing software can successfully process it. Recommended initialization times are:

Initialization method | 4 SVs | 5 SVs | 6+ SVs
--- | --- | --- | ---
L1/L2 on‑the‑fly initialization | N/A | 15 min | 8 min
L1/L2 new point intialization | 20 min | 15 min | 8 min
Known Point initialization | At least four epochs

- Generally the recommended times are appropriate. Reducing any of these times can affect the outcome of a postprocessed survey.
- You cannot initialize if the PDOP is greater than 20.
- The time to initialize counters are paused when the PDOP of the satellites being tracked exceeds the PDOP mask set in the survey style being used. The counters resume when the PDOP falls below the mask.

After initialization, the survey mode changes from Not initialized to Initialized. The mode remains Initialized if the receiver continuously tracks the minimum number of satellites. If the mode changes to Not initialized, you must reinitialize the survey.

On‑the‑fly initialization and new point initialization

If you do an On‑The‑Fly initialization in a postprocessed kinematic survey, you can measure points before initialization is gained. The Trimble Business Center software can process the data later to give a centimeter‑level solution. If you do this but lose lock on the satellites while initializing, remeasure any one of the points that you surveyed before lock was lost.

The number of satellites required depends on whether you are using satellites from only one constellation or a combination of constellations. After initialization, a position can be determined and the initialization can be maintained with one satellite less than the number required to initialize. If the number of satellites drops below this number, the survey must be reinitialized.

Satellite systems | Required satellites for initialization | Required satellites to produce positions
--- | --- | ---
GPS only | 5 GPS | 4 GPS
GPS + QZSS | 4 GPS + 1 QZSS | 3 GPS + 1 QZSS
GPS + GLONASS | 4 GPS + 2 GLONASS | 3 GPS + 2 GLONASS
GPS + BeiDou | 4 GPS + 2 BeiDou | 3 GPS + 2 BeiDou
GPS + Galileo | 4 GPS + 2 Galileo | 3 GPS + 2 Galileo
BeiDou only | 5 BeiDou | 4 BeiDou
BeiDou + GPS | 4 BeiDou + 2 GPS | 3 BeiDou + 2 GPS
BeiDou + GLONASS | 4 BeiDou + 2 GLONASS | 3 BeiDou + 2 GLONASS
GLONASS only | – | –
Galileo only | – | –

The QZSS system operates in the same time‑base as GPS and therefore is included in the counters as another GPS satellite.