# RTK initialization

The RTK initialization screen is not available with the Trimble DA2 receiver.

When you start an RTK survey, if base corrections are being received and there are sufficient satellites, the survey initializes automatically using the on the fly initialization method. A survey must be initialized before centimeter‑level surveying can begin. If initialization does not occur automatically, see To initialize on a known point.

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.

Initialization reliability depends on the initialization method used and whether multipath occurred during the initialization phase. Multipath occurs when GNSS signals are reflected off objects, such as the ground, a building, or trees. When initializing, always choose a site that has a clear view of the sky and is free of obstructions that could cause multipath. The initialization process in Trimble receivers is very reliable, but to reduce the effects of multipath, use good survey practice and periodically check your initialization by measuring previously measured points with a new initialization. To reduce the effects of multipath during an on-the-fly initialization, move around.

To reinitialize an RTK survey while roving

1. In the RTK Initialization screen select one of the following from the Method field:
   - Reset RTK

   - Reset SV tracking to drop all satellite tracking, reacquire satellites and reinitialize the RTK survey

     Resetting SV tracking in compromised GNSS environments is not recommended.

2. Tap Reset or Start.

To initialize RTK on independent subsets of satellites

You can initialize an RTK survey using independent subsets of tracked satellites. For more information, see To use independent subsets of satellites tracked in RTK surveys.

In the RTK Initialization screen:

- To initialize on the first independent subset of satellites, select Reset – track SV set A from the Method field and tap Reset.
- To initialize on the second independent subset of satellites, select Reset – track SV set B from the Method field and tap Reset.
- To initialize on all available satellites, select Reset – track all SVs from the Method field and tap Reset.

The Reset RTK and Reset SV tracking menu items operate on the currently selected SV tracking subset.

Required satellites for RTK initialization

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.

The minimum L1/L2 satellites required are:

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 | – | –

You cannot initialize if the PDOP is greater than 7.