# To start the base survey

To set up and connect your surveying equipment when using a Trimble integrated GNSS receiver as a base:

1. Set up and connect the equipment at the base. See GNSS base receiver setup.

2. On the controller, start Trimble Access. If the Trimble Access software does not automatically connect to the receiver, see Auto‑connect settings.

If you are connecting a controller running Android to an SP60 receiver, turn off the Auto-connect to GNSS receivers function in Trimble Access, and always power up the receiver and wait until it is tracking satellites before attempting to connect the software to the receiver. If you attempt to connect to the SP60 receiver from the controller before the SP60 is ready then the Bluetooth pairing to the receiver can be lost.

3. Tap and select Measure and select the required survey style from the list.
4. From the Measure menu, tap Start base receiver.
   - If the controller is connected to a receiver that was logging data, the data logging stops.
   - If the base survey requires an internet connection and one doesn't already exist, the connection is established.

   - You can use a Custom radio if the radio you have is not listed.
   - When you start a survey, the Trimble Access software automatically negotiates the highest possible baud rate for communicating with the connected receiver.

   The Start base screen appears.

5. Configure settings for the base station:

   1. In the Point name field, enter the base station name and then enter the base coordinates.

      The Observation class field shows the observation class of the base point. For more information, see Storing points.

      If you carry out a real‑time survey using:

      - RTCM 2.x corrections and use a base point name that is more than eight characters long, the name will be shortened to eight characters when it is broadcast.
      - RTCM 3.0 corrections, you must use a base point name (in upper case) that is within the range RTCM0000 to RTCM4095.

   2. Enter values in the Code (optional) and Antenna height fields.

   3. Set the Measured to field as appropriate.

   4. In the Station index field, enter a value.

      This value is broadcast in the correction message, and must be in the range 0–31.

      Tap Scan to view a list of other base stations operating on the frequency you are using. The list shows the station index numbers of the other bases and the reliability of each. Choose a different station index number to those displayed.

   5. If the receiver you are using supports transmission delays, the Transmission delay field appears. Choose a value depending on how many base stations you intend to use. For more information about transmission delays, see Operating several base stations on one radio frequency

6. Tap Start.

   The base receiver starts to record data and transmit corrections in the format selected in the Survey Style.

   If you are carrying out a real‑time survey, a message confirms the base receiver has started.

   For a real‑time survey, check that the radio is working before leaving the equipment. The data light should be flashing.

   If you are logging data in the controller, and/or you are uploading corrections to a remote server, the Base screen appears. It shows which point is being surveyed and the time that has elapsed since data logging started. Leave the controller connected to the base receiver and set up the rover using another controller.

   If your base is operating as an internet server, the Base screen appears and in addition to the above, it shows the IP address that has been assigned to the base, as well as the number of rovers that are currently connected to the base.

   Disconnect the controller from the base receiver but do not turn off the receiver. You can now set up the rover receiver.