# GNSS surveys

In a GNSS survey, the controller is connected to the rover or base GNSS receiver. For a list of the GNSS receivers that can be connected, see Supported equipment.

The steps for completing measurements using a GNSS receiver are:

1. Configure the survey style.
2. If you are setting up your own base station, set up your survey equipment at the base and start the base survey.
3. Set up the rover receiver equipment.
4. Start the rover survey.
5. If you need to convert Global coordinates into local grid coordinates (NEE), perform a site calibration.
6. Measure or stake out points.
7. End the survey.

GNSS survey styles

All surveys in Trimble Access are controlled by a survey style. Survey styles define the parameters for configuring and communicating with your equipment, and for measuring and staking points. This whole set of information is stored as a template and used each time you start a survey.

The type of GNSS survey you will use will depend on available equipment, field conditions, and the results required.

Trimble Access provides two GNSS survey styles by default: RTK and RTX(SV).

Default survey styles are created by Trimble Access when a new installation of the software is started, but only if there are no existing survey styles.

When you start the survey, the Trimble Access software checks the settings in the survey style to make sure they are appropriately configured for the equipment you are connected to. For example, if GLONASS is enabled in the survey style it checks if the connected GNSS receiver or antenna also supports GLONASS. If the Trimble Access software detects an incorrect setting, or if it detects that the settings in the survey style have not been checked, it prompts you to confirm or correct the settings. Any changed settings are saved to the survey style.

Real-Time Kinematic surveys

The default GNSS survey style is RTK (Real‑Time Kinematic). Real‑time kinematic surveys use a data link to send observations or corrections from the base station to the rover. The rover then calculates its position in real time. Select the required data link type in the Data link options screen when you configure the RTK survey style.

Network RTK surveys

A Network RTK survey is a special type of RTK survey that uses a network RTK system to broadcast corrections to the rover. Network RTK systems consist of a distributed network of reference stations communicating with a control center to calculate GNSS error corrections over a wide area. Real‑time correction data is transmitted by radio or cellular modem to the rover receiver within the network area. The system improves reliability and operating range by significantly reducing systematic errors in the reference station data. This lets you increase the distance at which the rover receiver can be located from the physical reference stations, while improving on‑the‑fly (OTF) initialization times.

Select the required Broadcast format in the Rover options screen when you configure the RTK survey style. Trimble Access supports broadcast formats from the following network RTK solutions:

- FKP (RTCM)
- VRS
- RTCM3Net

To store VRS vectors to the nearest Physical Base Station (PBS) in the VRS network, the VRS system must be configured to output the PBS information. If the VRS system does not output PBS data, VRS data must be stored as positions.

If you are using a radio in a VRS system, you must select a two‑way radio. You cannot use Trimble internal 450 MHz or 900 MHz radios.

RTX (SV) surveys

An RTX (SV) GNSS survey receives centimeter-level positioning information from the Trimble Centerpoint® RTX correction service via satellite.

If needed, you can edit the survey style to change the constellations you want to track.

Other GNSS survey types

To use one of the following survey types, you must create your own survey style:

- FastStatic – a postprocessed survey using occupations of up to 20 minutes to collect raw GNSS data. The data is postprocessed to achieve subcentimeter precisions.
- Postprocessed Kinematic – postprocessed kinematic surveys store raw stop‑and‑go and continuous observations. The data is postprocessed to achieve centimeter‑level precisions.
- Real‑Time Kinematic and Infill – allows you to continue a kinematic survey when radio contact with the base station is lost. The infill data must be postprocessed.
- Real‑Time Kinematic and Data Logging – records raw GNSS data during an RTK survey. The raw data can be postprocessed later, if required.
- Real‑Time Differential Survey – uses the differential corrections transmitted from a land‑based receiver or from SBAS or OmniSTAR satellites to achieve submeter positioning at the rover.