# GNSS point options

As part of configuring the survey style for a GNSS survey, you can configure the parameters for the points measured during the survey.

To configure these settings, tap and select Settings / Survey styles / <style name> / <point type>.

Auto point step size

Sets the increment size for automatic point numbering. The default is 1, but you can use larger step sizes and negative steps.

Quality control

You can store quality control information with each point measurement except compensated points. Options may include QC1, QC1 & QC2, and QC1 & QC3, depending on the type of survey. All values at 1 sigma level, except horizontal and vertical precision estimates which are shown at the configured confidence level, set in the Precision display field of the Units screen.

Quality control 1: SVs, DOP and Time

Number of satellites (minimum for the occupation, number at time of storage, and list of SVs used in the solution), Flag for Relative DOPs (or not, used for legacy firmware that produced RDOP when static), DOP (maximum for duration of occupation), DOP at time of point storage, RMS (legacy systems only, in millicycles, this is from instant before going static to show roving environment, not a converged static reading), Number of GPS positions used in the occupation (this is the number of epochs within precision tolerance observed), Horizontal standard deviation and Vertical standard deviation field are unused (set to null), Start GPS week (the GPS week when you hit Measure), Start GPS time in seconds (the GPS second of week when you hit Measure), End GPS Week (the GPS week the point was stored), End GPS time in seconds (the GPS second of week when the point was stored, Monitor Status (not used, will be null or not visible), RTCMAge (age of corrections used in RTK solution), Warnings (which warning messages were issued during the occupation or in effect when the point was stored).

Quality control 2: Variance/Covariance matrix of the RTK solution

Error scale (added trace of covariance matrix divided by PDOP, used to convert DOPs into precisions in legacy systems), VCV xx, VCV xy, VCV xz, VCV yy, VCV yz, VCV zz (these are all a‑posteriori variances from the stored epoch of the RTK solution), Unit Variance (standard error of unit weight, always set to 1.0 for HD‑GNSS, not available in some legacy systems). All values at 1‑sigma level.

Quality control 3: Error ellipse of RTK solution

This is in local tangent plane and is calculated directly from VCVs using standard textbook formulae. Sigma north (standard deviation in the north component), Sigma east (standard deviation in the east component, Sigma up (standard deviation in the Up or height component), Covariance east‑north (measure of the correlation between the east error and the north error), Semi major axis length of error ellipse in meters, Semi minor axis length of error ellipse in meters, Orientation from north of error ellipse, Unit variance of solution. All values at 1‑sigma level.

Auto-store point

Select the Auto store point check box to automatically store the point when the preset occupation time and precisions have been met.

This check box does not appear in the Rapid point measurement options because rapid points are always stored automatically.

Occupation time and number of measurements

The Occupation time and Number of measurements together define the time that the receiver is static while measuring a point. The criteria for both must be met before the point can be stored. The Occupation time defines the length of clock time for the occupation. The Number of measurements defines the number of valid sequential GNSS measurement epochs that meet the currently configured precision tolerance that must occur during the period of the occupation time. When the Occupation time and Number of measurements criteria have been met, Store is available. Alternatively, if Auto store point is enabled, the point is stored automatically.

For compensated points and observed control points measured during an RTK survey, the horizontal and vertical precisions must also be satisfied before the point can be stored.

If a point is stored manually when the precision tolerances are not met, the number of measurements that meet the precision criteria will be zero, and this is what will appear in the point record in Review job.

The requirement for sequential epochs that meet the precision criteria means the occupation counters will be reset if the precision goes outside the tolerances at any time during the occupation.

In an RTK survey, the RTK engine in the GNSS receiver converges on a solution during the occupation and it is this converged solution that is saved in the job file when the point is stored.

In a FastStatic survey, the default occupation times are satisfactory for most users. If you change an occupation time, choose a setting according to the number of satellites being tracked by that receiver.

Changing the occupation times directly affects the outcome of a FastStatic survey. Any changes should increase this time rather than decrease it. If you do not record enough data, the points may not be successfully postprocessed.

Precision

In an RTK survey, set the Auto tolerance switch to Yes to enable the software to calculate horizontal and vertical precision tolerances that meet the GNSS receiver's RTK specifications for the baseline length you are measuring. To enter your own precision settings at which point storage is acceptable, set the Auto tolerance switch to No and then enter the required Horizontal tolerance and Vertical tolerance.

If the receiver is an older receiver, the Store RTK initialized only check box is available. Select the Store RTK initialized only check box to store only Initialized RTK solutions that meet the precision tolerances. Uninitialized solutions that meet the precision tolerances cannot be stored. When Store RTK initialized only is not selected, both RTK Initialized and Uninitialized solutions that meet the precision tolerances can be stored.

Auto-measure

If you are using a GNSS receiver that supports IMU tilt compensation or the GNSS eBubble, you can use Auto-measure to automatically initiate a measurement from within the Measure points screen.

Enable the Auto-measure check box in the survey style, or tap Options in the Measure points screen.

When using Auto-measure, the measurement will begin automatically:

- When using IMU tilt compensation and the IMU is aligned, and no movement is detected.

  The Status field shows Waiting to measure. You can tilt the pole as required, but make sure the pole tip is stationary. When no movement is detected, the status bar shows and the software automatically begins measuring the point.

- When using GNSS only, and the pole is within tilt tolerance.

  If the Status field shows Waiting for level, use the GNSS eBubble to level the receiver and make sure the pole is vertical and stationary. When the pole is within tilt tolerance, the status bar shows and the software automatically begins measuring the point.

Tilt functions

If you have selected the eBubble functions or Tilt functions check box in the Rover options screen of the survey style, select the Tilt warnings check box to display warning messages if the antenna tilts more than the threshold value entered in the Tilt tolerance field. You can specify a different Tilt tolerance value for each measurement type. See GNSS eBubble tilt warnings.

Auto abandon

To automatically abandon points when the position is compromised, such as where excess movement is detected during the measurement process, select the Auto abandon check box.

Store low latency positions

This check box only appears in the Continuous topo measurement method options when you do not have Trimble RTX or xFill enabled.

When you select the Store low latency positions check box, the measurements are made by the receiver in low latency mode. Low latency is more suitable when using continuous topo with distance based tolerances.

When Store low latency positions is not enabled, measurements from the receiver are synchronized on the epoch resulting in slightly more accurate positions, and is more suitable when using continuous topo with time‑based tolerances.

If using Continuous topo as a static test to check the quality of measured positions make sure Store low latency positions is not enabled.