Level measurement is simple and complex. There are a number of considerations to take into account based upon you application. Gravity Measurement is discussed at length.
Several settings can be adjusted for the level measurement and reporting depending on the instrument model.
Dwell time between. Sets the amount of time the tracker waits after positioning the head before taking level samples. This gives time for the bubble level to stabilize before measurement.
Samples per measurement. The number of samples to average when measuring gravity.
Deviation Tolerance. Samples that exceed the specified tolerance (as a magnitude) are not included in the averaging operation.
Error Threshold.Leica trackers offer a single Error Threshold seting.
Monitoring level provides live readings from the level device. Monitoring level is useful for two primary reasons:
To ensure that the inclinometer is in range for a level measurement.
Monitoring changes in level to determine if a station move is needed.
While extremely accurate inclinometers typically need to be approximately level in order to operate properly. The instrument must be manually adjusted until the inclinometer is reading in-range
The Level Monitor displays 3 values:
TkrAz - Displays the current rotational angle of the trackers head in degrees. This value is typically counter clockwise from a standard starting location directly away from the home position.
LevelX - Displays the deviation in arc sections from vertical along the primary or X axis of the trackers level. This value is therefore a live reading along the X axis in the trackers current head rotation (TkrAz).
LevelY - Displays the deviation from vertical along the secondary or y axis of the trackers level, perpendicular the X axis if available (API trackers typically only have a single axis level built in).
The level values reported for the X or Y axis should not be trusted independently because any variation in the mounting of the level device relative to the trackers rotational center will influence the readings. Best practices should include verifying the readings after a full 180 degree rotation and the average of these two readings used in estimating the actual deviation.
Update Rate. Sets the rate at which updates are displayed in the interface.
Show X Decimal Places. Controls the number of decimal places displayed in the window.
Alarm. When enabled, the computer will beep and a message will be written to the log file when the specified angular tolerances are exceeded. The alarm will not sound when this window is closed.
Set Baseline. When clicked, the current values become the baseline or “reference” for establishing deltas for out-of-tolerance determination.
Display Level Values. The display is updated with raw level readings.
Display Deltas (Threshold). Shows angular deltas instead of absolute angular values. The threshold controls the limit that sets off the alarm.
When a gravity measurement is take within SA, this measurement is made relative to the instrument’s standing axis and is recorded as a Frame.
The Z-axis of this frame points upward along the gravity vector, and the XY plane of this frame defines the gravity plane. This frame measurement is saved directly on the instrument’s head such that the origin of the level frame is at the center of the instruments base frame and at the center of rotation for all angular point measurements.
Starting in 2025.1 each instrument station has an optional Vertical Alignment Check that can be enabled to display the alignment status of the station within the job file. For more details see the section on Instrument Straighten.
This mode is enabled automatically as part of a level measurement. When a Level Frame is Measured, the instrument's Level Frame is set accordingly, and the Vertical Alignment Check indicator is turned ON relative to it. The instrument level frame reference is listed in the instrument station's right-click menu:
Additionally, when OTG (Orient To Gravity, or Level Comp, or Virtual Level) is activated or deactivated, the Vertical Alignment check indicator is set accordingly. When OTG is is activated or deactivated, the instrument's Level Frame is set back to the Instrument Base.
More information on Gravity Measurements within SA can be found Here.