Adjustment functionality in Integrity Monitor

The adjustment functionality is most important in a deformation analysis environment. Use it to perform a least squares adjustment of your angles (with terrestrial applications) and distances and/or of your network of processed baselines. The purpose of the adjustment is to:

• detect blunders and large errors,
• generate information for analysis, including estimates of precision values (D Northing, D Easting, D Height, D 2D, and D 3D), as well as the respective 3-s values),
• minimize corrections made to the measurements.

After a least squares adjustment is successfully performed, you can determine that:

• there are no blunders and systematic errors in the observations,
• any remaining errors are small, random, and properly distributed.

A least squares adjustment ensures good positional closures and estimates of repeatability; thus, it ensures the reliability of your current and future measurements.

Tip - The position adjustment functionality needs at least two terrestrial points or one station fixed. If not enough fixed points or fixed stations are available, a notification will appear in the Status Messages view. A possible reason is that not all fixed points are contained in the round measurement or only angles without distances have been measured. Another possible reason is that all fixed stations are disconnected (for example, because of data outages).
A further notification appears, when the adjustment restarts delivering results.

To complete a successful adjustment with GNSS data, a least squares network must meet these criteria:

• The network must close geometrically and mathematically.
• The sum of the weighted squares of the residuals must be minimized.

Results of the adjustment are the following:

• Conversion of raw terrestrial measurements (horizontal and vertical angle, EDM slope distance) or baseline vectors to a set of position coordinates,
• With a Terrestrial Engine PP: Establishment of points with coordinates in the global point list,
• Residuals moved to points and to stations which are not held fixed.

Note for the Terrestrial Engine PP - For each point, the Integrity Monitor creates an entry in the point information list. Points are identified by their point name. Notwithstanding the number of imported files or rounds, exactly one entry is created for each point. The global point list only contains points for which an adjustment has been performed successfully at least once.

Adjustment type

The functionality is comparable to a fully constrained adjustment; once the network is bound to the fixed points / stations, adjusted coordinates for all other points and/or stations in the network can be determined.

Adjustment of Trimble 4D Control Server data using Trimble Business Center

In combination with the Trimble office software Trimble Business Center, Trimble 4D Control Server users have a wider selection of adjustment options.

• With a free adjustment (no station or point fixed), one can generate reliable error estimations and verify network consistency.
• For constrained adjustments in a Trimble 4D Control Server approach, one can determine scalars that allow the weighting of observations and measurements from different types of data sources.

For performing adjustments of Trimble 4D Control Server data in Trimble Business Center, use the Integrity Monitor export function that creates a *.vce TBC project file for the selected Integrity Monitor module. This project file contains the terrestrial measurements and /or GNSS observations provided by the parent module together with coordinate system information and can then be opened in Trimble Business Center.

Using weighting scalars

When performing an adjustment with observations and measurements derived from different types of data sources, one has to deal with the fact, that the variabilities (expressed in the standard deviation) of data types differ. In an approach that does not respect these differences, the adjustment may result in incorrect values. Introducing weighting scalars, however, allows optimizing the adjustment process and leads to a better error estimation.

The properties of the Integrity Monitor Weighting Scalars (sub-)category allow one to enter weighting scalars, which have been determined using the Trimble Business Center software (see above) to be applied for members of an observation or measurement group, such as, for example, slope distances or RTK vectors. Values between 0 and 1 will increase the importance of these observations, values higher than 1 will reduce their weight. A weighting scalar of 1 does, of course, not change the a priori standard deviation.