Options

See Apply a Network Adjustment Style.

General

Maximum iterations - Enter the highest number of computations allowed for the adjustment to meet the defined residual tolerance.

Perform Vertical Adjustment - Specify whether or not to compute delta elevations from total station observations.

Mean Angles - Specify whether the observations that make up mean angles are used individually or as a mean. This affects the way errors are estimated, but it has no effect on positions.

Variance Group

Customized network adjustment weighting - Enter the name for each custom variance group to which GNSS vectors can then be assigned for custom weighting in the least-squares network adjustment. This is in addition to the standard predefined variance groups already included in TBC, providing you with many easy-to-create weighting options customized to suit your needs.

Covariance Display

Express precision as – Select the method of expressing horizontal (2D) precision (P) as proportional errors. For horizontal precision, distance is the horizontal distance between points. Select one of these options:

• Ratio - Select this to express horizontal precision in units of one part in X (where X = distance ÷ P).
• PPM - Select this to express horizontal precision in units of X parts per million, where X = distance × P × 1.0e-06).
• None - Select this to disable the display of horizontal precision.

Propagated linear error (E) - Select the horizontal (two-dimensional) propagated linear error for the network adjustment style. The computed propagated linear error is at 1-sigma, regardless of the Univariate and Bivariate Sigma Scalars. Select one of these options:

• US - Select this option to use the standard error of adjusted horizontal (2D) or slope (3D) distance.
• Canadian - Select this option to use the largest semi-major axis of the 2D or 3D relative error ellipsoid.
• Bomford - Select this option to use the square root of the sum of the 2D or 3D relative error variances.
• Spherical - Select this option to use the mean of the 2D or 3D relative standard errors.

Constant term (C) - Type a value in current project units. The term must range from 0.0 m (0.0 US ft) to 0.1 m (0.3 US ft).

Express precision as - Select the method of expressing three-dimensional (3D) precision (P) as proportional errors. For three-dimensional precision, distance is the slope distance between points. Select one of these options:

• Ratio - Select this option to express horizontal precision in units of one part in X (where X = distance ÷ P).
• PPM - Select this option to express horizontal precision in units of X parts per million, where X = distance × P × 1.0e-06).
• None - Select this option to disable the display of horizontal precision.

Propagated linear error (E) - Select the three-dimensional propagated linear error for the network adjustment style. The computed propagated linear error is at 1-sigma, regardless of the values specified for the Univariate and Bivariate Sigma Scalars. Select one of these options:

• US - Select this to use the standard error of adjusted (horizontal (2D) or slope (3D)) error.
• Canadian - Select this to use the largest semi-major axis of the 2D or 3D relative error ellipse.
• Bomford - Select this to use the square root of the sum of the 2D or 3D relative error variances.
• Spherical - Select this to use the mean of the 2D or 3D relative standard errors.

Constant term (C) - Enter a value in current project units. The term must range between 0.0m (0.0 US ft) to 0.1m (0.3 US ft).

Scalar on linear error (S) - This displays the factor used to scale precisions to the desired level of confidence. For scaling relative covariance matrices, the propagated linear error is squared.

Covariance display for horizontal scalars

For the US, Bomford, and Spherical methods, these options are available:

• 1.000 1-sigma
• 1.969 (95%)
• 2.575 (99%)

For the Canadian method, these options are available:

• 1.000 (39%)
• 2.447 (95%)
• 3.035 (99%)

Covariance display for 3D scalars

For the US, Bomford, and Spherical methods, these options are available:

• 1.000 1-sigma
• 1.969 (95%)
• 2.575 (99%)

For the Canadian method, these options are available:

• 1.00 (20%)
• 2.80 (95%)
• 3.37 (99%)

Note: Set the precision confidence level in the Confidence Level Display section of the Computational Settings.

Restrict to observed lines

• Yes - Select this to limit the display of covariant terms.

  When this is selected, there is no effect on final adjustment results, except for preventing the display of covariant terms between points not connected by observations.

• No - Select this to compute covariant terms between every possible permutation of point pairs in the network.

For large networks, the list of covariant terms in the Network Adjustment Report could become very long.

Transformations

Compute latitude and longitude deflections - Select Yes to use latitude and longitude deflections to transform GNSS vectors to the local datum.

Compute azimuth rotation - Select Yes to use the azimuth rotation to transform GNSS vectors.

Compute scale factor - Select Yes to use the scale factor to transform GNSS vectors to the local datum.

Compute azimuth rotation - Select Yes to use the azimuth rotation to transform azimuths to the local datum.

Although typically you would not want to compute azimuth rotation, you might want to do so if, for example, you have control distributed around your network (but not at each end of a particular station-backsight line) and you do not want to hold one line as a reference bearing. In this case, the software will calculate one rotation to make the network best fit the distributed control.

Horizontal scale factor - Type a value for the factor to apply to horizontal distances from terrestrial measurements.

Although typically you would not want to apply a horizontal scale factor (other than 1), you might want to do so if you are working with survey data collected with older equipment.