Understanding Network Adjustment
Use network adjustment to perform a least squares adjustment of your network of processed vectors. The purpose of the adjustment is to:
- Estimate and remove random errors
- Provide a single solution when there is redundant data
- Minimize corrections made to the observations
- Detect blunders and large errors
- Generate information for analysis, including estimates of precision
After a least squares adjustment is successfully performed, you can determine that:
- There are no blunders and systematic errors in the observations and control points.
- 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.
To complete a successful adjustment, 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.
The network adjustment process
All adjustment iterations are performed automatically when the process begins. Coordinates are shifted based on a fixed point, within tolerance levels that are set to limit the shift and end iterations. Once the residuals of the observations pass the criteria to end iterations, the adjustment stops (converges), and these functions are performed:
- The adjusted values for each point in the network are saved to the project as the current coordinate values, with qualities of Adjusted or Fixed in network adjustment.
- An additional coordinate is created for each adjusted point. The adjusted coordinate is promoted as the final value for the point.
- The adjusted values for each point appear in the Properties pane. You can analyze the results in the Run a Point Comparison Report.
