TPC associates a Least Squares Network with each survey. This network is created when you access the Least Squares Network Adjustment command. TPC analyzes the survey to create the Least Squares network then stores the network data and solution in a file with the same filename as the survey and the extension .LSA (Least Squares Analysis).
What is a Least Squares Network?
A Least Squares network is not limited to the sequence of points defined by a traverse. Although Least Squares can use the points defined by a traverse, it can also combine traverses to form a network then solve the network simultaneously.
Solving a network allows you to reconcile all your data at once providing the strongest solution possible. Surveyors often talk about the ‘fit’ of a survey. How one control loop fits well with a preexisting control loop. Or how the survey ‘fits the grid’ because the ties to existing monuments are tight. A Least Squares network looks at this kind of ‘fit’ over the entire project and says, “Here is the best fit, given all the information.”
Creating a Least Squares Network
You create a Least Squares network from the TPC Desktop by choosing Tools | Least Squares Network Adjustment. TPC displays the Least Squares Network Adjustment dialog
If you have previously analyzed or adjusted, TPC loads the network data from your last session. You may need to Solve the network again to pick up where you left off, since TPC doesn’t store all the solution data.
Using Traverses in a Network Adjustment
Although traverses can be used to build the data in the network, the network is not comprised of traverses. Instead, it is comprised of individual coordinates and observations from the survey. A foresight in a traverse, for example, would add both the occupied point and foresight point to the network and the horizontal angle and distance as separate observations. In a 3D network, the vertical data would also be added to the network. The traverse closing point and closing angle are also included in the network.
TPC also looks for redundant observations in each traverse. This can be a distance and / or angle recorded to an existing control point that was not part of a traverse.
A Network Solution Requires At Least One Fixed Point
A Least Squares network solution requires at least one point to be fixed. If you have not fixed at least one point in your Least Squares network, TPC can not solve the network.
When TPC generates the Least Squares observations, you can tell it to fix any survey points that are protected.
Sample File
TPC includes the file Ghilani Example 16-2 Network.trv in the Sample Surveys.
Ghilani Example 16-2 Network (8:53) - Least Squares Network, Example 16-2 from adjustment computations, SPATICAL DATA ANALYSIS, 5th Edition, Ghilani 2010, Wiley & Sons
