# Horizontal Line Fitting

TPC can find the best fit tangent line through a series of selected survey points. You may be able to tie a line of occupation, like a fence or a rock wall, but find it is is not exactly straight. Fitting a line to the points allows you to approximate the one line that best fits these points.

## Selected Points

In TPC, you fit a horizontal line to a series of survey points. These points can be consecutive points in a traverse, selected points in the Points Manager, selected points in a drawing or all the points in a traverse.

TPC uses the first and last selected points to compute the positions of the end points of the best fit line. So if point 200 is the first selected point and point 210 is the last, TPC will compute end points for the line that are as close to points 200 and 210 as possible. These will therefore be prependicular offsets to the end points of the best fit line.

## Types of Fitted Lines

TPC can compute three types of fitted horizontal (tangent) lines to a series of points.

### Least Squares

Uses least squares to compute the best fit line.

This is a minimally constrained solution, so the end point of the line can vary as needed to create the best fit. Once the line is computed, TPC computes the end points of the line so that they are as close a possible to the first and last selected points.

### Fixed Bearing

Compute the best fit line at a fixed bearing.

### Pass Through Point

Compute the best fit line that passes through an existing survey point.

This is a good option for a line that passes through a known corner.

## Typical Sequence

You will often fit a line as follows.

• Select the points you want to fit a line to in the Points Manager, Traverse Manager, a Traverse View or the Drawing View.
• Choose COGO | Fit Horizontal Line to display the Fit Horizontal Line Dialog.
• Select the Option you want and choose Compute.
• Choose the point labels you want for the computed points and choose Save and Plot to see the computed end points.

## Selecting Points

You can select points using the following methods.

### From the Traverse View

• Select the points you want to include in the best fit line. If you will be including all the points in the traverse, select just one point in the traverse.
• Choose COGO | Fit Horizontal Line to display the Fit Horizontal Line Dialog.

### From the Drawing View

TPC will set the What list to Entire Traverse: [traverse name] using the traverses that drew the object you right clicked.

### From the Points Manager

• Select the points you want to include in the best fit line. Remember that the first and last points selected determine the computed end points of the best fit line.
• Right click any selected point and choose COGO | Fit Horizontal Line to display the Fit Horizontal Line Dialog.

### From the Traverses Manager

• Select the traverse with the points you want to include in the best fit line. The entire traverse will be used for the computation.
• Right click the selected traverse and choose COGO | Fit Horizontal Line to display the Fit Horizontal Line Dialog.

TPC will set the What list to Entire Traverse: [traverse name] using the traverse you selected.