# Manual – Isolines

Isolines connect points of constant scale or rotation They illustrate how scale and rotation locally change in the map. When generating the isolines, MapAnalyst computes a set of local geometrical transformations based on linked points. Not all pairs of points are considered for a local transformation, but only points that lie within a given radius around the transformation center. The set of local transformations is then used to extract the isolines.

## Local Scale and Local Rotation

Note that you can explore the value of each isoline by moving the mouse cursor over it. The local scale and rotation are displayed in the Toolbar in the

*Local Scale*and

*Local Rotation*text field at the top right of the window.

## Interface Structure

The left half of the control elements govern the computation and display of scale isolines, while the right half controls the rotation isolines.

## Show Isolines

The visibility of scale and the rotation isolines can be adjusted individually. Enable or disable the

*Scale*or

*Rotation*checkmark.

## Interval

Enter the equidistance between neighboring lines in the

*Interval*text fields. E.g., for scale isolines, a value of 5000 creates isolines at every scale change that is a multiple of 1:5000.

Symbolization

Adapt the color, width and type of the scale and rotation isolines for optimum readability.

## Radius of Influence

Enter the

*Radius of Influence*in the according field. The radius of influence controls the size of the radius around the local transformation centers (see above). A small radius of influence will generate isolines reflecting local variations, while a large radius of influence will generate isolines illustrating the global tendencies. It is recommended to try different values for the radius of influence until you find the most descriptive isolines. A good value to start with is approximately one third of the extension of the new reference map. The radius of influence is used for generating both the scale and rotation isolines.