Smooth strings
You can use this function to smooth contours produced by the CONTOUR EXTRACT function. The contours produced by CONTOUR EXTRACT are the most accurate representation based on the data from which the DTM was formed. However, these contours can be quite angular because they reflect the triangulated surface from which they are derived. You can use the SMOOTH STRINGS function to produce a more aesthetically pleasing representation of the data.
Prerequisites
The string file that you want to smooth is displayed in Graphics.
To run this function: Choose Edit > String > Smooth, or Surfaces > Contouring > Smooth strings in layer, or...
It is important to realise that using the smoothing technique generates new data points mathematically, and these may not exactly honour the original data. This can result in:
- crossed strings after smoothing
- data points on the wrong side of smoothed strings if both the smoothed strings and original data points are plotted together
Two smoothing techniques are available:
- cubic spline curve fitting to contour points
- simple cubic interpolation between points
For cubic spline curve fitting, you nominate how many sub-segments you want each contour line segment divided into. This results in an increase in data points by this factor. However, line segments less than 0.01 world data units long are discarded.
For simple cubic interpolation, all original points are retained and additional points are added between the existing points to create the curve of the contour. This means that the individual line segments will be smoothed but there may not be a smooth transition between line segments. This technique will only smooth segments with four or more points.
Whenever you use either of these smoothing techniques for presentation plots, you must check the resulting plot to make sure it is sufficiently accurate for your requirements.
Because of the increased number of data points in smoothed contours, plotting can take considerably longer.
String Range
The range of strings to be smoothed in the current active layer.
Segment Range
The range of segments to be smoothed in the current active layer.
Number of lines per segment
The number of line segments to be generated for each line segment in the original strings - a value between 2 and 10. The best value depends on you and the data, but remember the amount of data you have will expand by (up to) this factor.
Smoothing
Spline: The cubic spline curve technique is used to smooth the data.
Interpolation: The simple cubic interpolation technique is used to smooth the data.
Output
Graphics is updated with the smoothed range of strings and segments. Points are added to the string data file to produce the smoothing effect.