The Point Code field shows the code prefix that will be assigned to new points. The drop down contains all the code prefixes that have been defined in the current project. When a point is created, it will form part of a new feature. It is important to distinguish between the features so that you know when one starts. The String Numbers group defines what is added to the code prefix to make up a code as follows.
None - The code assigned to all features will be the selected code prefix. This is normally used when you are generating single point features such as spot levels or telegraph poles.
Numeric - A new string number will be added to each new feature string created. The current model will be searched to find the highest string number already used for the required prefix. Each new feature will then have a string number incremented from that start number
Use ,N - The code for each feature will be the prefix with a new feature comma code (,N) assigned to the first point on each feature.
The Start Point Number field is used to define the number of the first point that is created. As each point is assigned a number, this value will be incremented. The Prefix Created Points check box allows you to add a number prefix to each point and for point generation, this is a G.
The Maximum Spacing field defines a maximum length for new feature segments. If the distance between points exceeds this value, extra points will be created. If you wish to disable this function, set this value to 0.0.
The Layer is Code check box overrides the way in which the code is assigned to a point. If this check box is ticked, the code assigned is the name of the layer on which the CAD element is resident.
The Check Duplicates check box allows you to ensure that there are no duplicate points generated. This can happen when objects representing points are plotted at the vertexes of lines. Firstly, you would generate the points from the line objects. Secondly, you would generate points from the symbols with this check button checked. Where a point symbol is coincident with a line vertex, a point would not be created.
The Add Points to List check box allows you to automatically add all new points to the Select List of points.
The Filter Along Lines check box allows you to filter dense points from polylines such as curve-fitted contours. If this is checked, the Filter Offset field is enabled. The algorithm that is used is a recursive Douglas-Peucker simplification algorithm which looks at the offset of points from the linear. Starting with the line joining the first and last points of the polyline, the point with the maximum offset from that line is found. Assuming this maximum point has an offset greater than the defined value, the polyline is split into two new lines, from the start to the maximum point and from the maximum to the finish. These two lines are then treated individually in the same way. This process continues until the offsets of all the points between the start and finish points of each line are less than the filter offset value. If there are gaps in the polyline, the lines on either side of gaps are treated independently and the gaps honoured with a gap comma code. Any simplification of the polylines takes place before any maximum spacing is applied. For a full description of how this algorithm works, search for “Douglas-Peucker” in your internet search engine.
The Trace Lines check box will reduce the number of points that are created when you have exploded CAD elements. For example, if a contour polyline has been exploded to a series of single segment lines, you would generate about twice as many points as necessary. If this check box is ticked, duplicate end points will be removed and longer feature strings created. In some instances, degradation of the data can take place meaning end points are no longer exactly coincident. You can elect to apply a tolerance to the search process by checking the Trace Tolerance check box. The Trace Tolerance field then allows you to specify this value.