When creating parallel features, after the reference objects have been indicated, the Parallel Strings dialog will be displayed.
The Parameters group defines the basic data for the parallel feature. The String Code combo defines the code that will be applied to the new points. The defaults in the combo box drop list are the prefixes in the current code table. If the Default to Ref Code check box is ticked, the default for the code that will be displayed will be the code of the indicated reference feature. If not, the code will be code for the last parallel feature that was created.
If the Renumber Points check box is ticked, the Start Point Number field defines the start number for the newly created point numbers. If it is not checked, the point number is copied from the reference points. If the Prefix Created Points check box is ticked, a prefix of P will be applied to the number of the new points.
Where the reference feature turns through tight angles, it can happen that the parallel feature will cross itself and create cusps. If the Remove Cusps check box is ticked, n4ce will try and remove any cusps. If the Add to List check button is ticked, the created points will be added to the point list.
In its simplest form, the Offset field defines the horizontal offset that is used and the Parallel Offset field defines its value. If the Variable Offset button is checked, this field will be hidden and replaced by two fields, Start Offset and End Offset. In this case, the offset that is used at a given point will be linearly interpolated between the two offsets depending on the distance of the point along the reference feature.
The Heights section defines how the levels of the new points should be derived. The options are as follows...
Parallel Height Calculation
- Same Height: Will give the new points on the parallel feature the same height as that from the respective point on the reference feature.
- Constant Height: Will give the new points a fixed value. This will come from the Constant Height field which will be displayed when this radio button is set.
- Relative Height: Will give the points a height offset vertically from the respective point on the reference string. This will come from the Relative Height field which will be displayed when this radio button is set.
- Model Interpolation: Will give the points heights that are interpolated from either a DTM model or a referenced Point Cloud. In either case the target model or point cloud can be selected from the Reference model box. When interpolating onto a point cloud, options will be made available to choose the Highest, Lowest or Average point within a given search radius. If no point is located, the the point will be given a null level.
- Above Model: Will give the points heights a fixed offset above a selected model. The model is
selected from the Reference DTM combo box and the height offset will come from the
Relative Height field. Both fields will be displayed when this radio button is set. Note if a point cloud is selected, the same options are available as for the standard interpolation tool.
- Slope Value: Will give the points heights calculated from a gradient, taken from the Grade (1 in) field which will be displayed when this radio button is checked. If the slope is positive, the
new point will be calculated above the reference point. A relative height is calculated using
this slope and the parallel offset. For example, a slope of 1 in 1 with a parallel offset of 10m
creates a height offset of 10m up. The Slope Offset check box allows you to specify that
the parallel offset should be taken as a slope offset rather than a plan offset. If the
Percentage check button is checked, you can specify the slope by percentage gradient.
- Null height: Will give the points that are calculated no height at all.