Projecting Points

The Project option allows you to perform point projection options onto a line feature or other linear object.  For example, you may wish to project manholes onto road centre lines for chainage information or river dippings onto a nominated reference line.  When selected, the dialog box shown below is displayed. 

The Projection Object

• The Project To group allows you to define the object onto which projections are to take place.  There are five radio buttons giving you options as follows.
• Line Feature - This allows you to project points onto a line feature in the current model.  If you are moving the point to the projected position or copying the points at the projected position, the Burn check box will be enabled.  If checked, any projected points will be inserted into the reference feature and given the same code.  If not, copied points will be created without changing their code.
• Feature Segment - This allows you to project points onto a line feature segment in the current model.  Unlike the option above, you cannot burn your projected points into the line feature segment.
• CAD Polyline - This allows you to project points into a CAD polyline.  The polyline can be either in the dedicated CAD backcloth or one of the CAD models in the current backcloth.  Note that CAD polylines are assumed to be 2D.
• Design Sections - This allows you to project points onto a design line to calculate the chainage and offset of each point from the design line.  It assumes that the points of the model are in sections and looks for the seed point on the design line.  A design line has dimensions for chainage and bearing and may also include one for radius.
• Alignment - This allows you to project points onto an alignment design to calculate the chainage and offset of each point from the alignment.
• The From Backcloth check button allows you to specify that the reference feature you wish to project to is in the current backcloth.  Note that if this check button is checked, you cannot burn the created points into the reference feature
• You should note that if there is more than one possible result from the projection, the closest point is assumed.  The Maximum Distance check allows you to specify a maximum distance over which projections can take place.  Therefore, if the calculations produce a closest point that is further away than the maximum distance, no projection is performed.  This maximum distance is defined in the Max Distance field.  Note that this option is not available and the maximum distance has no effect on either the design sections or alignment options.
• Sometimes, the reference object, line feature or CAD polyline, to which you are projecting has only two points.  The Extend 2 Point check button allows you to project a point to this reference even if the new point is not between the two points.  This option is not available for the design sections or alignment options.  If you are projecting to a line feature segment, this option is assumed by default.

The Projected Points

• The Type drop list allows you to specify what to do with the projected point that is calculated.  There are three options as follows.
• Copy - A copy of the original point is made and moved to the location of the projected coordinates.  Any dimensions that are created will be added to the new point.  If the projection is to a line feature and the Burn check button is ticked, the new point will be inserted into the line feature and given the same code.  The Add to List check button also allows you to add the new points to the point list.
• Move - The original point is moved to the location of the projected coordinates and any calculated dimensions added to it.  If the projection is to a line feature and the Burn check is ticked, it will be inserted into the reference line feature and given the same code.
• Neither - The calculations are performed but neither a move nor a copy takes place.  Instead, the calculations will only be used to add the selected dimensions to the selected points.
• Half Distance - Works in the same way as Move, but moves the point half the distance.  The option is very useful when wanting to define a centerline between two features that are varying the distance between them.

The Height drop list allows you to specify how the heights of the projected points are to be calculated.  This will only be available when you are either moving or copying points and there are three options as follows.

• Interpolate - The height of the projected point will be linearly interpolated along the reference element.  If the reference element is 2D, then the height will also be 2D
• Retain - The height of the projected point will be the same as that of the original point.
• Null - The projected points are assumed to be 2D.

Maximum Distance: This is the distance that n4ce will look for a suitable projection.

Accept Closest Miss:  Allows you to accept the closest "miss" when projecting nearly parallel features!

The example below shows a feature before and after projection.  The two points in the top centre have been moved onto the reference feature.

Before Projection	After Projection

If you are using either of the option to project points to design sections or an alignment, the above dialog fields are disabled as only the calculations of the points in relation to the design line or alignment are carried out.

Projected Point Dimensions

When creating the projected points, n4ce can add up to nine possible dimensions.  These are as follows.

• CODE - This dimension is the code of the projected point and is added if the Point Code check button is ticked.
• OFFS - This dimension is the horizontal distance between the original and projected points and is added if the Offset Distance check button is ticked.
• SDST - This dimension is the slope distance between the original and projected points and is added if the Slope Distance check button is ticked.
• DZ - This dimension is the vertical height difference between the original and projected points and is added if the Height Difference check button is ticked.  If the value is positive, the projected point is above the original point.
• SLOPE - This dimension is the slope between the original and projected points expressed as 1 in n and is added if the Slope (1 in) check button is ticked.  If the value is positive, the projected point is the above the original point
• GRADE - This dimension is the grade between the original and projected points expressed as a percentage and is added if the Gradient (%) check button is ticked.  If the value is positive, the project point is above the original point.
• CHN - This dimension is the distance along the reference object and is added if the Chainage check button is ticked.  If the reference is a line feature and there is a chainage dimension on the first point of the reference feature, you will be asked if you wish to add this value to the calculated distances.
• BRG - This dimension is the bearing of the reference object at the location of the projected point and is added if the Bearing check button is ticked.
• PBRG - This dimension is the bearing of the projected point from the original point and is added if the Perpendicular Bearing check button is ticked.
• CANT - This dimension is the rail cant between the original and projected point and is added if the Rail Cant check button is ticked.  The calculation of this value assumes a rail width of 68mm.

Note that if you are projecting to a polyline, you can only create the horizontal offset and chainage dimensions.

Two further check control the values of some of the dimensions.  The Reverse Dimensions check button will reverse the direction of the slope or perpendicular bearing dimensions.  The MX Interface check button will cause a negative value of the perpendicular bearing if the slope is in fill.

Unable to Project Points

There are situations where points cannot be projected onto the reference object.  In the case of the Line Feature or CAD Polyline, the point could be outside the scope of the object.  When projecting using design sections, there may not be a compatible point on the design line.  The points will also not be projected if a projected point cannot be found within the maximum distance.

When in the element pick mode, if the indicated point cannot be projected onto the reference object, a simple message dialog will be displayed giving you the code and number of the point. 

When in either the rectangle or list pick mode and one or more of the points cannot be projected, a report window will display the codes and numbers of those points that cannot be projected.  You are also given the option to place these points in the select list for further examination.  Note that the list will be cleared before the failure points are added.