The Display of Symbols

The third page of the code prefix property sheet is called Symbol and an example of this is shown further on.  The fields in the page allow you to define how any symbols that are required for a feature using the current code prefix are to be displayed.  The Enabled check button allows you to specify whether a symbol will be displayed or not.  If it is ticked, a symbol will be displayed using the parameters in the dialog.  If not, the items in the property page will be disabled.

The Layer and Pen fields define the graphical attributes that n4ce will use.  The pen will only have an effect if the symbol was created with all the elements assuming the colour applied to the symbol.  This is the same as assigning the colour to BYBLOCK in AutoCAD

The Name field defines the symbol that will be displayed, and a preview of the symbol is given in the window beneath it.  The list in this field will vary with the number of points that are required by the type of feature symbol.  For instance, if a feature symbol requires two points, only those project symbols that have an origin and at least one handle will be listed.  This name can be overridden on any survey point by using the dimension SYM= with the name of the required symbol as the dimension value.  For example, when surveying trees, you may have different symbols for different species and you could set up a choice list of tree names for in-field use.  Further, you can define the dimension SYM=NONE such that no symbol is plotted.    

There are ten different ways in which points can be used to display a feature symbol in plan.  The Type field defines which display method is to be used.  There is an eleventh option in the list called Section Symbol which is only used when plotting detail on sections and, if selected, nothing will be displayed in plan.  

Scaling and Rotating Symbols 

There are two dimensions that are associated with certain types of symbol.  The Scale dimension, normally S, can be used to define the size of symbols and the Angle dimension, normally A, can used to define a rotation of symbols.  The angle expected is the polar angle where the positive x-axis is zero and anti-clockwise is positive.  If either of these dimensions is expected and not present, n4ce will look at the fields defined for the current code prefix for a default value.  If no default is present, a scale of 1.0 and an angle of 0.0 will be assumed.  If you wish to scale the symbol, you should create it at unit size.  If you wish to angle the symbol, you should create it horizontally so that the correct orientation can be applied.

The Retain Scale and Retain Angle check buttons can be used to remember the scale or angle dimensions that are used for displaying the symbol.  If these buttons are ticked, the value previously used in a string of symbols will be remembered for each symbol until a new dimension value is assigned.  They are only remembered for the current string of symbols so if a new feature string is started, the scale and angle values will be reset.

Symbols Using One Point

There are five types of symbol display that only require the use of one point.  The symbol could be displayed at every point that makes up the feature.  Each symbol will be displayed by matching the origin of the symbol to the feature point.

1 Pt Scaled          This option can create a symbol that can be scaled and rotated about the point.  To do this, the scale dimension defines the scale and the angle dimension defines the rotation of the symbol.

1 Pt Aligned         This option creates a symbol that is rotated using the direction of the feature at the point.  The symbol can be scaled using the scale dimension.  If the angle dimension is present, the dimension value will be added to the direction of the feature at that point.

1 Pt Request       This option is like the previous option except that an aligned symbol is only created when requested.  If you wish to plot a symbol at a point, the Request Symbol comma code, usually S, should be used.  The symbol can be scaled using the scale dimension and, if the angle dimension is present, its value will be added to the direction of the feature at that point.

1 Pt Ends              This is again like the aligned symbol option except that in this case, symbols are only plotted on the first and last points of the feature.  In the example to the right, the end points have also had the no marker comma code applied to them.  The symbol can be scaled using the scale dimension.  If the angle dimension is present, the dimension value will be added to the direction of the feature at its end.  Also, if the feature under consideration is a closed line feature, no symbol is plotted.

1 Pt Fixed             This option is used to display symbols that should always be displayed the same size, no matter what the working scale.  This type of symbol is often used for boreholes.  The symbol should be created at the size you want it displayed at a scale of 1:1000.  Therefore, if a symbol is to be plotted 2mm across, you should draw it 2m across.  The scale dimension has no effect on this type of symbols but if the angle dimension is present, the symbol is orientated accordingly.

1 Pt Scaled	1 Pt Aligned	1 Pt Request	1 Pt Ends

Multiple Point Symbols

There are five types of symbol display that require the use of two or more points which give the symbol an origin and a direction.  When the necessary symbols are created, you must define one or more additional symbol handles in addition to the symbol origin.  For a 2-point symbol, you must provide at least one handle and for a 3-point symbol, you must provide at least two.  The origin of the symbol will always be made coincident with the first point of those to be used.  The symbol will be aligned so that the direction between the symbol handle and its first origin will be the same as the direction between the first two points.  When creating the symbols, you should create them so that the line between the symbol origin and the first symbol handle is horizontal.

Each of the options calculates a scale factor in the direction of the first two points, Sx, and a scale factor perpendicular to that direction, Sy.  There are situations where either of the scales may be taken from the symbol scale dimension and these will be described where appropriate. The symbol angle dimension is not used for multiple point symbols.

2 Pt Aligned         This option is a simple aligning option where the symbol is aligned such that the direction between the symbol origin and the first symbol handle is the same as that between the two points used to construct the symbol.  If you define a symbol scale dimension, this scale will be used for both Sx and Sy.

2 Pt Stretched     This option allows you to stretch a symbol between two points by making the second point coincident with the first symbol handle.  The Sx value is calculated as the distance between the two points divided by the distance between the symbol origin and the first symbol handle.  No scaling takes place perpendicular to the direction of the two points and so Sy is set to 1.0.

2 Pt Scaled          This option allows you to scale a symbol between two points by making the second point coincident with the first symbol handle.  Again, the Sx value is calculated as the distance between the two points divided by the distance between the symbol origin and the first symbol handle.  The Sy value that is used is the same as the Sx value.

2 Pt Width             This option allows you to stretch a symbol between two points by making the second point coincident with the first symbol handle.  Again, the Sx value is calculated as the distance between the two points divided by the distance between the symbol origin and the first symbol handle.  The Sy value is taken from the symbol scale dimension.   For this option, it is assumed that you have created a symbol that is 1 metre wide.

3 Pt Symbol         This option allows you to stretch a symbol between two points by making the second point coincident with the first symbol handle and then use a third point to define a width.  The Sx value is calculated as the distance between the first and second points divided by the distance between the symbol origin and the first symbol handle.  The Sy value is calculated as the perpendicular offset of the third point from a line joining the first and second divided by the perpendicular offset of the second symbol handle from a line joining the symbol origin and the first symbol handle.

2 Pt Aligned	2 Pt Stretched	2 Pt Scaled
2 Pt Width	3 Pt Symbol	Continuous

The Continuous check button is enabled when you have selected the symbol type to be one of the first four options described above.  The normal operation of a 2-point symbol is that points are taken in pairs.  Symbols will be created using points 1 and 2, 3 and 4, 5 and 6 and so on.  If this check button is ticked, symbols will be created using points 1 and 2, 2 and 3, 3 and 4 and so on.  The example shows how the use of the gate symbol can be applied to a feature using continuous 2-point scaled symbols.  If the Continuous check button is ticked, n4ce will also look to see if the Polygon comma code, normally P, has been applied to either the first or last point in the current feature string.  If it has been applied, n4ce will create a 2-point symbol joining the last point on the feature string back to the first.

The Hide Second Points check button is also enabled for all multi-point symbols.  If this is ticked, only the first point used for each symbol will be displayed regardless of the point display settings.  Also, any text or annotation on the second or subsequent points will not be displayed.

The X&Y Scales is a new option introduced from 4.20c and above. It allows quick scaling of a symbol however it only works with 1pt Scaled, Aligned, Ends and 2pt Aligned.