Point Dimensions

Dimensions are used on points to give further information to n4ce about the object at a survey point.  For instance, if the point represents a tree, you can specify the spread of the tree canopy, the size of the tree bole and the height of the tree using dimensions.  The tree species could also be defined by a dimension. Dimensions are expected in the form of name=value where the name is the label assigned to the dimension and the value is a string representing the dimension.  Most dimensions are likely to be numerical although they can be alphanumerical as needed.  You can add as many dimensions as you wish to any point.

There are certain dimensions that are required in the given circumstances.  For instance, when displaying a tree at a point, a CAD symbol is typically used to show the canopy.  This CAD symbol will need to be scaled to represent the actual size so a scale dimension will be expected.  The Dimensions button from the code prefixes dialog allows you to define the names that n4ce should expect for these predefined dimensions.  When selected, the dialog box shown below will be displayed.

One of the pages on the main property sheet of the code prefix dialog is called Fields.  This can be used to set default values for dimensions so that you do not always have to assign dimensions in the field.  In some situations, if a dimension has not been assigned to a point and no default value is found, a value of 1.0 will be assumed.  When saving a code file for upload to a survey instrument, you should pay particular attention to this property page.  Any dimension defaults that are specified here will also be exported to the appropriate file and uploaded to the instrument.  When using the code whilst surveying, you will be asked to enter these dimensions.

Some of the dimensions in the dialog refer to a specific type of feature display and will be described in the appropriate section of this chapter.  Those that are not specific are described below.

Altering the Reduction of Survey Observations

When surveying, it is occasionally not possible to survey the exact point that is required.  For instance, when surveying posts and poles, you cannot survey the centre of the pole unless you climb the pole and place your target on the top.  Four dimensions can be used to adjust the reduction process by, in effect, making a slight alteration to the observed readings.  These adjustments do not change the observed values but make slight changes to the co-ordinates that are displayed after the reduction process.

The Lateral dimension, normally L=, can be used to enter a distance by which the observed reading can be adjusted to the left or the right of the line of sight.  This is used in conjunction with the observed distance to make a slight adjustment to the horizontal angle before reduction.  If the dimension is negative, the adjustment will be to the left of the line of sight.

The Horizontal dimension, normally H=, can be used to enter a distance by which the observed reading can be adjusted along the line of sight.  This is used to make an adjustment of the observed distance before reduction.  If the dimension value is positive, the observed distance will be increased.  A check box in the survey instrument settings allows you to specify that this offset is a slope distance, thus adjusting both the co-ordinates and the height.

The Vertical dimension, normally V=, can be used to enter a vertical offset by which the reduced point can be raised or lowered.  If the dimension is positive, the reduced height will be raised by the dimension value.

The circle shape dimensions, Radius, Diameter and Circumference, can also be used to adjust the observed distance.  This can be used where you are surveying to the front of a circular object, such as a tree trunk.  The dimension needs to be entered to size the object but this value can also be used to adjust the observed distance.  The radius can be calculated from the dimension value but will only be applied if specified in the code prefix used by the point.  Refer to the section dealing with the display of shapes later in this chapter.