updated: 21-Sep-2010

 Copan for Windows

Distance and Offset Expressions

A fairly sophisticated set of options exists for entering distances (radii or lengths) into Copan. A similar set of options also exists for entering offsets, where an offset is a relatively short distance left or right of, and perpendicular to, a particular bearing or line.

You can enter distances and offsets explicitly as values or implicitly as being the distance between two specified coordfile points. You can even include a simple arithmetic operator in an expression to add, subtract, multiply or divide a distance or offset by another value. An offset is always prefixed with an L, R, or + character.

Syntax

In these quasi-formal syntax definitions, a defined term (outdented) is followed by its definition (indented), with alternative definitions on separate lines or separated by vertical bars. Puzzled? See the Examples.

offset-expression
offset-prefix   distance-expression
distance-expression
distance
distance   operator   quantity
distance
quantity
implied-distance
operator
+ | | * | /
implied-distance
from-point-number   ,   to-point-number
,   to-point-number     (valid if the from-point-number is already entered in an appropriate from-point field)
offset-prefix
L | R | | +     (the prefix is always required)

Examples

In the following tables, note that case doesn't matter and that spaces are not required. Also, assume that point 102 is at a distance of exactly 25 from point 101.

Table 1:   Distance Expressions.
Expression Distance Explanation
10.2 10.2 explicit distance
10 + 2 12 distance plus distance
10-2 8 distance minus distance
10*3.5 35 distance times factor
10/2.5 4 distance divided by divisor
101, 102 25 implied distance from point 101 to point 102
101,102+6 31 implied distance, plus distance
101,102/5 5 implied distance, divided by divisor
, 102 25 implied distance from point 101 to point 102
, 102 -4.5 20.5implied distance, minus distance

For the last two expressions, assume that 101 is already in an appropriate from-point field.

Table 2:   Offset Expressions.
Expression Offset Explanation
+ 3.5 R 3.5 offset right, explicit distance
L 5 L 5 offset left, explicit distance
-5 L 5 offset left, explicit distance
R6.4/2 R 3.2 offset right, distance divided by divisor
r101, 102 R 25 offset right, distance implied (from 101 to 102)
l 101,102/2 L 12.5offset left, implied distance divided by divisor
r , 102 R 25 offset right, distance implied (from 101 to 102)
+ , 102 / 5 R 5 offset right, implied distance divided by divisor

For the last two expressions, assume that 101 is already in an appropriate from-point field.

updated: 21-Sep-2010