Shift Expressions

It is easy to enter an implied shift from one point to another.

Syntax

In these quasi-formal syntax definitions, a defined term (outdented) is followed by its definition (indented), with alternative definitions on separate lines.

shift-expression: point-number separator point-number; point-number
separator: , | -

The implied shift is always from the first point to the second point. A single point number implies a shift from it to the origin and is rarely used. Puzzled? See the Examples.

Examples

Assume that these points exist:

Point	Northing	Easting	Elevation
1	100	100	10
2	120	110	12
3	130	90

The following shift expressions would yield these shift vectors (the first four all being equivalent):

Expression	Northing shift	Easting shift	Elevation shift
`1,2`	20	10	2
`1 , 2`	20	10	2
`1-2`	20	10	2
`1 -2`	20	10	2
`2 - 1`	-20	-10	-2
`2 - 3`	10	-20	0
`3 ,1`	-30	10	0
`3`	-130	-90	0
`2`	-120	-110	-12

updated: 18-Jun-2009