Bearing Expressions

A fairly sophisticated set of options exists for entering bearings (also known as azimuths or directions). You can enter them explicitly in whole-circle format or in quadrant format or implicitly as being between two named existing points.

Syntax

If you measure angles in degrees-minutes-seconds (i.e., 1 circle = 360°), when entering angles, always use the format dd.mmss. For example, you must enter 24°52'10.5" as 24.52105 and you must enter 30' as 0.30 (or just .3).

If you measure angles in gons or grads (i.e., 1 circle = 400^g), just enter angles as is (e.g., enter 24.52105^g as 24.52105).

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.

bearing-expression: bearing; bearing operator angle; implied-bearing [. 1 | 2 | 3] (where .1, .2 or .3 means add 1, 2 or 3 quarter turns)
bearing: [operator] angle; quad-bearing; implied-bearing
angle: ddd.mmsss; ggg.ggggg
quad-bearing: N | S | E | W | NE | SE | NW | SW; N | S acute-angle E | W (where acute-angle is < 1 quarter turn)
operator: + | -
implied-bearing: from-point-number , to-point-number; , to-point-number (valid if the from-point-number is already entered in an appropriate from-point field)

Examples

In the following tables, note that case doesn't matter and that spaces are not required. Also, the bearings are north-based.

Table 1: Degrees-Minutes-Meconds Bearing Expressions.

For the last few expressions, assume that point 102 is at a bearing of exactly 35° from point 101.

Expression	Bearing	Explanation
`10.5613`	010°56'13"
`-10`	350°
`24 - 2`	022°
`s`	180°
`E - 10`	080°
`w+5`	275°
`n 35 W`	325°
`s 3 e +0.38`	177°38'
`s 4 w`	184°
`sw`	225°
`101, 102`	035°
`101, 102 .1`	125°	add 090°
`101, 102 .2`	215°	add 180°
`101, 102 .3`	305°	add 270°
`, 102`	035°	if `101` is already in an appropriate from-point field
`, 102 .2`	215°	if `101` is already in an appropriate from-point field

Table 2: Gons (or Grads) Bearing Expressions.

For the last few expressions, assume that point 102 is at a bearing of exactly 35^g from point 101.

Expression	Bearing	Explanation
`10.5613`	010.5613^g
`-10`	390^g
`24 - 2`	022^g
`s`	200^g
`E - 10`	090^g
`w+5`	305^g
`n 35 W`	365^g
`s 3 e +0.38`	197.38^g
`s 4 w`	204^g
`sw`	250^g
`101, 102`	035^g
`101, 102 .1`	135^g	add 100^g
`101, 102 .2`	235^g	add 200^g
`101, 102 .3`	335^g	add 300^g
`, 102`	035^g	if `101` is already in an appropriate from-point field
`, 102 .2`	235^g	if `101` is already in an appropriate from-point field

updated: 18-Jun-2009