Coordinates

Digit groups

Numbers are shown in three-digit groups separated either by commas or non-breaking spaces: use non-breaking spaces (before and after the decimal point) if the number is 10 or more digits before the decimal place or 6 or more digits after. Non-breaking spaces can also be used at the discretion of the writer when commas are used to separate multiple coordinates. See the examples provided in this topic.

Elevations and RLs

Heights are expressed as the distance above or below a known datum. The datum can be locally defined (known as a reduced level or RL) or mean sea level at a specified location. In either case, the datum needs to be defined, e.g. “local mine grid” or “metres above mean sea level at Padang, West Sumatra (amsl)”. See the examples provided in this topic.

Geographic coordinates

There are two accepted formats for geographic coordinates: degree-minute-second (DMS) and decimal degrees (DD). Use the format that is consistent with your sources of data. In general, the DD format is preferred in GIS and geophysical applications. See the examples provided in this topic.

Axis and units

Use abbreviations only if you are certain the audience will understand them, otherwise spell out the axis or reference name in full. The symbol of measurement after the number can be omitted if there is no possibility of misreading. And be sure to observe the rules of formatting symbols (see Symbols).

With cartesian coordinates, separate the metre symbol from the axis label with a non-breaking space. With geodetic coordinates, the metre symbol can be omitted, and with geographic coordinates in decimal degrees, the degree symbol is usually omitted.

Spelled-out axis labels (such as north, latitude, elevation) are not capitalized.

Negative coordinates

Always use an en dash (–) to indicate a negative number. Use positive and negative (with an en dash) longitudes and latitudes in preference to positive E or W of 0° long. (Greenwich) or positive N or S of 0° lat. (equator), unless this conflicts with your source.

Order of coordinates

It is conventional to show latitude first in a geographic coordinate and east first in cartesian and geodetic coordinates.

Datum and projection

The applicable datum and projection must be defined either with each coordinate, or, if there is no possibility of misunderstanding, the datum can be defined for a table, a section, or for the entire document, or as frequently as is required in the text to ensure the reader knows which datum is applicable.

For example, if all coordinates in the document are in the local cartesian grid system, and the reader is familiar with the local cartesian grid system, then you only need to define this early in the document—preferably in a section of the report dedicated to definitions and conventions. However, if a second coordinate system is also quoted, or the readership is wider than just on-site personnel, then care must be taken to ensure there is no possibility for misunderstanding.

Examples

Cartesian

2 390.2 m E, 451.7 m N, –382.4 m RL [mine grid]

below 1,500 m RL...below the –2,560 m elevation….below 900 m amsl

at the 1500 level [this is a label, not a coordinate]

south of 134,200 m N...located at 1,113.45 E...located at 1 113.452 32 m E...located at 1 113.45 m E, 1 466 000.00 m N

a northing of 134,200

Geodetic

...all coordinates are geodetic relative to MGA94 Zone 54,...south of 5,134,200 N...

...at 758 053.31 east, 5 828 497.50 north (MGA94, Zone 54)...

Geographic

–37.654 451 444 latitude, 143.925 190 55 longitude (DD is preferred)

–42° 48’ 05.33” lat., 128° 01’ 49.81” long. (preferred DMS format)

42° 48’ S, 128° 01’ E (alternative DMS format)

Tabulated

All coordinates are relative to MGA95 Zone 54 datum