Coordinate systems

The portal has to know which coordinate system your positions are in before it can place your lines and state where each source is.

Surveys from any country

Surveys from any country are accepted, whoever your organisation is: Papua New Guinea, New Zealand, Africa, the Americas or anywhere else. Your positions only have to be in a coordinate system with an EPSG code (UTM on WGS 84, a national grid, or longitude and latitude). Your files and results are stored in Australia (Sydney), wherever the survey was flown (Your data).

The public map layers (deposits, mines, permits and geology) are Australian. Outside Australia the map still shows your lines and grids on the base map, but those layers have nothing to show there.

Declared systems

Many files say which system they use: in the ASEG-GDF2 definition or its .des, in a .ddf description file or line database, in a Geosoft database, or in the column names. A system named exactly as EPSG names it (for example "WGS 84 / UTM zone 55S") counts as declared. When the portal finds a declared system it uses it and says so: "Located in GDA94 / MGA zone 53, as the file declares." When a file holds two sets of eastings and northings, a declared set is used before an undeclared one.

Always look at the map: the lines should sit where your survey was flown. If they do not, choose another system under Not the right system? Choose another. Go back to what the file declares undoes your choice.

Undeclared systems and the picker

When the file does not say, the portal asks you to choose: "Your file does not say which coordinate system its eastings and northings are in." Search by name or by EPSG code, then click the system. Your survey contractor's logistics report names it.

Any other system with an EPSG code can be found by its name or code in the same search.

If the file has several sets of eastings and northings and none declares a system, you must choose before you can continue.

Longitude and latitude with no datum

Longitude and latitude are only exact when you know the datum they are on. When your file places its stations by longitude and latitude and does not say which datum they are on, the portal asks: "Your file gives positions as longitude and latitude but does not say which datum they are on." Choose one of:

• GDA94, used by most Australian surveys from 2000 to 2020;
• GDA2020, used by most Australian surveys since 2020;
• WGS 84, often the datum of raw GPS positions, and the usual choice for a survey outside Australia.

GDA94 and GDA2020 are Australia's datums: for a survey outside Australia, choose WGS 84 (or give the system of its eastings and northings).

Your survey contractor's report names it. Nothing can be submitted until you choose. The portal then places the lines on that datum's map grid (MGA, or UTM for WGS 84) in the zone of the survey, and every result file states the choice: "The survey file did not say which datum its longitudes and latitudes are on; GDA94 was chosen when it was uploaded." If the file also has eastings and northings whose system is not declared, you may choose their coordinate system instead.

A file whose only positions are longitude and latitude is accepted the same way.

Grids

A grid's header usually names its system (for example MGA54 on GDA94, SUTM55 on WGS84 for UTM zone 55 south, PNGMG55 on PNG94, or NZTM on NZGD2000). When it does not, the portal asks you to choose the system before the grid can be shown on the map. A grid that names a system we do not recognise cannot be used: contact support.

Mislabelled zones

Before a line is prepared, its positions are checked in the chosen system: they must fall inside the area that system covers (in any country), and within 1 km of the file's own longitude and latitude where the file has them. A file declared in one zone whose eastings are in another (MGA, UTM or a national grid) fails this check. When the longitudes point to a different zone, or the latitudes to the other hemisphere, the portal says "the zone looks mislabelled" and offers Use ... with the right system as one button.

Without longitude and latitude in the file, a zone that is wrong but still lands inside the area its system covers cannot be detected automatically. The map is the check: look at it.

Local and mine grids

Positions on a local or mine grid have no standard code. The portal says "The coordinates in this file are on a local or mine grid" and the lines cannot be processed until we set up the conversion to a map grid with you. Contact support and have ready at least three, preferably four or more, points known in both the local grid and a map grid (GDA94 or GDA2020 / MGA).

GDA94 and GDA2020

GDA94 and GDA2020 are different datums, and the same easting and northing means a slightly different place in each. Choose the one your file is actually in, as your contractor's report states; the two cannot be told apart from the numbers alone. Older surveys may be in AGD66 or AGD84 (AMG); those are accepted, and their results are delivered in the survey's own grid.

The coordinate system of your results

Results are delivered in one of these, set for your organisation by us:

• the survey's own grid (the usual choice, and always available);
• GDA2020 / MGA (easting, northing);
• GDA2020 longitude and latitude;
• WGS 84 longitude and latitude;
• WGS 84 / UTM in the survey's own zone (easting, northing).

The two GDA2020 choices are for surveys in Australia only (with its islands, such as the Torres Strait islands, Christmas, Cocos, Norfolk and Lord Howe). For a survey outside Australia they are not offered; if your organisation's setting is a GDA2020 one, the results of that survey are delivered in the survey's own system, and every file says so.

Every file states which system its positions are in and how they got there: the report under its table of sources, the CSV on a line starting # coordinates:, the GeoJSON in its coordinate_statement, and the section figure in its description. When positions are converted from GDA94 to GDA2020, the conversion uses the official ICSM GDA94 to GDA2020 conformal and distortion grid and the file says so, with the conversion's stated uncertainty. For a survey on GDA94 or GDA2020, WGS 84 is taken as equal to GDA2020, and the files say the two differ by up to about 3 m. A survey on another country's datum (for example PNG94) is converted to WGS 84 by the published transformation between the two for the survey's area, named in the files with its stated uncertainty; where no single published transformation covers the survey, the results are delivered in its own system. Positions along the line are never changed by a conversion.

A survey in AGD66 or AGD84 is delivered in its own grid only. To change your organisation's setting, contact support.