GDA What is it?

How will it affect you?

Geoproject Solutions © 2002

Australia is changing its mapping and spatial information systems to a new datum – the Geocentric Datum of Australia 1994, or GDA94. Put simply, all coordinates – latitude, longitude, east and north – will alter by between 130 and 170 metres each. This change will take place during the year 2000, and will impact on everyone who uses

• Charts, maps and plans • GIS, CAD, seismic and other spatial data • GPS and other positioning/navigation systems

The changeover has been adopted by both state and commonwealth governments and means, in practice, that all Australians will need to adjust.

The government rationale is to bring our map systems into line with international usage, and with modern positioning technologies, particularly the Global Positioning System (GPS). A point located relative to the new datum will be approximately 200metres south-west of the point denoted by the same latitude and longitude on the previous datum.

Conversion does NOT mean that permits, structures or points will move. However, wherever locations are mapped or stored in latitude and longitude, or in east and north, those coordinate values WILL change. Nor will it affect OWNERSHIP of permits, leases, etc. But it WILL open significant risks of confusion and 200m errors.

COORDINATES OF

The new datum - the base from which coordinates are measured - is named GDA94. Maps based on a UTM projection from this datum will be referred to as MGA94, or Map Grid of Australia. GDA and MGA will replace AGD(84) and AMG respectively.

Prevention is better than cure. With planning, and with assistance where you cannot divert the resources yourself, changeover to GDA is easily managed. Geoproject Solutions hopes this checklist will be useful, and would be pleased to provide any further assistance.

Check list for minimising GDA hassles:

Obligations When mEducation Informat

Make cliManagement systems: Quality sSpatial data stored in GIS or CAD systems:

Can youDetermin

Data being acquired Make susuppliers

Paper charts and plans which you need to continue using

How will

Supplying digital data How willExploration permits Ensure f

licenses

Telephone 0408 905351 gjh@geoproject.com.au

HAY ST

ROBERTS RD

SubiacoOval

AGD84 (AMG) ORIGIN - THE OLD ORIGIN

GDA94 (MGA) ORIGIN - THE NEW ORIGIN

SAME COORDINATES,RELATIVE TO NEW ORIGIN

SUBIACO OVALON CURRENT SYSTEM

TOW

NSHE

ND

139 m

149

m

The change is more than enough to show at street directory scale

ust information to government be GDA-based? ٱ ion for colleagues / staff / management ents aware of your plans

ٱ ٱ

ystem affected? ٱ r GIS/CAD/Seismic software transform? e and publicise conversion date

ٱ ٱ

re datum for incoming data is known. When will change to GDA?

ٱ

they be marked to avoid mistakes by future users? ٱ

recipients be advised as to datum? Changeover date ٱ amiliarity with DM&E schema, especially graticular bounded by regular latitude and longitude values.

ٱ

GDA What is it?

How will it affect you?

Geoproject Solutions © 2002 Telephone 0408 905351 gjh@geoproject.com.au

Preliminary conversion factors This map shows the differences in coordinates at specific locations. Use: Conversion of smaller scale maps and for preliminary check of conversion routines. Intended for maps and data derived from points for which AGD84/AMG positions have been provided by government authorities. Precision (estimated standard deviation) , ±1-2m within 100 km, if used as intended. Other positions: Not appropriate to positions based on other networks, e.g OmniSTAR.

Changes to latitude and

longitude in WA:

From AGD84 To GDA94

Example conversion: AGD84 / AMG Correction GDA94 / MGA Lat. 20° 58’ 57.9” S + 4.8” → 20° 58’ 53.1” S Long 117° 05’ 45.0” E + 4.8” → 117° 05’ 49.8” E E 509963m + 139m → 510102m N 7679748m + 155m → 7679904m (Consider South latitudes as negative – the correction is northerly and therefore positive)

+133m+5.2”Φ

+137m

+4.7”Φ

+4.5”Φ

+5.0”Φ

+4.8”Φ

+4.4”Φ N

+4.4”Φ N

+139m

+139m

+137m

+139m E Important: The differentials shown are only valid within each local area. Please contact Geoproject Solutions for advice on other situations.

+139mE

9 2

Important DATES for GDA94 implementation in Western Australia: Spatial Cadastral Database (SCDB) converted to GDA by DOLA 4 December 2000 Tenement Registers, Department of Minerals and Energy, converted to GDA 18 December 2000 Commonwealth promulgates GDA regulations under Petroleum (Submerged Lands) Act ( estimated date)

May 2002

Website for further information: www.geoproject.com.au/gda.html

Perth +149m N

Changes to coordinates in WA:From AMG (datum AGD84)

To MGA (datum GDA94)

Wyndham N +4.5”λ E

Albany +147mN

Kambalda E +157mN

Wyndham E +165mN

Broome E +160mN

Roebourne E +155m N

Kambalda N +5.2”λ E

Dongara N +5.2”λ E

Broome N +4.7”λ E

Roebourne N +4.8”λ E

Perth +5.3”λ E

Albany +5.5”λ E

Dongara E +150½mN

ZONE 5

ZONE 51 ZONE 50 ZONE 4