Reference Frames in Practice: The Role of Professional, Scientific,
Standards and Commercial Organisations
by Paul Cross, Matt Higgins and Roger Lott
Key words: reference frame, co-ordinate system, datum,
co-ordinate transformation, satellite positioning system.
It is well known that the current, and growing,
trend towards use of satellite positioning systems and global
satellite mapping systems to produce position-based products in a
global reference frame can introduce serious practical difficulties if
the results need to be related to older maps and/or digital data.
Special problems arise, for instance, in the fields of navigation, map
revision, cadastral surveying and geomatics operations to support
hydrocarbon exploration and production.
The difficulty fundamentally arises because of the
need to transform the data into the (usually local) co-ordinate
systems used to describe the older data (or vice-versa). In principle
co-ordinate transformations are a straightforward mathematical
procedures but in practice they can cause serious problems because:
- not all of those who need to undertake this work have a
sufficiently strong (or sufficiently up to date) education in
basic geodesy, and/or
- the distortions and inconsistencies of the local datum are not
sufficiently well known, and/or
- the numerical information needed (including transformation
parameters) is not readily available, and/or
- the language use to describe the various parameters and physical
quantities is not uniform.
This paper reviews the work of a number of
international organisations in solving some or all of these problems.
Special emphasis is placed on the following.
- Scientific bodies such as the International Association of
Geodesy (IAG) and the International Astronomic Union (IAU) and
some of their sub groups and special commissions (e.g. Commission
X of IAG and the IERS).
- The International Federation of Surveyors (FIG) and its many
Commissions and Working Groups - including WG5.5 - Reference
Frames in Practice in which all three authors participate.
- Various International Standards organisations and their
sub-committees (e.g. ISO TC211) and consortia of commercial
companies concerned primarily with formats for data exchange.
It is concluded that there is currently
insufficient co-ordination between the work of the many groups with
interests in this field - but, despite this, progress is slowly being
made, especially in the collection and distribution of information,
education of users and adoption of a common set of definitions.
Professor Paul Cross
Department of Geomatic Engineering
University College London
London, WC1E 6BT
Dr Matt Higgins
Department of Natural Resources
Locked Bag 40
COORPAROO DC Qld 4151
BP Amoco Group