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Missing continent: houses 20 million tectonic plates floating around, colliding and
sliding against each other ??land masses shift over
people, last seen 5 feet to the south. Notice any time, and Australia is no different. Except, Australia?
problem? Yes, the title is misleading and the movement has exceeded that of other continents
adjustment is actually quite small compared due to its unique geology. The last update for the
to Australia? gigantic size of 8,600,000 square geodetic datum, i.e. the 1994 one, corrected its
kilometres. Though, putting in perspective how latitude and longitude by a staggering 656 feet.
points are projected on the Global Positioning
System (GPS), how the continent moves does affect ?ome countries are more stationary than
the accuracy of locating someone, or impair the others. When there is a significant shift in land
ability to differentiate between two neighbouring masses over time we need to revise the models
places. As Australia continues on its journey to the of the Earth from which GPS coordinates are
north, the GPS would be due for a major adjustment calculated, so for example your neighbour doesn't
once every couple of years ??and the next one is end up with your old coordinates,??said Damien
scheduled at the end of this year. Saunders, Director of Cartography for National
Geographic.
The GPS is basically a giant map of our three-
dimensional world. That is, we can know precisely Aside from the adjustment set for the end of
where everyone, everything, every place is by this year, plans have been made for a modernised
simply obtaining three numbers ??the x, y and z datum to be introduced by 2020, in order to
coordinates (or r, 庛, ? in polar coordinates). These keep up with the pace of advancements in
numbers form the basis for a global positioning mapping technologies ??which is probably way
system; by treating the world as one giant grid faster than the rate at which Australia drifts. It?
of coordinates; one can assign numbers to each not that Australia is drifting away so fast the GPS
and every specific place, thus annotating their couldn? keep up ??we know where it is, we are just
respective positions. constantly pushing the very boundaries of precision
and accuracy.
If you would like to know more about the physics
of the GPS, please read Science Focus Issue 10 ?he 憭梁 ??蝷綽?2,000 ??鈭???摰???? 敺?銝 甈???GPS and Its Connection to Relativity??
?曉? ??????5 ??????????暻澆? 憿???瘝??荔??? Cartography, the study of maps and pinpointing 蝡?璅?憿?蝣?????暺?隤?撠?頝?瞉?瘣?860 ??撟單?祇?
locations, is a delicate art. Maps are but static ??蝛???瘥???隤?撌?蝞?銝?鈭? 暻潦? ??敺?????projections of our dynamic, ever-changing world. 摰?雿?蝟?蝯梧?GPS嚗? ??雿????????潘???憭???瞍?Every once in a while, the sets of reference points 蝘餌Ⅱ撖行?敶梢摰???蝣箏漲嚗??成蝷頂蝯勗?颲?used to locate places on the coordinate system ?拙餈暺噫瘣脖?????蝘鳴?GPS 瘥?撟曉僑
have to be updated. These reference points 撠勗?憟賢末隤踵嚗?銝甈⊥?啣??隞僑撟游??脰???constitute a geodetic system which approximates
or defines geographical distances, i.e. the latitude, GPS ?箸銝停?臭?撟楊??銝雁銝??啣?嚗?撠望隤迎?
longitude and altitude relative to these reference ?閬???3 ?摮??單摨扳? x??嚗??璆萄漣璅?
points, and make up the virtual framework on r?詻?嚗停?賜?遙雿犖?隞嗆??圈???蝣箔?蝵柴??啁?
which we overlay the real world on. Usually, these 銵券???箄迂憭雯?潘??策瘥擃?嫣?蝯摮?撠勗隞?reference points are major static structures such as 璅內?詨?雿蔭嚗遣蝡??雿頂蝯晞?roads and electrical grids, surveyed relative to other
existing reference points. However, this implies that ?亥????瘛勗鈭圾 GPS ?????隢霈蝚?10
densely populated areas would be much better ??閮?????雿頂蝯梯??詨?隢?mapped than sparsely populated ones ??in fact,
Alaska is only as well mapped as Mars in this sense! ?啣?摮豢?弦?啣???雿瘜?蝘飛嚗??舐移憒?????[1] ?啣??航??隡?銝?????敶晞???畾菜???靘輯??? ?啣漣璅頂蝯曹葉?冽摰????折????暺??之?唳葫
Now, back to Australia. The current geodetic ?漣璅頂蝯晞??臬???撖虫?????嗆?嚗?靘撠?蝬?datum for the land down under was formalised
way back in 1994. Updates for these datums have
been sporadic ??Australia has only ever seen three
renditions of geodetic datums. Any further changes
to the grid matrix of locations are based on the
1994 datum, minor edits and marks on a stationary
canvas. The thing is, all continents are essentially
