Dear Maurizio.
Directly or indirectly GPS was used and is in fact one of the most efficient
and precise surveying technology to determine or bring forward coordinates.
It is only a surveying tool and methodology. A different formulation of your
question is 'could boundaries be defined by coordinates'. It is a matter of
practicality but also with secured legal validity in this modern era.
Borders could be delineated in different ways, verbally as in treaties,
graphically on maps, as usually also attach to treaties, or physically by
border markers. One modern way of defining the border line verbally in
treaties is to base it on geographic coordinates of the border line turning
points, with reference to a common border (geodetic) datum, the reference
frame of which should be secured. Examples are delimitation of maritime
boundaries in terms of geographical coordinates in the WGS-84 datum, the
GPS-related reference coordinate system. What about land boundaries?
Coordinates were used in the past to define border lines, not border points,
like the 141 degrees east longitude for the border line between Indonesia
and Papua New Guinea or the 4 degrees 10 minutes latitude border line
between Malaysia and Indonesia in the eastern part of Borneo. As these were
defined in old treaties, these were accepted to be astronomical geographic
coordinates. To delineate these border lines in the field one could only be
as precise as the available surveying technology allows. The reference frame
are the stars with their astronomical coordinates. Related to delineating
the border line based on astronomical coordinates the refraction factor is
also one of the main error sources and positioning results reliability will
be to meters down to tenths of meters. In the Indonesia - Papua New Guinea
case the new border line was defined to be the position of the (141 degrees
east longitude) Main Markers of the border, determined by
geodetic-astronomic methods, and the geodesics (lines) between these
markers.
One can delineate the border line directly in the field by placing border
markers and defining the border line to be straight lines or another type of
line between these markers. For legal security puprposes a treaty will
always be needed, delineating the border line verbally. If not demarcated
before, verbal delineation in treaties will always be realized towards
delineation in the field, i.e. demarcation of the border line. The location
or position of border markers can and were in the past mosly secured by
witness markers, so one can reconstruct border markers when displaced or
lost. Fixing the border markers with coordinates will provide another
recontruction facility and using GPS one can stake-out the poisition of the
lost border marker to cm accuracy, provided the stations of the common
border datum reference frame is safely secured and maintained.
If one decide in substituting river thalwegs with river median lines
permanently, these in cases of non-navigable rivers or seasonal watered
rivers where thalwegs are difficult to locate or seasonally or overnight
after a heavy rain and storm changing its route, the modern and sensible way
is to delineate the border line in terms of geographic coordinates of the
turning points of the median line, which for practical purposes should be
defined as a traverse of straight line segments. In this case defining the
turning points of the border line with coordinates is a must. The river may
change its course but the permanent agreed 'river median line' border line
could always be staked out and located. Note: Equitbale uses of the river
water by the local community on both side of the border will of course
always be arranged by agreement, whether it is a thalweg or median line in
the river bed.
One has experienced that border markers were displaced using heavy
equipment, mostly in remote areas, and the landscape could be changed in
matters of weeks using heavy bulldozers. A dense rain forest area could in
matters of months be gone and left with open space to some kilometers. But
one cannot move coordinates. These could only be moved if one manipulate the
stations of the common border datum reference frame, which is most unlikely,
as the stations are located on both sides of the border, and relocating
border points should be done jointly. Another preventive measure in this
modern time is to linked the common border datum reference frame to the
WGS-84 reference frame, which is nowadays related to the ITRF (International
Terrestrial Reference Frame) of a certain epoch.
As to accuracies, of course coordinates determined for the points do have a
certain reliability, fixed with surveying or geodetic type GPS technology,
to some cm or dm accuracy, much smaller compared to the size of the border
markers. But to be put in border treaties one have to ignore the accuracies
and the coordinates have to accepted to be absolute values. A heavy
repsonsibilty is so put on the shoulder of the surveyors. That is why one
has to specify standards of accuracies in advance and design survey
technical specifications to meet these. I would like to also refer to advice
from the late Prof. Rinner of Austria to surveyors, i.e. 'What is not
controlled should be treated as wrong'. Redundant measurements are a must to
surveyors to exercise control.
Present available international terrestrial reference frames and available
surveying technology provide a very secure alternative, i.e. to
unambiguously define border lines with geographic coordinates of the border
line turning points. With the fast changing land-scape by human intervention
'geographic coordinates' is the solution.
Sorry for the somewhat extensive discourse for explaining my arguments for
coordinates for boundaries.
Regards,
Klaas Villanueva
----- Original Message -----
From: "Maurizio Morabito" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, May 15, 2003 4:13 PM
Subject: Re: INT-BOUNDARIES Digest - 15 Apr 2003 to 13 May 2003 (#2003-9)
> Pardon me, this surely is an amateurish question, but
> is there any project to use GPS to define boundaries?
>
> I am sure there would be plenty of space in the future
> for arguments about centimeters of difference
>
> regards
> maurizio
>
>
>
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