538
August 2017
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
two datums is that the 1918 re-determination of longitude is:
Λ
o
= 139° 44´ 40.502˝ East of Greenwich, which is an increase
of 10.405”. The latitude was the same for both years. In Ko-
rea, the geographic coordinates of the triangulation stations
are on the Tokyo Datum of 1918, but the Grid coordinates
are on the Tokyo Datum of 1898. This is a little-known fact of
Korean mapping that has led some cartographers to question
their own sanity!
The number of triangulation stations lost or destroyed
during World War II and the Korean War was about 12,000,
or approximately 80% of the marks in South Korea. The re-
arrangement and reconstruction of the triangulation stations
were begun in 1957. Rearrangement in this context means
that work is done to build the stone marker to coincide with
the recovered footing of the original triangulation station. Re-
construction work refers to rebuilding the footing and marker
at the original site, or nearby, and per-forming the triangu-
lation observations anew. All of this work was completed by
1986. In 1975, electro-optical distance meters (EDM) were
introduced to the observational techniques. The re-survey
has been of 1,291 existing first- and second-or-der stations
as well as 14,798 third-and fourth-order stations. This has
resulted in a new geodetic network being established where
the accuracy specification is ±3 cm horizontal, ±5 cm vertical.
The Korean Datum of 1985 origin is at station Suwon on the
grounds of the National Geographic Institute (NGI) where:
Φ
o
= 37° 16´ 31.9034˝ North, Λ
o
= 127° 03´ 05.1451˝ East of
Greenwich. The defining azimuth to station Donghak-san
is: α
o
= 170° 58´ 18.190˝. The ellipsoid of reference did not
change. The 40 Laplace stations established for this new da-
tum were planned for a density of one station per 5,000 km
2
.
By 1996, 37 Laplace station observations were completed.
The civilian Cadastral Grid system will continue on the new
datum with no change in parameters other than the ellipsoid.
The leveling net in Korea was initially established between
1910-15, but the Korean War virtually destroyed all existing
marks in the south. Since 1960, NGI started the re-survey of
its network and by 1986 completed the first-order net. This
is composed of 16 loops and 38 routes with a total length of
3,400 km and 2,030 benchmarks spaced at 2-4 km intervals.
The primary benchmark of the Republic of Korea is at Inha
University in the city of Inchon. Second-order benchmarks
total 4,035 points along 7,600 km of leveling routes.
NGI has used satellite surveying techniques since 1979.
Two Magnavox 1502 receivers were employed at Pusan,
Kyeonju, and Cheju-do through co-operation with Japan until
1982. Twenty islands have been occupied for Transit satellite
observations as of 1991. Since 1991, NGI has been using GPS
receivers to strengthen the classical network. Plans to estab-
lish 20 permanent GPS observation stations in a Continu-
ously Operating Reference Station (CORS) network started
with the first station called SUWN using a TurboRogue
TM
SNR-8000 receiver on March 15, 1995.
Gravity surveys have been con-ducted by NGI since 1975.
The original design plan called for 25 first-order stations and
2,000 second-order stations. By 1996, 1,709 second-order rel-
ative gravity stations had been observed at existing bench
marks. The initial point for the Korean gravimetric datum
is also at station Suwon in connection with the international
gravity datum at the Geographical Survey Institute of Japan.
Auxiliary first-order stations are located at Seoul National
University (
f
= 37° 27.1´ N,
l
= 126° 57.0´ E), at Kyeongbuk
National University (
f
= 35° 53.2´ N,
l
= 128° 36.9´ E), at
Pusan National University (
f
= 35° 13.0´ N,
l
= 129° 05.0’ E),
and at the Korean Standards Institute (
f
= 36° 23.1´ N,
l
= 127° 22.4´ E).
On August 20, 1888, Russia and Korea signed an agree-
ment providing for freedom of navigation on the Tumen
River for coasting-vessels of both nationalities. The treaty
also spoke of the river as “their common frontier.” However,
since Japan annexed Korea in 1910 the status of that com-
mon boundary is not clear. By 1914, Japan submitted a plan
for the delimitation of the boundary by using the Rule of the
Thalweg, but World War I and the Russian Revolution pre-
vented any action.
The Korea “Demarcation Line” at the 38
th
parallel rep-
resents the partitioning of Korea effected by the July 27,
1953 Panmunjom Agreement ending the Korean hostilities.
Approximately 238 km long (148.5 miles), the line follows a
sinuous path over rugged terrain.
The China-Korea boundary received attention in Novem-
ber of 1961 when magazines published in both countries car-
ried features on the Ch’ang-pai mountain range and specif-
ically “The Pond of Heaven” which is a volcanic lake. Both
countries claimed the same lake. The first at-tempt by both
countries to define their common border in this region dates
back to 1713, but disputes and confusion obviously continue.
On January 30, 1974 the governments of Japan and Korea
signed two maritime agreements that established a conti-
nental shelf boundary in the northern part of the maritime
region adjacent to the countries. The boundary is defined
by a series of ellipsoidal loxodromes (rhumb lines) be-tween
points referenced to the Tokyo Datum of 1918. On Septem-
ber 20, 1978 the Republic of Korea promulgated a system of
“straight baselines” by Presidential Decree No. 9162. These
straight lines are also de-fined as loxodromes on the Tokyo
Da-tum of 1918, and Korea defers its boundary claim of ter-
ritorial waters in narrow water bodies such as the Korean
Strait and Cheju Hachyop.
DMA/NIMA lists the three-parameter datum shift from To-
kyo Datum of 1918 to WGS 84 Datum in the Republic of Ko-
rea as: DX = –147m ±2m, DY = +506m ±2m, DZ = +687m .2m,
and is based on a 29-station solution. However, my solution
for nine well distributed first-order points (N’pyong, Hainam,
Namhai, Bangejin, Sokcho, Hansan, Sangju, Uljin, and Kang-
wha) is: DX = –323m ±2m, DY = +309m ±2m, DZ = +653m
±2m. The actual rms fit of my solution to test points is: Lat-
itude = ±2.20m, Longitude = ±1.26m, and Height = ±7.87m.
On the other hand, using a 7-parameter Molodensky model
(with the Datum origin) with these co-located positions yields:
