PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
January 2018
11
• 10
-4
– 0.40987 Δ
l
• 10
-4
+ 0.03866 Δ
f
2
• 10
-8
– 0.03971 Δ
f
Δ
l
• 10
-8
– 0.01008 Δ
l
2
• 10
-8
+ 0.002454 Δ
f
3
• 10
-12
– 0.00186
Δ
f
2
Δ
l
• 10
-12
– 0.000978 Δ
f
Δ
l
2
• 10
-12
+ 0.0016 Δ
l
3
• 10
-12
.
Furthermore, Δ
f
=
f
M
–
f
o
and Δ
l
=
l
M
–
l
o
where the units
are in arc seconds and
f
o
and
l
o
represent the coordinates of
the Manchurian System of 1933 origin point (listed above).”
The CBLS established the Nanking Datum of 1935 where:
Φ
o
= 32° 04´ 19.7445˝ North, Λ
o
= 118° 50´ 18.5354˝ East of
Greenwich. A Gauss-Krüger Transverse Mercator Grid is
defined at the Datum origin. The scale factor at origin (m
o
=
1.0); the False Easting and the False Northing = zero. The el-
lipsoid of reference is the International (also called the Hay-
ford 1909 and the Madrid 1924) where the semi-major axis
(a) = 6,378,388 meters, and
1
/
f
= 297.
In addition to the CBLS surveys and maps, there were
myriad local surveying and mapping activities pursued
throughout the 20th century in the People’s Republic of Chi-
na. For instance, the Chihli River Com-mission used a Grid
for 1:50,000 maps where the Central Meridian is 116° 25´ 24˝
East of Greenwich, the Central Parallel is 37° 20´, the False
Easting and False Northing = zero. What projection? Proba-
bly a Lambert Conformal Conic because of a paper published
by J. T. Fang of the National Geological Survey of China. In
1949, J. T. Fang published a series of papers in
Empire Sur-
vey Review
concerning the Lambert Con-formal Projection as
applied to China. “It has been decided by the Central Land
Survey of China to adopt the Lambert conformal projection as
the basis for the co-ordinate system, and, in order to meet the
requirements of geodetic work, the whole country is subdivid-
ed into eleven zones bounded by parallels including a spacing
of 3 ½ degrees in latitude-difference. To each of these zones
is applied a Lambert projection, properly chosen so as to fit it
best. The two standard parallels of the projection are situat-
ed at one-seventh of the latitude-difference of the zone from
the top and bottom. Thus, the spacing between the standard
parallels is 2 ½ degrees. This gives a maximum value of the
scale factor of less than one part in four thousand, thus re-
ducing the distortions of any kind to a reasonable amount.”
Fang later went on to explicitly list some of the parameters of
the “Fifth Zone” where, “The standard parallels of this zone
are at latitudes 34° 10´ N and 36° 40´N. Thus,
f
o
= 35° 25´
11.84746˝ as referenced to the International ellipsoid (also
called the Hayford 1909 and the Madrid 1924) where a =
6,378,388 meters,
1
/
f
= 297.˝ Example computations are given
by Fang for Fourth and Fifth Zone transformations.
In the late 1970s, I had the bright idea of going into business
as a consulting cartographer. I moved my family back home to
New Orleans and started pursuing the “oil patch” clientele. Lo
and behold, I received a telephone call from Houston about the
South China Sea. The People’s Republic of China tendered bids
for the exploration and development of hydrocarbon resources
(oil and gas) in the South China Sea, and was looking for compa-
nies to perform geophysical exploration of its outer continental
shelf. A U.S.-owned company (identity to remain anonymous),
“cooked up” a specification for a projection and Grid System for
geophysical exploration in the South China Sea. The ellipsoid
(and presumably the Datum) was the World Geodetic System of
1972. However, the projection was chosen as the Lambert Con-
formal Conic with two standard parallels and a latitude of origin
equal to the arithmetic mean of the standard parallels. That
sort of thing will work on a sphere, but on an ellipsoid (WGS72),
it is a mathematical impossibility!
I worked up the two different Grids based on the two exclu-
sive presumptions: hold to the two standard parallels and let
the latitude of origin “float,” or hold to the latitude of origin
and let the two standard parallels “float.” I termed those two
mathematical possibilities as “PRC South China Sea I” and
“PRC South China Sea II.” To this day, I get phone calls to
the effect, “Hey Cliff, ever hear about PRC South China Sea
_XX_
?” It never ceases to amaze me that they actually find
(and produce) oil out there...
There are some traditional Grid Systems associated with Chi-
na. “China Belts I and II” are Gauss-Krüger Transverse Merca-
tor Grids referenced to the Clarke 1880 ellipsoid (ersatz WWII
systems), where the Central Meridians are at 119° (Belt I) and
113° (Belt II). Scale factor at origin = 0.9994, the False Northing
= -2,210,000 meters and the False Easting = 400 Km. These
specifications are part of the “British Grids” and, although rich-
ly romantic in history, they are lacking in
provenance
.
Current Grid Systems attributed to the People’s Repub-
lic of China find their roots in the Russian (USSR) origins
of assistance. For in-stance, the Russia Belts for China are
identical with the UTM specification with the exceptions or
variations that the scale factor at origin is unity rather than
0.9996, and the ellipsoid of reference is the Krassovsky 1940
where the semi-major axis (a) = 6,378,245 m, and (
1
/
f
) = 298.3.
A variation on this is known as the three-degree Belts, and
the location of the Central Meridians are simply a (half) sca-
lar of the six degree belts
U
pdate
“Surveying & mapping datum is a key infrastructure of
national economy, social development, state security and
information construction, an important foundation for
determining natural geographic elements and the geometric
configuration and spatial & temporal distribution of earth
surface artificial facilities, and the initial numerical data for
various surveying tasks and the basis reference for accurate
demonstration of the geographic space distribution in the real
world by making use of map. China’s surveying & mapping
datum consists of geodetic datum, vertical datum, sounding
datum and gravity datum.
Since its founding in 1949, with a view of meeting the
requirements of economic construction, the People’s Republic
of China has set up China Geodetic Coordinate System
(Beijing Coordinate System, CGCS 1954), Huanghai Vertical
Datum 1956 and Gravity Fundamental Network 1957, which
represent the first-generation datum reference system for
surveying and mapping of China.
Since 1980s, China has strengthened upgrading and
reconstruction of the first-generation datum reference system
for surveying and mapping and gradually built a national
horizontal control network consisting of 48,000 points:
