132
March 2018
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
tional Ellipsoid. The subsequent transformation of the Span-
ish Net to ED50 was based on a two-step two-dimensional
Helmert transformation. The initial step computed by the Axis
(Germans) was still on a Lambert Con-formal Conic projection,
but referenced to the Clarke 1880, which was the standard for
France. That series of collocated points that started compu-
tations in the Pyrenees Mountains was continued into a sub-
stantial portion of the Iberian Peninsula. After the war, the U.
S. Army Map Service decided that the best way to merge the
Madrid Observatory Datum of 1858 into the new ED50 was to
use the existing German data as an intermediate step. In com-
puting the new French datum values of the Spanish triangu-
lation, use was made of the German adjustment of 1938. Val-
ues of the New Triangulation of France (NTF) were available
for the following 11 Spanish triangulation stations: Forceral,
Canigou, Licuses, Rouge, Cabére, Maupas, Anie, Orhi, Baigu-
ra, La Rune, and Biarritz. Computations to the Madrid Datum
of 1858 were performed by V.U.K.A. 631 (April 1943) and by
Kriegskarten und Bermessungsamt, Paris (August 1943).
Other Datums of Spain include San Fernando Observatory
where:
Φ
o
= 36° 27´ 54.6˝ North,
Λ
o
= 06° 12´ 17.8˝ West of
Greenwich. Another version of the same point is where:
Φ
o
= 36° 27´ 41.52 North, and
Λ
o
= 06° 12´ 19.5˝ West of Green-
wich. This same point on the “Salamanca Datum˝ is:
Φ
o
= 36°
27´ 54.65˝ North, and
Λ
o
= 06° 12´ 18.00˝ West of Greenwich.
Pico de las Nieves Datum of 1934 in the Canary Islands is
where the origin is:
Φ
o
= 27° 57´ 41.273˝ North±0.130˝, and
Λ
o
= – 15° 34´ 10.524˝ West of Greenwich ±0.380˝. The defin-
ing azimuth was observed to station Iselta as:
α
o
= 212° 34´
48.30˝
from south
, and the elevation is 1949.14 m. It is ref-
erenced to the International ellipsoid of 1909 (Madrid 1924)
where a = 6,378,388 meters and the reciprocal of flattening (
1
/
f
)
= 297. Also found on the Canary Ise Abona Datum that is ref-
erenced to the International 1909 ellipsoid. The origin of that
Datum is:
Φ
o
= 28° 08´ 22.93˝ North ±0.102˝, and
Λ
o
= – 16° 25´
01.92˝ West of Greenwich ±0.105˝. The defining azimuth was
observed to station Roja as:
α
o
= 221° 48´ 27.48˝”, and the ele-
vation is 16.82 m. The Royal Spanish “Servicio Geografico del
Ejercito” (Army Map Service) Grid of 1945 for the Canaries is
on the International 1909 ellipsoid. The Latitude of Origin (
f
o
)
= 28° 30´ North, and a Central Meridian (
λ
o
) = –12° 00´ West
of Madrid (therefore,
λ
o
= –15° 41´ 14.546˝ West of Greenwich).
The Scale Factor at Origin (mo) = 0.9999244799, and the False
Northing (FN) and the False Easting (FE) = 400 km.
Interestingly, the British Grid system for the Canary Islands
used during WWII by the Allies was also based on a secant
Lambert Conformal Conic projection. The Latitude of Origin
(
f
o
) = 27° 00´ North, and a Central Meridian (
λ
o
) = –17° 00´ West
of Greenwich. The Scale Factor at Origin (mo) = 0.9993817, the
False Northing (FN) = 100 km, and the False Easting (FE) =
200 km. This Grid was referenced to the Clarke 1880 ellipsoid
presumably because the Canary Islands are so close to Africa.
That ellipsoid is/was the (British) standard for that continent.
(Some of the WWII-era British Grids were based on ersatz Da-
tums “cooked up” for reasons of expediency during the war.)
The Balearic Islands in the Mediterranean Sea are said to be
on the Madrid Datum of 1858, but I do not think that is true.
Ten years later, station Mola was observed for the Balearic Is-
lands Datum of 1868 where:
Φ
o
= 38° 39´ 53.17˝ North, and
Λ
o
= +5° 13´ 19.94˝ East of Madrid (therefore, +1° 32´ 05.394˝ East
of Greenwich). The longitude is also defined as –0° 48´ 11.26˝
West of Paris, which leaves a discrepancy of 2.71˝ in Longitude
between Greenwich and Paris. This is not a large error for an
“Astro” shot done on an island in 1868, but it is quite large
for the relation between two national observatories. The defin-
ing azimuth was observed to station Furnas as:
α
o
= 177° 39´
11.03˝
from south
, and to station Camp Vey as:
α
o
= 160° 15´
40.48˝
from south
. The elevation of Mola is 192.25 m, and, of
course, the ellipsoid of reference is the Struve 1860.
NIMA lists the three-parameter datum shift from the Eu-
ropean Datum 1950 (in Spain) to WGS84 as:
Δ
X = –84m ±
5m,
Δ
Y = –107m ± 6m,
Δ
Z = –120m ± 3m, and is based on an
18-station solution.
U
pdate
The National Geodetic Network of GNSS Reference Stations
(ERGNSS) Descriptive information: Currently 75 stations
make up the network, of which 24 are integrated into the
Europeannetwork of
nd3 (YEBE,MELI andLPAL) in
the global network of the IGS
. In
addition, in order to make a more efficient management of
expenditure and with a view to having an adequate density
of stations throughout the national territory, the IGN shares
the ownership of some stations of the ERGNSS with other
institutions, such as Autonomous Communities and Ports of
the State. , through collaboration agreements. The stations
are equipped with multi-frequency geodetic receivers, with
reception capacity of other constellations, such as GLONASS
or GALILEO and geodetic antennas, almost all “Choke ring”
type and with calibration of the phase center variation (part of
them with individual calibrations).
The network of permanent stations of the IGN is the ba-
sic reference that gives access to the ETRS89 system direct-
ly. The objectives of this network can be summarized as:
•
Obtaining very precise coordinates and speed field in all
points of the network.
•
Contribution to the definition of the new
in the national territory.
•
To be fundamental points of the
for the densification
of global frameworks and definition of the ETRS89 system.
•
Use of continuous data records for studies ofGeodynamics,
troposphere, ionosphere, meteorology,
etc
.
•
Define a fundamental network as support for real-time
applications of differential corrections (DGNSS) and RTK.
•
To provide GNSS users, publicly, data for geodetic,
cartographic, topographic and positioning work in general.
In order to make a more efficient expenditure management
