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PHOTOGRAMMETRIC ENGIN EERING & REMOTE SENSING D e c e m b e r 2 0 0 2 1237

THE HELLENIC REPUBLIC

The reg ion of prese nt-day Greece was occu-

pied in the Paleolithic pe riod, and Indo-Eu-

ropean invasions began about 2000 B.C. An-

cient Greece was never unified, but the city-

states o f Athens and Sparta dominated whileother cities shifted alliances over the centu-

ries. Alexander the Great conquered most

of the Mediterranean region and spread

Greek culture throughou t the known world.

However, Greece was conq uered by Rome

in 146 B.C., and by 1456 A.D. Greece was

comp letely under the Ottom an Turk Empire.

Gree ce won its indep end ence from Turkey

in the war of 1821 -1829 , and celebrate s its

Independence Day on 25 March (1821). The

former Kingdom of Greece is now a parlia-

mentary republic; the monarchy was rejected

by referendum on 08 December 1974.

Greece is slightly larger than the state of

Alabama, and it is bordered by

Albania (282 km), Bulgaria (494

km), Turkey (206 km), and

Macedonia (246 km). The low-

est p oint in Greece is the Med i-

terranean Sea, and the highest

point is Mount Olympus (2,917

m).

In 188 9, the Gree k Army Geo -

graphical Service was formed,

and classical triangulation com -

mence d immedia te ly . The

agency name was later changed

to t he Hellenic Military Geog raphical Ser-

vice (HMGS). The initial starting point for

the triangulation was the Old Athens Ob-

servatory where o=3758'20.1" North,

o

= 23 42' 58 .5" East o f Greenw ich, and

was referenced to the Bessel 1841 ellipsoid

where the semi-major axis a = 6,377,397

155 m ete rs and the reciprocal of flattening

1/f= 299 .15 28128. The Yeo grafik Ipires a

Strato map series at 1 :20,000 scale was

produced from 1926 through 1947, and had

the Greek Military Grid shown on some

shee ts. The se ries covered the northernborder and scattered strateg ic areas through-

out Greece. The Greek Military Grid was

based on the Hatt Azimuthal Equidistant pro-

jection, a system o riginally presented on the

sphe re by Guillaumme Postel.

Hatt was the hydrographe r of the French

Navy, and late r taught at a university in Paris.

Apparently he m ade quite an impression on

a Greek student because the Hatt projec-

tion, use d by the French Navy for local grids

of hydrographic surveys, became the national

grid system of Greece in the 20 th century.

The Hatt projection is quite similar to the

Azimuthal Equidistant projections used in

Yem en, Guam, and Micronesia; the d iffer-ences are based on the mathem atics used to

compute the e llipsoidal geod esic for the d i-

rect and inverse cases. Gougenheim, another

French hydrographic engineer, later pub-

lished a number of treatises on the g eod esic

that were later picked up by Paul D. Thomas

who p ublished a treatise for the U.S. Navy

on the sam e subject in the 1970s. Thomas

presented extensive computational proofs

of Gouge nheims work that established the

standard for hand and mechanical calcula-

tor solutions of the geo desic for global ap-

plications of the U.S. Navy. In the 1980s,

Thomas work inspired my research partner

at the University of New Orleans, Dr. Michael

E. Pittman, t o publish his original solution of

the Principal Problem o f Geod esy in the

Surveying and Mapping journal of the ACSM.

The other projection variants mentioned

above for Yem en an d Guam used the ellip-

soidal geodesic solutions developed by Puis-

sant and by Andoyer-Lambert. The Azimuthal

Equidistant for Micronesia was de veloped

by the late John P. Snyde r using the Clarke

Long Line Formula originally de velope d by

Colone l A. R. Clarke of the British Royal En-

gineers (PE&RS, February 1999). Hatts pro-jection was an enormous influence o n Euro-

pean cartography world-wide for many de-

cades, and I am often amused to see con-

tem porary software p ackages list unknown

projections and grid systems a s Systm

Recta ngulaire Usuel with no further infor-

mat ion. That Usual Rectangular System

found worldwide is the Hatt projection! Nev-

ertheless, the only country that adopted the

Hatt Azimuthal Equidistant p rojection as the

national grid was Greece. In 198 0, Brigadier

General Dimitri Zervas, com man de r of the

Hellenic Military Geographical Institute, sent

a treatise to me e ntitled

, 1963(HATT AZIMUTHAL EQUIDISTANT PROJEC-

TION). The 21-page tome was written en-

tirely in Greek by John Bande cas, bu t Gen-

eral Zervas m ercifully penciled -in Eng lish

translations of paragraph headings so that I

could understand the mathematics pre-

sente d. That was my one and only expe ri-

ence w ith Greek geo desy in which the only

thing I could comprehend was the Greek

symbols for standard ge ode tic terms in the

math!

Coordinates later published for the Datum

Origin were o

=3758'18.680" North and

o= 23 42 ' 58.8 15" East o f Gree nwich, but

curiously the National Topo-

graph ic Series published by the

Gree k Military used theAthens

Observatory as the ir national

prime meridian. The m ap se ries

at various scales were based on

intege r minute d ifference s from

the Athens m eridian. The basic

series were based on 30- by 30-

minute blocks with latitudes of

36 30' N to 42 00' N and longi-

tude s of 4 30' W of Athens to

3 30' E of Athens (23 42'

58.815 " East of Greenwich).

The Revised Military Grid used in som e

nation al ap plications after WWII was based

on the Lambert Conformal Conic projection.

Using the same central meridian as the Ath-

ens Observatory, the three tangentzones

had latitudes o f origin of 35, 38, and 41

with False Eastings of 1,500 km, 2,50 0 km,

and 3, 500 km, resp ectively, and all three

zones had False Northings of 500 km. The

Old Military Grid used from 1931 to 1941

had the same parameters except that there

were no false origins.From 1925 to 19 46, the re were two Brit-

ish Grids used by the Allied Forces. The

Mediterranean Zone was a secantLambert

Conical Orthomorphic where the central me-

ridian was 29 East of Greenwich, and the

latitude of origin was 39 30' N, the scale

factor at origin was 0.99906, the False Easting

was 900 km, and the False Northing was 600

km. The Crete Zone was a tangentLambert

continued on page 1238

Grids and Datums

Hatt was the h ydrograph er of th e Fren ch

Navy, and later taught at a university in Paris.

Ap parently he made quite an impression on

a Greek student because the Hatt projection,

us ed by th e Fren ch Navy for local grids of

hydrographic surveys, became the national

grid system of Greece in the 20 th century.

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1238 D e c e m b e r 2 0 0 2 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING

continued from page 1237

Conical Orthomorphic where the central meridian was Athens (24 59'

40" East of Greenwich), the latitud e of origin was 35 N, the scale factor

at origin was 1.0 (by definition of a tangentzone), the False Easting

was 200 km, and the False Northing was 100 km.

There is a ne w reference system used in Greece nowad ays. It is

called the Gree k Geode tic Reference System of 1987 (GGRS87)

where o

=3804'33 .8107 " North, o

= 23 55 ' 51.00 95" East of

Greenwich, No

= 7.0 m , and t he ne w Gree k Grid is based on the

Transverse Mercator p rojection (presum ably Gauss-Krger) whe re

o

= 0, o= 24 E, the False Easting = 5 00 km, and the scale factor at

origin (mo) = 0.9996. Gene rally, I have serious do ubts concerning any

new grid system that use s some non-stand ard variant of the UTM

Grid, but I understand that this particular one was de vised by Profes-

sor Veis of the Technical Univers ity of Athen s. If Professor Veis ap-

proved of this new grid, then there ce rtainly must be a valid techni-

cal reaso n for the curious param ete rs chosen. Thanks for the abo ve

param eters go to Yannis Yanniris, a phot ogram metrist in Athens.

The Nat ional Imag ery and Mapping Agency (NIMA) has p ublished

datum shift pa ramete rs from the European Datum of 1950 in Greece

to the WGS84 Datum where X = 84 m,Y= 95 m, andZ = 130

m; however, this solution is based on only two points and the accu-

racy of the comp onents is stated to be 25 m. Users inte reste d in

geodetic applications of GPS in Greece should read the NIMA

notice published next to my column in PE&RS Octobe r, 2002. The

Europe an Petroleum Studies Group has p ublished shift parame ters

from GGRS87 to WGS84 as being X = 199.87 m, Y= +74.79 m,

and Z = +246.62 m. The EPSG published no accuracy estimate s for

their parameters, so caveat em ptor.

Cliff Mugnier teaches Surveying, Geod esy, and Photog rammetry at

Louisiana Sta te University. He is the Chief of Geo de sy at LSUs Cen-

ter for GeoInformat ics (Dep t. of Civil and Environmen tal Enginee r-

ing), and his geod etic research is mainly in the subsidence of Louisi-

ana and in Grids and Datums of the world. He is a Board-certified

Photog ramme trist and Map ping Scientist (GIS/LIS), and he h as ex-

tensive e xpe rience in the practice of Forensic Photogramm etry.

The content s of this column re flect the views of the author, who is respo nsible for the

facts and accuracy of the data prese nted herein. The conte nts do not ne cessarily

reflect the official views or policies of the American Society for Photogrammetry and

Remote Sensing and/or the LouisianaStateUniversity Center for GeoInfor-

matics(C4G).

Grids and Datums