1 - NGA

JBcob’s etaff-A single staff or pole used
for mounting a surveyofs compass or other
instrument. sometimes used in place of a
tripod.
Jaderln wlras (ba80 epparatua)-An
apparatus used for base tine
measurement. It consists of sepaala steel
and brase wires, esiended under constant
tenslorr over relerance tripods in the line of
the base. The coefficients of expansion
and tengfhs al a certain temperature of the
two wires having been found, the
temperatures of the wires themselves may
be deduced from the dillerence O! the
measurement of the same distance by the
two wires. With these temperatures known,
the length of the base may be accurately
obtained.
MIL-HDBK-850
Jet Navlgatlon Chart (JNC)--A
1:2,000,000 scale, coordinated series of
multicolored charts, designed to sa!isty long
range navigation 01 high. altitude, hlghspeed
aircratr.
Jolnlng—Connecting two or more separately
~lgltized or stored maps. The junction
between two such maps Is sometimes
visible as a resufl of imperfections or
inconsistencies in the data.
Joint Operatlone Graphic (JOG)—The
standard 1:250,000 scale Depaflmenl of
Defense cartographic product which may
be produced in any 01 the following three
versions to meet the vafidated unified and
specffied commands and mifitery
dapariments area requirements: the JOG/G
(Series 1501 ) Is designed 10 meet ground
use requirements: JOG/A (Series 1501 Air)
Is designed to meet air use requirements:
ard JOG/R (Series 1501 Radar) is the Air
Target Malerial version in support of radar/
intelligence plannicg and operations
requirements.
Jullan calendar—The calendar established
by Julius Caesar in 46 B.C. II is based upon
Ihe assumption thal the true length of the
tropkal yaar was exaclly 365.25 mean solar
days.
J
‘135
Juilan day-The number of aach day, as
reckoned consecutivaty since the ba@nning
01 the presem Jufian period on January 1,
4713 B.C. The Jufian day numbar derrottts
the number of days Ihal has elapsed at
Greanwich noon on Ihe day designated,
sinca this epoch day. Sea also modlfled
Julian day.
junction b8nCtI mark-A bench mark
selected as the oomr’tmn meeting point for
ilnas of tavela or Iinisa 01 levels.
junction detail—A sketch or working
diagram stwawirsgthe details of the various
levelings at a junction.
junction tlgura-A triangulation figure in
which three or more triangulation arcs
meet, or two or more arcs intersect.
}unctlon—1 .[di@lal) The point (node) where
two or more line segments join together.
2.(leveiing) The place where two or n’vxe
fines of levels are connected.