1 - NGA

called double shooting. See also
composltts.
doublo CW’Iter theodollta-see repeetlrrg
theodollto.
.MIL-HDBK-850
doublo conterlng-A method of prolonging a
line fmm a tfxed point whereby the backsight is
taken wlfh the telescope direct. The Instrument
is FJungad, arxt the formighl is made with the
teleempe inverted. The pint et whch the
vertical cross hair intersects Iha hub b Ihen
marked. The lrarraJt la then rotated 10 take a
becka.ight on tha fixad point with the telescope
Invarlad, the foreeighl la made wilh the
iele~pe dlreci, and a second projected poktf is
meilmd on the hub. A point midway between
the two marked points Is the lrue point on the
profongad tine, Atso called double reveralng;
double reversion; double slgh!lng;
reversing In aslmuth and eltltude;
wlggllng-lrr on a Ilne; working-in on a
Ilne.
double cornere— Normally the two sets of
rnmara along e standard parallel; the standard
townsnip, sectiin, and quarter section comers
placed at regular intervals of measurement;
additionally, the closing corners established on
the Ilne at the poims 01 Intersetilon 01 the guide
meridians, range, and section lines of !he
surveys brought in from the south. In olher
cases, not hIlfy in conformity with the rectangular
ptan, two comers, each common to IWO
townships only, Inataad of one comer of the four
tOwnShi@. SimilSrly, two comers, each common
10 two sections, and two quaner section corners,
aach referring to one aeclion only. The term is
eomalimes used incorrectly to denote two fines
established on Ihe ground although the field
note record Irslicates only one fine, thus creating
a hiatus or overlap.
double ●xpossssra-Two photographic
exposures on the same sensitized surface.
double interpolation-Derivlrrg a value from
tatwlared computations where two or three
P~bn6 may be required, as in an hour
angle observation of Polaris for azimuth, where
an interpolation is made suitable to the time
factor, another to arrive al a result conforming
with the latitude of the observing station,
double merldlan dlstancGThe algebraic
sum of the peqzendicular distances from fhe two
ends of any line of a fraverae to the initial, or
reference. marldlan.
76
double model stereofemplat—A templet
representative of the horizontal pbt of MU or
three adjacent stereoscopic models that have
been adjusted to a common, though random,
scale.
double proponlonete meesuroment- A
mathod for restoring a feat wrner of four
townships or a bat imerbr corner of tour
sactbne. If is baaed on tha principte that
monuments nmlh and south should oomrol the
Ialiludinal posilion of a bat mmer, and
monuments aast and wast ahoutd control the
longitudinal position. In this method the
influence of one identified original comer is
baianced by the cmntrol of a corresponding
original corner upon the opposite side of a
particular missing corner whkh is to be restored,
each identified original cnmer being given a
controlling weight inveraefy prmpetilonal to fts
dklame from the bst comer.
doubfa reveralng—See double centering.
double reveralon—See doubla centerlrsg.
double ehootlng—See double burn.
doubla sighting—See double centering.
double target leveling rod-Any target rod
having graduations on two opposite faces.
double zenith dlstenceA value of twice
the zenith distance of an object, obtained by
observation and Mt by mathematical process.
doufzle-projection direct-vlewtng
stereoplotter—A class of stereo-plotters
employing fhe principle of projecting the images
of IWO correctly oriented overlapping aerial
photographs onto a reference datum so the
reaultam images may be viewed directly wllhout
addtiional optical system support. Also called
double optical projection rstereoplotter.
dOUble-rOdded llna-A fine of differential
levels wheraln IWO sets of tumlng peints, one
high and one low, are used to give independem
measures between bench marks.
doubly azlmuthel map projoctlon-An
azimuthal map projection having two poles.
dove prlBftt-A prtsm which reverts the Image
but does not deviate or displace Ihe beam. A