1 - NGA

U.S. control ourvoy nata-’l’he two corrtml
survey nafe bdng extended over the United
stabs by fhe National f3eodefk survey fer the
tird of rrautkaf cAarfe and fcfmgrapfric mapa,
z=d(k~=z”sv
=-d’”””+”” fJ=Wma, afawofwhioflhava
bean Llxullfd by the Unflad stems Geological
Survay. The Corps& Englnaara, arxl other
-~ m date Cfarivd h lfrls survey
are being c&@Lefad and CcrTafatad on the
North A~ datum d 1927. lb Natfcrral
Gacdafk Survey la currently rawrrrpufirrg the
hortsonfaf corrfmf network to the North American
dalwn of 19ss. (2) The Variical amfml cAlrvey
net consisting of tires & firsf-crdar and aacmld.
order spirit bavahg wtrkdr datarrnirre the
ebvatbns of tfrouaarrdsd bansh rmwka nbove
a aernmorr datum, mean aee level. Thb nd
includas times of levels run by the United States
Geobgkal Survey, ha Cape of Enginaem, and
other organizafii.
U.S. Engineer praolso taveling rod- A
~king rat of T-ahepad cmes aasfiotr, 12 bet
*, 9tid In .arrtirnfrters.
U.S. Gaologkal Survey lavet-A level of
~ d- ~, -wed at atah+as ateet. ft
has en infernal fccusing la!aasopw the level
b-e is omfemd by the end-ccrirrckienca
method, affeofad -h t~ aid of s ptfwll dSVi04
and Sfellife mirmr wirkh can be ad@tad by the
observer.
U.S.
rod-1.
Gaologkal
A -tdrm .C––.
SurvoY prods.
d rkduetad
Iermllfrg
in mrde md
hactima deyard. %”rn-&forea&~th&
oruaatvima tothenaaraat thcuaarxifh of ayard.
llw eum of tha three readings is than the mean
raetimg in feet to fha naamst thouacndfh. 2. A
target md of ptus-algn (+) cross aaclkn, a Me
over 12 feat in Iwrgfh. Rrare are two krrrns cd
this rod fhe aingla-fargat rod and the doubkrtergat
rod.
U.S. National Map Accuracy
Sfsndarda-1. Horizontal accuracy: (I) for
~P8 al Publkat”mn scales Iargar than I :20,000,
90 percent of al wall-dafhed faaIurss, with the
exsaptbn of those unavoidably displaced by
exaggerated aynrbcfizatbn, will h foctded Within
1/20 inch (0.8S mm) of their geographic
MIL-HDBK-8S0
u
paffbna as rderrad
fwrraqr at p&fbUon
te the map pmiadkw
scales d l:~,000or
(2)
smaller, I/W) irwh (0.54 mm). 2. Vertmsl
OOparced daffsonfwasnd
elavafti infaplafad from ocmtcum till ba
ascwafe within ena-fmf cffhafmakcorrtour
Ir$ervef. Dkcmpamw “ in ffwcccumcytrf
ccmfcnus and S&vafiona bayond fflk tcl’sransa
-Y ~ -~ by assuming a horizordal
d~m wfthin 1/50 imfr (0.S0 rrun). Alac
called map accuracy standards; national
map ●ccuracy standards.
ultrawlde-angk kna-%a suparwldo-
●ngfo kna.
uncheoked ●pot ekvatlon-Ekvalion
detemrhad by undmakad Wd ew’vay maffrata,
such as eida tis on rladia lima. undmkad
verticai angles, and bammafria iavdkrg. Also an
elevation datarminad by rapealad
photogrammatric raadtrrg.
uncontrolled meaak-(JCS) A masaic
-- ~ uxerraded prints, the derails of
whii have baarr r-na$chad from print to print
withcut grmrnd control or other orientation.
Accurate maasummenf and dimcfkrn cm?rrd ba
asomn@ibhad. see ako controlled moaalc.
undwgmund marfr-A survayinu mark eat
●-d plurrbad below tha Oantar d a eurfase
mark and eapamtad Iharefrorn so as to praserva
t:~~ticm in 0ss0 of acsidari to the aurfaca
undershoot-A data omisabn which coours
during the dats CSpfUm p~m, prdc.shrfy
during rnarrtsrd d@tiirng. In an undershoot
situatbn, baar rkta falls ahwr d rrnsting an
interaaafbn. An undarahool may be oormotad
by a snap dtwam function.
undevsrlopable-A surface, such as a
6phera, that cannef be flattened to forma plane
without compressing er stretchkrg aema part of
it.
u ndo-(dqifal) The ability to cwcel a previous
command to the mmputar.
undulation of the gaold—See geold
halght.
L71