out obsolescence of a map or group of maps rather than on a fixed time cycle. Obsolescence is deter- 
mined usually by comparing the existing map with current aerial photographs, which may or may 
not have been taken for this purpose. Generally, a map is considered a candidate for revision if 
one or more major features or three or more minor features show established "minimum changes". 
rder The revision criteria are listed in tables 1 and 2. 
can 
Feature Description Minimum Conse change 
—— _— required for revision 
uracy Roads, major Interstate and highways 1 mi/quad (less if needed for 
Ath of 4 lanes or more continuity with adjoining sheets) 
ude- Roads, minor Any road symbolized with 5 mi/quad, with no segment 
a few a double line less than 1 mi 
re- 
di ce Drainage, double-line Perennial or intermittent 1 mi/quad 
provi- Drainage, single-line Perennial 5 mi/quad, with no segment 
less than 1 mi 
Reservoirs Water storage with con- 1 mi in length and covering 
= Eufs trolled outlet 0.25 mi? 
iat every Airports Major landing fields New runways or additions 
flight over 0.5 mi long or pattern 
ght of change 
Strip mines Disturbed earth, active Areas over 0.25 mi 
or inactive 
to obtain Urban-suburban Areas in or surrounding Streets and buildings covering 
a mini- metropolitan areas 0.125 mi? area 
thin. 
n no 
strate- : : : im 
Table 1.- Major features to be considered in evaluating a map for revision. 
(One or more features showing minimum change justify revision). 
hic, 
by 
itho- Mini hange 
Feature De a. mum change 
mme" zone Description required for revision 
uad, 
d by Ponds Stock tanks, private ponds 8/quad having average width 
of 200 ft 
Airfields Private landing fields 1 or more, any size 
oduced Industrial sites Large manufacturing or 100,000 ft2 of buildings 
diazo commercial areas ; 
t area Woodland Major timber areas or Total of 2 mi? of addition or 
ed to orchards deletion, excluding sections 
tion of 1 mi? or less 
as . . . 
Miscellaneous line Pipelines, transmission 5 mi/quad, excluding seg- 
ess features lines, ditches, etc. ments less than 1 mi. 
Limi- 
ular : : 
Table 2. - Minor changes to be considered in evaluating a map for revision. 
(Three or more features showing minimum change justify revision). 
of 
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