/i Zz*. 
? • I • 1 * \ JL i 
,m lines that arc far apart oflf* 
^ lines that are close together^ 
‘ that mn together indicate a 
p hues express altitude, form, 
I below. 
4? 
va 
that 
s 
betw 
een twt 
, T .,vr 
'1 
3 particular area mapped. 
Surveys of areas in which t 
c importance, such as most o 
Its tributaries, are made with 
publication of maps on a sc? 
9 with a contour interval of 1 
Surveys of areas in which 
c importance, such as mucl 
n of Arizona or New Mexico, 
lc northwest, are made with i 
Publication of maps on a sea 
250JX)0 (1 inch — = nearly 4 n| 
to 250 feet. ■ 
ie aerial camera is now being 
lation recorded on the ph< 
show only drainage and cult 
in the Lnited States. Bv t.lf 
"bus, aerial photographs are i 
egular topographic maps, 
age and culture. . 
i 
topographic surv 
♦ 
near 
percent 
percent 
i 
500,000 
err 
n ear 
it 
scale 
inder 
nearly 4 mi| 
r economic importance, cover 
laps published are on a scale of 
*ger. In addition to the area < 
U» 11 O AA .i 
of -mdi, (1 inch 
