USGS Topographic Maps
D. Richey
Purpose
46ºN
NEHALEM RIVER
History
Although the USGS was preceded by four great civilian and military
surveying efforts, including the General Land Office, none had the broad
spatial extent or national mandate given in its enabling act. The purpose of
this surveying program was to be: “...the classification of the public lands,
and examination of the geological structure, mineral resources, and products
of the national domain.” 158 To further this purpose, the Topographic Branch
of the Survey was created in 1938, and the map products of this branch are to
this day more identified with the USGS than any other of its numerous
activities. In 1980 the National Mapping Division was formed from the
Topographic Division and others, and now oversees the maintenance and
management of topographic map production.159
Initially, information for the production of topographic maps was
collected by field survey crews, who relied on the placement of physical
benchmarks on the landscape, survey towers, tape and compass traverses,
and aneroid barometers for determination of elevation.While the Survey
began experimenting with the use of aerial photography in 1902, it was not
until 1933 when the Survey was called upon to assist the Tennessee Valley
Authority that aerial photography came into standard use for the production
of topographic maps. With the launching of the Earth Research Technology
Satellite (ERTS-1, later known as Landsat) in July of 1972, the Survey
moved into the age of remote sensing and digital technology.158 Even with
these advances, by 1988, only 70% of the United States and its territories
were covered by USGS topographic maps published at the commonly used
7.5 minute scale. To this day, most digital maps compiled by the Survey are
compiled from existing analog maps. These digital maps are stored in the
National Digital Cartographic Database, and consist of two types, Digital
Line Graphs (DLGs), representations of data usually associated with topographic maps; and Digital Elevation Models (DEMs), matrices of elevation
for regularly spaced points across the earth’s surface.159
Methods and Products
Since 1882, the USGS has organized its mapping efforts by geographic
coordinate lines, based on degrees of latitude and longitude. The Survey
publishes maps in rectangular format, called a quadrangle map. Because the
longitudinal (vertical) meridian lines converge at the poles, quadrangles are
most square at the equator, and become proportionally more trapezoidal
towards the north and south poles. Due to this, quadrangles closer to the
poles cover a smaller area of the earth’s surface than do quadrangles closer to
VANCOUVER
120ºW
121ºW
HOOD RIVER
VANCOUVER
YAMHILL RIVER
124ºW
GOLDENDALE
THE DALLES
OREGON CITY
MOUNT HOOD
45ºN
45ºN
CORVALLIS
NORTH SANTIAM RIVER
MADRAS
SALEM
EUGENE
1:250,000
30-minute
1:125,000
BEND
44ºN
44ºN
OAKRIDGE
LaPINE
ROSEBURG
CRESCENT
DIAMOND LAKE
CRESCENT
(a)
122ºW
123ºW
ROSEBURG
1 degree x 2 degrees
1:250,000
BROTHERS
CHRISTMAS VALLEY
121ºW
COTTAGE GROVE
43ºN
30 minute x 1º
1:100,000
PRINEVILLE
44ºN
1:1,000,000
WRB Boundary
STEPHENSON MOUNTAIN
BEND
McKENZIE RIVER
122ºW
45ºN
15-minute
1:62,500
43ºN
120ºW
S
123ºW
7.5-minute
1:24,000
CONDON
N
124ºW
Topographic maps, depictions of the land surface features of an area,
published by the U.S. Geological Survey (USGS) represent an easily obtained and inexpensive source of landscape information. USGS topographic
maps are used by a range of citizens and professionals in public and private
sectors for tasks such as site and regional planning, natural resource land
management, environmental monitoring and planning, national defense, law
enforcement, and outdoor recreation. Topographic maps portray a range of
natural and cultural features. Some of the data used to create this atlas, such
as topography, hydrology, and geology, originated with the USGS.
122ºW
123ºW
124ºW
46ºN
(b)
43ºN
Figure 211. The nested scales of quadrangle maps produced by the
USGS in relation to (a) index map to 1:1,000,000 and 1:250,000
USGS quads intersecting the WRB, and (b) the geographic coordinate
system .
Topographic maps portray the shape and elevation of the landscape
primarily though the use of contour lines. A contour line is a line of constant
elevation above (or below) a specific reference elevation, in this case mean
sea level. Contour lines never cross, although intermediate contours merge in
steep terrain, and may form loops. Contours are placed at regular vertical
intervals, usually 20 feet, though they may also represent 5- 10- or 40-foot
(1.5- 3.1- or 12.2-meter) intervals on a 7.5 minute quadrangle, with a bolder
lined index contour every fifth line, or 100 feet, to facilitate orientation.
Supplementary contours, portrayed as dotted lines, indicate 5-foot intervals
in flat terrain. Benchmarks, represented by a black X, are points of elevation
known with greater certainty. They are established by methods compatible
with geodetic accuracy standards, and are physical markers on the ground.
Spot elevations, less accurate than benchmarks, supplement the contour lines
to plus or minus 3/10 of the contour interval. National map accuracy standards permit up to 10% of points tested to be more than 1/2 of a contour
interval from actual elevation, and/or more than 1/40 of an inch (0.6 mm)
horizontally from actual position.160 At the 1:24000 scale of the 7.5 minute
maps 1/40 of an inch equals 50 ft (15.24 m) on the ground.
USGS topographic maps use general color themes to denote various
features (Fig. 212). Contour lines are in brown (and described above), water
features are in blue, cultural features are generally in black, although some
features such as earthen dams may be portrayed in brown as well, and
vegetation is in green. Buildings are represented in two categories, those of
primary human use (filled black squares), and those of secondary use (open
black boxes). Many of these features are edited heavily in urban areas,
defined as areas with over one thousand people per square mile, which have
a pink tint applied to them. Other miscellaneous features represented on
USGS maps include power and telecommunication transmission lines,
pipelines, air facilities, oil and gas fields, and mines. Vegetation is recorded
when it exceeds 20% cover of the landscape for an area greater than one acre
(0.4 ha), and 6 ft (2 m) or more in height - tall enough to conceal troops or
fugitives - with the same consideration for clearings within vegetated areas.
Permanent agriculture such as orchards and vineyards is represented as are
National Parks, Game Preserves, and publicly owned forests.160
Secondary Highway
Light Duty Road
Permanent Agriculture
Figure 210. A comparison of the
coverage of quadrangle scales
produced by the USGS: the highlighted quadrangle north of the
equator covers a greater area than the
quadrangle near the arctic circle.88
Amendments to map from aerial photo
(purple features)
Track/Trail
Urban Area tint
Bench Mark
the equator. In Figure 210, the shaded 15 degree by 15 degree quadrangle
nearer the equator covers more area than the shaded 15 degree by 15 degree
quadrangle nearer the Arctic Circle. Today, the 7.5 minute quadrangle, at
1:24,000, is the standard mapping scale. The map scale defines the ratio
between the measure of a feature represented on the map relative to the
measure of that feature on the earth’s surface; at the 7.5 minute scale, one
inch (2.5 cm) on the map equals 2000 feet (609.6 m) on the ground.88
154
Section Number and Boundary
Rail Spur
Perennial Stream
Ephemeral Stream
Unimproved Road
Index Contour
20’ Interval Contour
Figure 212. Features represented on a USGS 7.5-minute topographic quadrangle map. Scene portrayed is eastern Dallas, OR; 44º55’ N, 123º 19’ W)
PNW Ecosystem Research Consortium
123°15’00"
123°07’30"
123°00’00"
122°52’30"
122°45’00"
122°37’30"
USGS Map Distribution
Box 25286
Denver, CO 80225
or call 1-800-USA-maps
Willamette River Basin Atlas
2nd Edition
NO
RT
H
GA
W
LE
Y
Jefferson
Scio
Sodaville
Waterloo
20
5
Hemlock
122°30’00"
Gates
122°22’30"
122°15’00"
Mill City
OF
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45°00’00"
44°52’30"
122°07’30"
44°45’00"
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121°52’30"
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121°52’30"
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BA
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Gladstone
BA
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Saint Paul
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Lafayette
SO
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205
CO
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Oregon City
FE
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Lake Oswego
RO
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CI
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Happy Valley
EL
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CA
SC
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Scotts Mills
W
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OA
KR
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W
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HO
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213
SW
AM
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PR
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Milwaukie
122°07’30"
M
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Sublimity
EL
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84
122°15’00"
LA
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LY
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99W
SI
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BU
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SN
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Portland
122°22’30"
M
TN
US Geological Survey topographic maps can often be obtained from local
vendors such as bookstores and outdoor supply companies, or can be ob43°22’30"
tained directly
from the Survey at:
122°30’00"
FA
LL
S
58
KE
EL
211
HA
GA
N
Sweet Home
GR
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84
BL
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126
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122°37’30"
22
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44°37’30"
44°30’00"
Oakridge
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Wilsonville
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Creswell
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Yamhill
W
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228
CA
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Sherwood
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SC
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King City
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Tualatin
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219
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240
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Hillsboro
KL
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223
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NO
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Cornelius
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U.S. Highway
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221
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Forest Grove
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Interstate Highway
GR
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Eugene
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Harrisburg
CR
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36
CI
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Banks
122°45’00"
TO
LO
123°22’30"
Adair
Village
CO
TT
AG
E
126
W
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T
Veneta
Corvallis
RI
VE
RS
ID
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NO
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Monmouth
47
47
Scappoose
RE
YN
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43°30’00"
HO
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99W
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26
M
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43°37’30"
Interstate
FO
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Falls City
LO
RA
NE
Philomath
CO
RV
AL
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22
VA
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DA
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Dallas
123°07’30"
LE
M
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123°30’00"
CI
TY
SO
CI
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DO
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45°45’00"
CO
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43°45’00"
GR
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NB
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VA
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FA
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Sheridan
123°15’00"
HA
RN
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S
State Highway
CU
RT
IN
City name & location
CH
ES
HI
RE
KI
NG
S
M
TN
CR
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45°22’30"
VE
NE
TA
W
RE
N
Willimina
RO
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SP
RI
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ER
45°30’00"
123°22’30"
PO
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123°37’30"
M
TN
M
TN
CR
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ND
N45°52’30"
BU
RN
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Primary Arterial
VA
LL
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Minor Arterial
SC
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TS
WRB boundary
CR
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K
name
AMITY Quadrangle
43°52’30"
Quadrangle boundary
FL
AT
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DG
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LA
UR
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18
GL
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BR
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M
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RO
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FA
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22
HO
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PK
SU
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45°37’30"
CR
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44°00’00"
123°30’00"
TO
KE
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123°45’00"
123°37’30"
NO
TI
44°07’30"
M
AR
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NI
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45°15’00"
LE
TZ
PO
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PK
44°22’30"
AL
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BO
W123°45’00"
HI
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LA
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44°15’00"
PR
AI
RI
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44°30’00"
TR
IA
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44°37’30"
W
AL
TO
N
44°45’00"
W
AR
NI
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44°52’30"
VA
LS
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45°00’00"
NO
RT
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S
M
TN
DO
LP
H
45°07’30"
HA
RL
AN
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T
APPENDICES
Map 34. USGS 7.5-minute Topographic Quadrangle Maps
121°45’00"
Saint Helens
45°52’30"
45°45’00"
5
45°37’30"
205
Fairview
Troutdale
219
45°30’00"
26
211
45°22’30"
45°15’00"
Detroit
20
44°22’30"
126
44°15’00"
44°07’30"
44°00’00"
43°52’30"
58
43°45’00"
43°37’30"
43°30’00"
N
121°45’00"
43°22’30"
S
155