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Now, let’s look at the bottom of the map. Starting in the lower right corner…this
is the name of the map and the year in which the map was published.
The enlargement of this area is the bottom picture. You can see that the map was
photorevised in 1982, meaning that the map was updated from its first publication. All
map features shown in purple represent those changes that took place between 1957
and 1982. When you examine the map, you’ll be able to see that it definitely needs to
be revised again!*
Moving to the left, we see the outline of the state of Arizona with a small black
box inside.
This shows you the location of this Glendale map sheet relative to the rest of the
state. This illustration is especially helpful if the map you are using is from a part of
the country that you are unfamiliar with.*
2
Bottom center of the map is the area showing the map scales. There are two types
shown. There are three graphical scales (look like a ruler and have scale in miles, feet,
and kilometers). There is also a scale called a representative fraction (e.g.,1:24000).
See bottom picture with the red box around it.
The top scale is called a
representative fraction
This scale is read as: one inch on the map represents 24,000 inches on the surface of
the earth. You can use other units, for example, 1 cm on the map represents 24,000 cm
on the Earth’s surface. As you can see, a representative fraction is a dimensionless
quantity, meaning one unit of any type on the map represents 24,000 of the same units
on earth.*
These are the graphical scales (inside the big red-outlined box). They are in three
different units of measure and you’ll use the one appropriate for the questions you are
answering. Examine the mile scale, notice that the scale has ‘zero’ in the middle. This
means that the full length of this scale is 2 miles! Be careful. The kilometer scale is
then 2 km in length and the foot scale represents a distance of 8000’.
Just below the scales you will find the information regarding the contour interval for the
map (small green outlined box). The contours are the lines
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On this map we can see both the contour and index contour lines.
The thick index contours are every 5th line and have reference
elevations marked on them. The index contours also help to make
counting lines much easier since they stand out from the others.
Example, we see two index contours: 1100 and 1125. Given these
two values, we can calculate the contour interval for this map (25’
difference / 5 lines = 5’). Remember, the contour interval can be
read from the bottom of the map below the scales.*
In the lower left corner we have the text which provides us with information on the
techniques used to create the map, organization that produced it, and a key to what
some of the lines and shading colors/patterns mean.*
4
Let’s say that you need information from an adjacent map sheet, i.e., you need to have
the topographic information for the area to the NE of this Glendale map. The names of
the adjacent maps are printed on this map. Let’s look at the NE corner of the map…the
name of the map sheet you would need is “Union Hills Quadrangle”.
There are adjoining maps for all four sides and the four corners. Let’s look at the
bottom of the map…
The three ovals show the locations of the names for the SW corner, SE corner,
and bottom adjoining map sheets (Tolleson, Fowler, and Phoenix).*
Legend Information on Topographic Maps
This information can be found in the appendix of your textbook – Appendix II,
pages A-3 to A-7.
On these pages you will find information of what the various standard colors
mean, along with the various symbols used to distinguish map features and
landforms.
In terms of color:
Brown – contour lines and other topographic features
Blue – hydrographic features (water) or glaciers
Black – features constructed or designated by humans, such as
buildings, roads, boundary lines, and names
Green – vegetation areas such as woodlands, forests, orchards, and
vineyards
Red – important roads and lines of the public land survey system
Gray or red tint – urban areas
Purple – features added from aerial photos during map revision*
5
DETERMINING POSITION ON THE MAP
TWO BASIC TECHNIQUES
•Latitude and Longitude – we worked with this in lab C, and
studied it in the textbook as well as in the online topic module.
•The United States Public Land Survey (USPLS)
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Latitude: These lines run east/west and are used to measure positions north or
south of the equator (0o). Remember that the lines are parallel to each other
hence they are also referred to as parallels. The values can be given with
degrees, minutes, and seconds, followed by the ‘N’ or ‘S’ indicator. <
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Longitude: These lines run north/south and are used to measure positions
east or west of the Prime Meridian (0o). Remember that the Prime Meridian
runs from the north pole, through Greenwich, England to the south pole. These
lines are also referred to as meridians. These values are given in the same
format as latitude, but with a trailing ‘W’ or ‘E’ indicator. Longitude example:
129o23’06”W
*When giving coordinates for a location, latitude is written first, then longitude.*
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