Map Reading and Land Navigation Flashcards
what’s a map?
a graphic representation of the Earth’s surface, drawn to scale as seen from above
what document covers map reading and land navigation?
TC 3-25.26
what’s the purpose of a map?
to provide accurate information about the existence, location and distance between ground features like terrain, elevation, populated areas, routes of travel and communication
what is the scale of a map?
the ratio of ground distance to map distance and expressed in a fraction
how many map scales are there and what are the names?
there are 3 map scales, planimetric map, photomap, terrain model
what is marginal information?
instructions about the maps use, size, area
where is the map sheet name found?
two places: the center of the upper margin and either the right or left of the lower margin
what is a topographic map?
a map that portrays the layout of terrain features, as well as relief, or the vertical distance of the feature . (distance from sea level)
what is a photomap?
an aerial photomap of a portion of the Earth’s surface on which grid lines, place names and approximate scale and direction have been added.
what is a planimetric map?
a map that only shows the horizontal positions of features. it differs from a topographic map in that it omits relief, usually represented by contour lines.
what is a map usually named after?
The most prominent geographical or cultural feature. Whenever possible it is named after the largest city on the map
where is the declination diagram found?
It’s located in the lower margin of large-scale maps
where is a map sheet number found?
In two places: the upper right and lower left margins
Where is the map series name found?
It’s found in the upper left margin
What is a declination diagram?
It shows the angular relationships of true north, grid north, and magnetic north
where is the series number found?
the upper right and lower left margins
Where is the scale of the map found?
In the upper left margin after the series name and in the lower margin at the center
Where is the edition number of a map found?
The upper margin and in the lower left margin, It represents the age of the map- the higher the number the more recent the edition of the map. the initials, or the abbreviation after the edition number indicates who made the map
Where are the bar scales of a map located?
In the center of the lower margin
What is a bar scale?
A ruler used to convert map distance to ground distance
What are the usual three units of measure in a bar scale?
They are eters, statute miles, nautical miles
Where is the contour interval note found?
Usually below the bar scales in the middle of the lower margin
Where is the legend of a map found?
in the lower left margin
What is a contour interval?
The vertical distance of the space between the contour lines. In more recent maps that distance or space is given in meters instead of feet
What is in a map legend?
the symbols that represent topographic features. the symbols are not always the same
how many colors does a map usually have?
five
What are the colors on a map?
black, blue, green , brown, red (reddish brown if the map is readable by red light)
What does the color black represent on a map?
man-made features like buildings and roads
what does the color blue represent on a map?
water features, like lakes, swamps, rivers and drainage
what does the color green represent on a map?
vegetation with military significance such as woods, orchards, or vineyards
what does the color brown represent on a map?
all relief features and elevation, as well as contour lines on older maps
what is longitude?
a measure of distance east or west of the prime meridian
in what city is the prime meridian?
Greenwhich, England
in which direction are the lines of longitude drawn on a map?
North and South
lines of longitude are also known as what?
Meridians
how close will you get to a location with an 8 digit grid coordinate
within 10 meters
What information is used to make a map useful?
marginal data (information in the margins)
What is the difference between an aerial photograph and a photomap?
a photomap is a reproduction of an aerial photograph on which grid lines, marginal data, place names, and other important data have been added-much like a topographic map
what is a map overlay and what is on it?
a sheet of clear plastic or transparent paper with information plotted on it at the same scale as the map or ariel photograph
what is a map overlay used for?
shows current information about friendly and enemy troop positions as well as any other pertinent data a leader may need to know about a certain area. for instance-land mines, communication lines, obstacles
what is latitude
the measure of distance north or south of the equator
what is the starting point for latitude?
the equator
lines of latitude are also known as what?
parallels, because they run parallel to the equator
what type of map system does the u.s military use
The universal Transverse Mercator (UTM) grid
What portion of the world is a UTM map designed for?
That part of the world between lat 84 degrees north and lat 80 degrees south
What is a basic rule for finding coordinates on a map?
Beginning from the left handed-corner, read right and up
what is an azimuth?
it is a direction-a horizontal angle which is measured in degrees or mils from the North
what is a back azimuth?
an azimuth that is 180 degrees in reverse of a given azimuth
how is a back azimuth found?
if the given azimuth is 180 degrees or less- add 180 degrees. if the azimuth is 180 degrees or more-subtract 180 degrees
what is resection?
finding your unknown position by using the back azimuth of two known points. draw lines from the known points. where they intersect is your location. remember to convert all magnetic azimuths to grid azimuths
name 3 types of contour lines
index, intermediate and supplementary
where do intermediate contour lines fall?
they fall between the index lines, are finer and not numered
describe supplementary lines
resemble dashes, they show sudden changes in elevation of at least half the contour interval
how is water flow determined on a map?
contour lines will form a “v” which point upstream
How are valleys and draws shown on a map?
by “u” or “v” shaped contour lines
How does an index contour line differ from other types of contour lines?
index lines are heavier, have an elevation number at some point along the line, and occur every 5th line
what is intersection?
finding an unknown point by shooting an azimuth to it from two known points. the location is where the lines of azimuth intersect. remember to convert the magnetic azimuths to grid azimuths
name the five major terrain features of a map?
hill, ridge, valley, saddle, depression
what are the minor terrain features?
draw, spur, cliff, cut and fill
what branch of the army uses mils?
the artillery
an artillery compass is also known as what type of compass?
an M-2 compass
how many degrees on a compass?
360
name some types of compasses?
lensatic, artillery, wrist/pocket and protractor
what are the two most common compasses used by the army?
the lensatic and artillery compasses
how many scales are on the lensatic compass?
two. one scale is in degrees and the other in mils
how many mils are on a compass?
6400
name the three parts of a compass?
the three main parts are the base,cover, lens. Also there is a sighting wire, graduated straight edge, bezel ring, floating dial, thumb loop, rear sight (lens), sighting loop, luminous magnetic arrow, short luminous line, fixed black index line, luminous sighting dots
what is the bezel ring and how is it used?
it is a ratchet device that clicks when turned. It will click 120 times when fully rotated, and each click is equal to 3 degrees!
why does a bezel click?
it was designed as an aid to determine degrees during nighttime use
what is a bench mark?
a surveyors sign which indicates elevation
what are the two methods for holding a compass?
the centerfold technique and the compass to cheek technique
what affects the performance of a compass?
metal objects and sources of electricity
name two characteristics of a lensatic compass that allow it to be used at night?
the luminous sighting dots, luminous magnetic arrow, short luminous line, the click of the bezel ring, and a luminous E and W
define magnetic declination?
the variation of the true North from The magnetic North. the declination diagram at the bottom margin of the map
how would you hold a lensatic compass?
level and firm -away from any electricity or metal objects such as weapons
describe the fastest way to orient a map?
place a compass on a map and align it with the grid lines insuring that the compass needle points north
how would you orient a map without a compass?
by aligning it with the observable terrain features
name the quadrants of a map
northeast, northwest, southeast, southwest
what three elements are necessary for dead reckoning in land navigation
known starting point, known distance and known azimuth
what is a “flot”?
that is the abbreviation for “forward line of own troops.”
what colors are used in a map overlay, and what do they mean?
black= boundaries blue= friendly forces red= enemy forces yellow= contaminated are, friendly or enemy green= engineer obstacles, friendly or enemy
when colors are not used what symbol is used for enemy forces?
double lines
what size unit is indicated by three dots?
a platoon or detachment
