TOPOGRAPHIC MAPS
I
TOPOGRAPHIC MAP- A MAP WHICH
SHOWS ELEVATION WITH THE USE OF
CONTOUR LINES, SHAPES , AND
SYMBOLS
A) CONTOUR LINES- LINES DRAWN TO
CONNECT POINTS OF THE SAME
ELEVATION
II
THREE THINGS CONTOUR LINES
SHOW US
A) ELEVATION
1) CONTOUR INTERVAL- THE DIFFERENCE
IN ELEVATION BETWEEN TWO
CONSECUTIVE CONTOUR LINES
2) INDEX CONTOUR- EVERY FIFTH OR
FOURTH LINE WHICH IS DARKENED FOR
EASY READING
B) STEEPNESS OF SLOPES
1) CLOSER CONTOUR LINES = STEEP SLOPES
2) WELL-SPACED CONTOUR LINES =
FLATTER, GENTLE SLOPES
C)THE SHAPE OF THE LAND AT VARIOUS
HEIGHTS
III
ELEVATIONS OF LAND BELOW SEA
LEVEL ( SINKHOLE, QUARRY, MINE)
A) MEASURED USING A HACHURE LINE
B)
FIRST DEPRESSION LINE TAKES THE
VALUE OF THE CONTOUR LINE
SURROUNDING IT
C)THE “WHISKERS” POINT TO THE LOWER
ELEVATION
IV
INFORMATION LEARNED FROM A
TOPOGRAPHIC MAP
A) A BENCHMARK POINT IS A LOCATION
WHOSE EXACT ELEVATION IS KNOWN
AND IS NOTED ON A BRASS ALLUMINUM
PLATE ( BM )
B) MAXIMUM ELEVATION- HIGHEST
POSSIBLE ELEVATION
1) FIGURE OUT WHAT THE NEXT POSSIBLE
CONTOUR LINE WOULD BE THEN
SUBTRACT 1 UNIT
C)
MINIMUM ELEVATION- LOWEST
POSSIBLE ELEVATION
1) THE NEXT POSSIBLE DEPRESSION LINE,
THEN PLUS ONE UNIT
D) RIVERS CUT A VALLEY AND CREATE A VSHAPE POINTING TO THE SOURCE OF THE
STREAM (UPSTREAM).
E) GRADIENT = CHANGE IN ELEVATION (ft)
DISTANCE (mi)
F) PROFILE- SIDE VIEW OF THE SHAPE OF
THE LAND ON A TOPOGRAPHIC MAP
G) RELIEF- DIFFERENCE IN ELEVATION
H) RELIEF MAP – RAISED MAP WHICH
SHOWS DIFFERENCE IN ELEVATION
(3-D)