Topographic Maps Thursday, April 20, 2017

What is a topographic map? A map that shows elevation changes for a specific region.

PURPOSE OF A TOPO MAP A MAP PROVIDES INFORMATION ON THE EXSISTENCE OF, THE LOCATION OF, AND THE DISTANCES BETWEEN GROUND FEATURES. SUCH AS POPULATED PLACES ROUTES OF TRAVEL VARIATIONS IN TERRAIN HEIGHTS OF NATURAL FEATURES THE EXTENTOF VEGETATION COVER.

Contour Lines Contour lines indicate elevation. They are the main part of any topographic map.

Regular Contour Lines Regular contour lines are normally the thin brown lines which dominate a topo map.

Index Contour Lines                                   Are thicker and are labeled with an elevation.

Read Between the Lines! The closer the lines are, the steeper the slope. The further, the more gentle

                                                                                      Gradient

Contour Each of these kids stands upon a different contour line. Yes, it’s imaginary.

Get the Idea? With a regular map, we can get the outline of the island, but have no idea as to elevation change (topography).

All Elevation Below 10 Feet Under Water Notice how the island has shrank a bit.

All Below 20’ Under!

All Below 30’ Under!

That’s The Idea!

Can You Guess The Elevation?

Contour Interval Amount of elevation change between each contour line.

What is the Contour Interval?

Streams

Closer Look: Streams

Plateaus (Summits)

Note: Index, Depression

Note: Pond/Lake

Various Roads/Highways

HILL: AN AREA OF HIGH GROUND. FROM A HILLTOP, THE GROUND SLOPE DOWN IN ALL DIRECTIONS. Contour lines forming concentric circles.

VALLEY: A STRETCHED-OUT GROOVE IN THE LAND, USUALLY FORMED BY STREAMS OR RIVERS. Contour lines form U lines tend to parallel stream before crossing. Contour line crossing streams ALWAYS point up stream. Usually plenty of room to maneuver

RIDGE: A SLOPING LINE OF HIGH GROUND. Contour lines forming a U or V; always point to high ground.

SADDLE: A DIP OR LOW POINT BETWEEN TWO AREAS OF HIGHER GROUND. Between 2 hilltops or a break in the level crest of a ridge. Saddle usually appear as an hourglass

DEPRESSION: A LOW PO INT IN THE GROUND OR SINKHOLE. THEY ARE REPRESENTED BY CLOSE CONTOUR LINES THAT HAVE TICK MARKS POINTING TOWARD LOW GROUND. In a depression there is higher ground on ALL sides

DRAW: A LESS DEVELOPED STEAM COURSE THAN A VALLEY. THERE IS ESSENTIALLY NO LEVEL GROUND AND, THEREFORE, LITTLE OR NO MANEUVER ROOM WITHIN ITS CONFINES. ) Contour lines are V Shaped with the points of the V POINTING UPHILL and UPSTREAM

SPUR: A SHORT, CONTINUOUS SLOPING LINE OF HIGHER GROUND, NORMALLY JUTTING OUT FROM THE SIDE OF A RIDGE. FM 21-26: PAGE 10-12 (FIGURE 10-23) ususally formed by parrallel streams cutting down the side of a ridge Contour lines shaped like U or Vs point AWAY From HIGH GROUND

CLIFF: A VERTICAL OR NEAR VERTICAL FEATURE; IT IS AN ABRUPT CHANGE OF THE LAND. THE SLOPE IS SO STEEP THAT THE CONTOUR LINES CONVERGE INTO ONE CONTOUR LINE OR THE LAST CONTOUR LINE HAS TICK MARKS POINTING TO LOW GROUND.

CUT: A MAN-MADE FEATURE RESULTIING FROM CUTTING THROUGH RAISED GROUND, USUALLY TO FROM A LEVEL BED FOR A ROAD OR RAILROAD TRACK. FILL: A MAN-MADE FEATURE RESULTING FROM FILLING A LOW AREA, USUALLY TO FORM A LEVEL BED FOR A ROAD OR RAIL- ROAD TRACK.