GC 225 Lecture Exam #2

Direction- path along which something is moving.

3 Types;

- COMPASS DIRECTIONAL NAME (32 in total)

- BEARING (four 0o - 90

o)

- AZIMUTHS (0o - 360

o)

Baselines – typically north – south trending lines;

- True North - Northerly direction along a line of longitude.

- Magnetic North - Direction to the magnetic north pole of the earth.

- Grid North - North trending direction aligned to specialized grid lines on the maps.

Magnetic Declination – angular difference between true north and magnetic north in a location.

AGONIC LINE - an imaginary

line on the earth's surface along

which true north and magnetic

north are identical.

S

NCompass (32 named points)

0

90

NE

SE

Bearings (4 quadrants)

NW

SW

0

90

S ____ E

N ___ EN ___ W

S ___ E

0

90

180

45

135225

315

Azimuth 0-3600

270

Agonic Line

Magnetic North

MAP ORIENTATION

1.) INSPECTION – looking for easily recognizable landmarks.

2.) RESECTION – sighting on known ground positions.

3.) INTERSECTION – object with unknown position.

Route Selection – planning the best route (path) from A to B using a map.

GPS (GLOBAL POSITIONING SYSTEM)

1.) Space Segment - cluster of 24 satellites, orbiting in 6 planes (4 in each plane).

2.) Control Segment – operates GPS in master stations close to the equator. (Colorado)

3.) User Segment – small hand-held receiver unit.

(Need 3 satellites to determine exact position, more the better)

Spot Heights – a known height of a point relative to a datum (sea level)

(Exm. = Lake Superior 602 feet above sea level)

Map

Your position on map

RESECTION

Unknown Position

Map

INTERSECTION

Position is Known

1

2

3

13 KnownPositions

Object with unknown position

2

Contours – imaginary lines that join points of equal elevation relative to a datum (sea level).

- CONTOUR INTERVAL - vertical distance between contours.

Types;

– Index (darker, every 5th line, often labeled)

– Intermediate (lighter)

– Supplementary (extra lines at half intervals)

– Depression (have ticks and are read downward)

– Approximate (dashed or dotted)

– Carrying (very close, indicates drastic slope)

OTHER WAYS OF SHOWING RELIEF

• Layer Tints

– Colors or grey tones used to fill in between contours.

• Illuminated Contours

– Adds artificial brightness and shading to contours to further accentuate

topography.

• Hill Shading

– Similar to above but with no contours.

• Physical Model

– Three dimensional model is made of plastic, etc.

• Block Diagrams (Armin K. Lobeck)

– Three-dimensional representation of landscape and below ground features.

CONTOUR INTERPRETATION

- Contours always close

- Closed contours = hill or depression

- Variations in horizontal spacing of contours reflect variations in slope.

Close = steep Wide = flat (general)

- Contours crossing valleys ‘point’ upsteam

- INTERFLUVES - Contours with ‘closed ends’ indicate ridges of drainage divides.

CONTOUR APPLICATIONS

- LINEAR INTERPOLATION – point between contour lines, may be used to estimate.

- PROFILING – a simple cross-section view through a particular piece of terrain.

- SLOPE – a measure of the vertical difference in elevation of a surface at 2 different

points in relation to the horizontal distance between same points. (rise over run)

CLOSED DEPRESSIONS

Causes;

- Wind Erosion (deflation)

- Glacial Activity (Kettle Lakes)

- Impact Craters (Meteorites)

- Karst Processes (Sink Holes)

- Human Activity (Mining, Quarrying)

STREAM & DRAINAGE PATTERNS

10 mm

Z 6 mm

Delta – landforms with flat surface that may form where a creek/river enters a large body of

water. May have many shapes and outlines (birds foot).

Alluvial Fan - Landform that is fan shaped that forms where a river, stream, or creek leaves its

valley and enters a larger valley or basin. Common in arid, semi-arid settings and with areas of a

great deal of runoff such as construction sites.

COASTAL LANDFORMS

Erosional – wave cut (bluffs, cliffs, terraces)

Depositional – spits, barriers, tambolos, beach ridges

TOMBOLO – land locked island.

(Presque Isle)

LAGOON – closed in water by a Bay Barrier.

(Big Bay / Lake Independence)

BEACH RIDGES – old beach locations

which are now above lake/sea level.

(Alger County)

SPIT – small peninsula sticking out making

a point. (Little Presque)

GLACIAL LANDFORMS

• Alpine (Mountain) Glacial Landforms

U-Shaped Valleys (Troughs)

Arêtes – knife shaped feature.

Horns – mountain top, created by a collection of Arêtes.

Cols – lowest dip between mountains.

Cirques – mountain 3-sided valley, where glaciers are or used to be.

Tarns – depression that has filled up with water.

• Continental Glacial Landforms

– Moraines – unsorted gravel/debris made by a glacier front.

– Outwash plains – flat area, where glaciers stalled and dumped water/sand.

– Kettle Lakes – lakes are formed from depressions & a reseeding glacier.

– Drumlins – teardrop shape, stuck up under a glacier, causing debris to collect.

– Eskers – an inverted valley, ahead of the old glacier.

– Roche Moutonnées – causing one side to be rock & the other dirt.

Eolian Features – windblown or degraded features.

Cuestas – step slopes on a rock ledge.

Transverse Dunes Barcain Dunes