GC 225 Lecture Exam #2

Transcription

1 GC 225 Lecture Exam #2 Direction- path along which something is moving. 3 Types; - COMPASS DIRECTIONAL NAME (32 in total) - BEARING (four 0 o - 90 o ) - AZIMUTHS (0 o o ) Compass (32 named points) N N W Bearings (4 quadrants) 0 N E Azimuth NW NE S S E SW 0 SE S E 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. Magnetic North Agonic Line

2 MAP ORIENTATION 1.) INSPECTION looking for easily recognizable landmarks. 2.) RESECTION sighting on known ground positions. 3.) INTERSECTION object with unknown position. RESECTION INTERSECTION 3 Known Positions 2 1 Position is Known Unknown Position Map Your position on map Object with unknown position Map 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)

3 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) Layer Tints OTHER WAYS OF SHOWING RELIEF 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.

4 CONTOUR APPLICATIONS - LINEAR INTERPOLATION point between contour lines, may be used to estimate. Z 6 mm 10 mm - 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

5 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) Alpine (Mountain) Glacial Landforms U-Shaped Valleys (Troughs) Arêtes knife shaped feature. GLACIAL LANDFORMS 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.

6 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