VIEWS: 15 PAGES: 34 POSTED ON: 12/5/2011
Topographic Maps, Compasses, UTMs 360º make a circle (earth is divided into 360º) Degrees are divided up into 60 smaller units called: MINUTES. Each minute is spilt into 60 parts called: SECONDS. NASA Image To precisely locate points on the earth, degrees latitude and longitude have been divided into minutes and seconds (e.g., Lat:38º53’23”N; Long:77º00’27”W U.S. Capitol Lat: 46° 52' 19.7" N, Long: 113° 59' 38.4" W Missoula, MT) Parallels Meridians Microsoft Missoula, MT Lat: 46° 52' 19.7" N, Long: 113° 59' 38.4" W Great…but what about the realities of declination? Magnetic declination = the difference between true north (the geographic North Pole) and magnetic north (the north that your compass points to). True North Pole (star symbol) The geographic North Pole; the axis around which earth rotates Magnetic North Pole (MN) The north that your compass points to Grid North (GN) The direction of reference lines shown on the map Magnetic declination = the ANGLE between True North and Magnetic North. * The amount of declination at any given point depends on the location of that point on the continent. •Where true and magnetic north are in the same direction, the declination is ZERO. * In North America, a line of zero declination runs from just west of Hudson Bay, down along Lake Michigan, to the Gulf Coast in western Florida. At any point EAST of that zero line, a compass needle will point west of True North (called “westerly declination); in North America, magnetic declination varies from 30° east in AK to 30° west in Labrador. Missoula’s current Magnetic declination: 14° 13' EAST (positive) For online declination adjustments: http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp A compass consists of a magnetized pointer that aligns itself accurately with Earth's magnetic field. A compass provides a known reference direction which is of great assistance in navigation. The cardinal points are north (0°), south (180°), east (90°), and west (270°). The composition of the earth acts as a bar magnet sitting upside down in the middle of the planet. Since its South end is at the north pole and its North end is at the south pole, the North end of a compass needle is pulled north. PACE = 1 natural step FORMULA: PACE = # of meters or feet / # of steps (e.g., 100 feet/25 steps = 4 feet per step) Wright Brothers Scale = the relationship between distance on the map and distance on the ground. Large scale maps Cover large areas 1:500,000 1 inch = 8 miles 1:250,000 1 inch = 4 miles Small scale maps Show details, smaller areas 1:24,000 1 inch = 2,000 feet 1 inch on map = 24k inches in the real world Most USGS topographic maps use brown contours to show the shape and elevation of the terrain. Contour intervals vary, depending on the terrain and the scale of the map. National Parks Digital Guide Tour (Maptech) This grid layout has roots in horseback survey… Union Peak Quadrangle, T13N R14W , NW Section 33 7.5 Minute Series, Revised 1965 (Declination 19 1/2°) John Wesley Powell 1869 Explored the Grand Canyon 1881-1884 U.S. Geological Survey Director The People of the American West met John Wesley Powell’s expeditions across the American West; Powell insisted on an initial survey before entry into the West (beyond the 100th meridian), which inadvertently suspended things like the Homestead Act of 1862. Photo courtesy of the Smithsonian Institution; students of Powell on 1868 expedition; painting Down the Colorado by N. Eggenhofer (1960). Public lands of the western U.S. were surveyed & divided into townships and ranges, according to the U.S. Rectangular System. Similar to latitude and longitude, townships and ranges measure a land area from north to south (township) and east to west (range). Township T2S R3W lies in the 2nd township south of a particular baseline & the 3nd range west of a particular principal meridian. Standard township: 6 miles square Range Township divided into 36 sections of 1 square mile each (640 acres) Township of 36 sections, each 1 square mile (640 acres) Standard township: 6 miles square Early surveyors established section corners & numbered sections The U.S. Geological and Geophysical Survey of the Territories, 1871, National Archives & Records Administration Find the tiny red cross/plus sign on this topographic map. It refers to a section corner marker and the elevation at that particular location. Sometimes corner markers consist of a poured concrete monument with a brass cap; and sometimes they consist of a wood post in a pile of rock (e.g., areas not surveyed since the early 20th century). NW Missoula Quadrangle, Revised 1999 Also, keep an eye out for benchmarks (references points used in surveying, with known locations and elevations). These are often noted on topographic maps with a black “X.” You should be able to locate them on the ground by searching for a brass cap with an elevation number (e.g., “2296” which denotes 2296 ft amsl) Mauna Kea Benchmark, HI; CSUS Archives How do we get more precise than a 640-acre section for our site forms? T40N, R8W Section 7 SE ¼ of the SE ¼ of the SE (SE SE SE) NW NE SW SE UTM (Universal Transverse Mercator) The earth is divided into 60 Zones. Each zone is 6° wide. Each zone is numbered beginning at the 180° meridian near the International Date Line. Each zone divided into 1000-meter (1 km) units. Tick marks along the side of 7.5. minute topo maps represent 1 km within those 1000-m units Any point in a zone can be referenced by citing: 1. its zone number; 2. its distance in meters from Zone 11 Zone 12 the equator (northing); and 3. its distance in meters from a N-S reference line (easting) in each zone; that line is the meridian/longitude line bisecting each UTM zone. 114° longitude NAD 27? NAD 83? The North American Datum = official datum used for the primary geodetic network in North America. In the fields of cartography and land-use there are currently two North American Datums in use: the North American Datum of 1927 (NAD27) and the North American Datum of 1983 (NAD83). Both are geodetic reference systems, but each is based on different measurements. While most USGS topographic maps use the 1927 North American Datum (NAD 27), maps are being slowly revised to NAD 83. Because Earth deviates significantly from a perfect ellipsoid, the ellipsoid that best approximates its shape varies region by region across the world. NAD NAD 1927 is based on the 1927 best suited North America as a whole. Likewise, Clarke Ellipsoid of 1866; it historically most regions of the world used ellipsoids was created by manual measured locally to best suit the earth's shape those regions. surveying of the entire continent. The geodetic As satellite geodesy and remote sensing technology "center" of NAD27 is a base reached high precision and were made available for civilian applications, it became feasible to station at Meades Ranch acquire information referred to a single global in Kansas. ellipsoid. This is because satellites naturally deal with Earth as a monolithic body. Therefore the GRS 80 ellipsoid was developed for best approximating the earth as a whole, and it became the foundation for the North American Datum of 1983. Though generally GRS 80 and its close relative WGS 84 are not the best fit for any given region, a need for the closest fit largely evaporates when a global survey is combined with computers, databases, and software able to compensate for local conditions… DATUM = a fixed reference point which measurements are taken. NAD 27 base station at Meades Ranch in Kansas. located at 39°13′26.71218″N 98°32′31.74604″W / 39.2240867167°N Geodetic = scientific discipline that deals with the measurement and 98.5421516778°W39.2240867167; - / representation of the Earth, including its gravitational field, in a three-dimensional time- 98.5421516778 (39.224087, -98.542152, NAD83). varying space National Register Bulletin 28: Using the UTM Grid System to Record Historic Sites http://www.nps.gov/nr/publications/bulletins/nrb28/ 1. Draw a line from the top of the topo to the bottom, connecting UTM tick marks immediately to the west of the point. 2. Draw a line from the left to the right, connecting UTM ticks marks immediately to the south of the point. 3. Align the counter so that the side of the scale that reads from right to left lies along the east-west line and the side that reads from left to right passes thru the point. 4. Read the coordinate counter scale: right to left for easting & up for northing. NOTE: easting values increase going east; northing values increase going north 4772 (4,771,000) 4770 (4,770,000) 303 (303,000) 305 What if a site spans more than 10 acres? Garnet Ghost Town, c. 1860s-1912 (1940s), Monte Dolack 2004 Label points clockwise starting from NE point REDUCE extraneous area around complex site boundaries The UTM references for Garnet are: Zone 12 A 322405m E, 5187765m N; B 321000m E, 5187771m N; C 321702m E, 51886650m N; D 322425m E, 5188605m N. The legals are: E3/4 of Section 3 and the W1/4 of Section 2 There’s always GPS… “No matter what discovery or sampling techniques are used, the spatial location of the archaeological remains must be RECORDED… …discovery and geographical location are the essential aspects of reconnaissance” (Sharer and Ashmore 2003:242)
"Lecture 02 Topo Maps UTMs Compass"