Topographic Maps. Review

Topographic Maps Review

Topographic Maps Types of Topographic Maps 1:24,000-7.5 minute maps 1:50,000-15 minute maps 1:100,000 maps 30x60 minute maps 1:250,000 maps 1 o x 2 o degree maps 1:500,000 maps State Maps/Tactical Pilotage Chart 1:1,000,000 maps Operational Navigational Chart 1:2,000,000 maps Jet Navigational Chart 1:5,000,000 maps Global Navigation/Planning Chart

Topographic Maps 1:24,000-7.5 minute maps 1:50,000-15 minute maps

Topographic Maps Elements on Topographic Maps Can aid in interpreting maps. Elements can tell you the map Type Quadrant Coordinate system Location Boundary Measurement Features

Title Title Elements of Topographic Maps All Topographic maps have a TITLE. The TITLE is usually found in the top right hand corner on USGS 1:24,000 Maps.

Title Elements of Topographic Maps At times the Title is found in the middle of the map. Example - 1:50,000 scale maps and smaller will have titles in the middle of the map. Title

The 1:24,000 USGS maps typically place MAP TYPE below the title. named after the most prominent feature in the quadrangle. must know map type to work at most appropriate scale. Map Type

The MAP TYPE can be determined by: subtracting corner latitudes or longitudes Example: Subtract Lat. or Long. minutes at corners of map to come up with map type: 30 15 = 15 15 minute quadrangle map

All topographic maps have a coordinate system. May have more than one grid system Latitude and Longitude can be expressed in degrees, minutes & seconds, minutes & seconds or just minutes

All topographic maps have a coordinate system. May have more than one grid system. UTM is expressed in meters. Universal Transverse Mercator

Where to find COORDINATE SYSTEM values Longitude is found at top and bottom corners, and along top and bottom Longitude of map. Latitude is found on corners and along the sides of a map. Units in degreesminutes-seconds. Latitude Universal Transverse Mercator found along sides of map, units expressed in meters. 3 35 = 335,000 meters 34 85 = 3,485,000 meters

Locating Lat/Long or UTM Values Black tic marks associated with Lat/Long Blue tic marks associated with UTM

All topographic maps have a Tic Mark. Intersecting Tic Marks define the corners of a Latitude/Longitude Grid. Tic Mark

How to read UTM values Universe Transverse Mercator The number 34 79 is read as 3479000 meters

Regardless of map scale, all numbered black UTM Grid Lines are 1,000 meters apart. 1,000 meters 1,000 meters

All topographic maps have contour lines. Contour lines depict elevation above sea level Regular Contour Line 420 Contour Interval the difference in elevation between Contour lines. Index Contour Lines

The Legend is one of the most important features on a topographic map.

Colors The colors on a topographic map are symbolic of different map features. Blue = water Green = forest Brown = contour lines Black = cultural features (buildings, place names, boundary lines, roads, etc.) Red = principal roads Salmon shading = urban areas Purple shading = revisions to an older map, compiled from aerial photos. If an area has become urbanized, this may be shown as purple shading on the new, revised map.

USGS 1:24,000 maps will often illustrate map location by the use of a locator or index map.

USGS 1:24,0000 maps describe adjacent quadrangles by labeling the adjacent quad on the map. Adjacent quad labels are described in 3 places Map Corners, Middle of Map, and Sides of the Map. Index Number and Quad Name

Scale shows the relationship between the distance on the map and the distance on the ground. Representative fraction Bar scale Meaningful verbal scale

The Contour Interval is displayed below the scale bar. It defines the distance between contour lines. The Datum is also specified.

North Orientation Topo maps show 3 different kinds of north orientation arrows. True North True North Grid North Magnetic North Grid North Magnetic North

True North Orientation True North True North refers to the direction of the North Pole.

Grid North Orientation Grid North refers to direction northwards along the grid lines of a map projection or coordinate system. Grid North

Grid North Orientation North or 360 0 on a protractor indicates Grid North. Grid North

Magnetic Northis the wandering point on the Earth's surface at which the Earth's magnetic field points vertically downwards (i.e. the "dip" is 90 ). Magnetic North

Magnetic Declinationshows the difference between true north and magnetic north. Magnetic North

Topo maps also contain additional information Such as, who made the map?

Conclusion Knowing the basic elements of a Topographic map can aid you in determining- coordinates in both UTM and Latitude and Longitude grid systems. which topographic maps are adjacent to the one you are reading. scale for determining distance and area. elevation. direction the difference between Grid, Magnetic, and True North.

Conversion between Degrees Minutes and Seconds and Decimal Degrees From Decimal Degrees to Degrees Minutes and Seconds The whole units of degrees will remain the same (i.e. in 121.135 longitude, start with 121 ). Multiply the decimal by 60 (i.e..135 * 60 = 8.1). The whole number becomes the minutes (8'). Take the remaining decimal and multiply by 60. (i.e..1 * 60 = 6). The resulting number becomes the seconds (6"). Seconds can remain as a decimal. Take your three sets of numbers and put them together, using the symbols for degrees ( ), minutes ( ), and seconds (") (i.e. 121 8'6" longitude)

Conversion between Degrees Minutes and Seconds and Decimal Degrees From Degrees Minutes and Seconds to Decimal Degrees The whole units of degrees will remain the same (i.e. in 121 8'6" longitude, start with 121 ). Divide the Minutes by 60 (i.e. 8 / 60 = 0.133333). Divide the Seconds by 3600( i.e. 6 / 3600 = 0.00166667 ). Add the above three numbers 121 + 0.13333333 + 0.0016667 = 121.13499999997