If you had a globe made of paper, you could carefully try to ‘peel’ it into a flat piece of paper, but you would have a big mess on your hands. 1. We use developable surfaces because they eliminate tearing, although they will produce shearing and compression. Projections must distort features on the surface of the globe during the process of making them flat because projection involves shearing, tearing, and compression. Madison, Wisconsin: JP Publications. The reduction of an area
This topographic map has an RF of 1:24,000, which means that one unit on the map represents 24,000 units on the ground. Gall-Peters projection. Balancing extent and resolution is often one of the most important and difficult decisions a cartographer must make. 3. For example, with the Mercator projection, the shapes of coastlines are accurate on all parts of the map, but countries near the poles appear much larger relative to countries near the equator than they actually are. Many projections are interesting and beautiful, like this Stabius-Werner Projection, but are not intended for navigation between places or to visualize data. Divide it in to 6 equal parts. Bookmark Like 2 Dislike 0 ⚐ Report. If no distortion had occurred in projecting a map, all of the ellipses would be the same size and circular in shape. 1:60,000. Converting Between Scale Types of Historic and Modern Maps, page 3 Converting Representative Fraction (RF)/Ratio Scale to Lexical Scale English and Metric Measures of Length to use:. Verbal description. Many maps state the nominal scale and may even display a bar scale (sometimes merely called a 'scale') to represent it. The geographic coordinate system is designed specifically to define positions on the Earth’s roughly-spherical surface. Find the RF scale for the following graphic scale: By measuring with a ruler (your results may differ depending on screen resolution and size! A measure of strength frequently used in Europe is the reserve factor (RF). . It is always equal to 1 The denominator represents ground distance in the same units as the numerator. A good quality map should have both the RF and Bar Scales. If you had a clear globe the size of a beach ball and placed a light inside this globe, it would cast shadows onto a surrounding surface. In the figure, the origin (0,0) is located at the center of the grid (the intersection of the two bold lines). Full scale: Some times the actual dimensions of the object will be adopted on the drawing then in that case it is represented by the scale and RF as Scale: - 1cm = 1cm or 1:1 and by R.F=1/1 (equal to one). Map Use: Reading, Analysis, and Interpretation,
2. Muehrcke, Phillip C. 1986. This is the scale that you should use when asked to measure distances on the map. The numerator, which is always set to one (i.e., 1), denotes map distance and the denominator denotes ground or “real-world” distance. Reducing a 1:30,00 scale map to 50% of its orginial size changes the RF scale to
In other words, they do not preserve shape, area, or distance, but instead try to avoid extreme distortion. equals 1 million cm. The roles of RF attenuators, terminations, matching pads and loads are important in radio communications test and measurement, as well as in equipment interconnection. Enlarging a map by 200% means to make the enlarged map two times bigger than the original
As we can see with an equal-area projection, however, the ellipses maintain the correct proportions in the sizes of areas on the globe but that their shapes are distorted. A large scale map shows limited distance, but is able to show more detail. Some projections, including the Robinson projection, strike a balance between the different map properties. A printed line that has markings on it that are similar to those on a ruler. A map can have a representative fraction, graphic scale, or verbal description that all mean the same thing. You must have seen maps with a scale bar indicating equal divisions, each marked with readings in kilometres or miles. The extent of the map is national while the resolution is at the state level because they are the finest level of spatial detail that we can see. Data from SocialExplorer and US Census. Of these three problems, tearing is seen as the worst because you would be making maps with all sorts of holes in them! The point at which both x and y equal zero is called the origin of the coordinate system. . The Nature of Geographic Information: An Open Geospatial Textbook. Eric Gab Data: U.S. NGDC World Coast Line (public domain), GFDL. Or it is also called Scale factor. Graphic Scale to RF. How many miles to the inch when the RF = 1:24,000? • Divide the first part A0 into 10 equal … The top image has a spatial resolution of the county and the bottom has a spatial resolution of census tracts. . The relationship between ground and map distance can be expressed by either a linear or
Economies of scale can be both internal and external. when the RF = 24,000? Safe Living Technologies Inc. has created a RF unit conversion table and EMF unit conversion table: For Code A and B 3 Guidelines for evaluation of section ‘B’ 1. The term “map projection” refers to both the process and product of transforming spatial coordinates on a three-dimensional sphere to a two-dimensional plane. For example, it is common to see “one inch represents one kilometer” or something similar written on a map to give map users an idea of the scale of the map. How many km to the cm. Instead of the two linear measurement scales x and y, as with a Cartesian grid, the geographic coordinate system uses an east-west scale, called longitude that ranges from +180° to -180°. Scale descriptions using the RF provide one way of considering scale, since 1:1000 is larger than 1:1,000,000. For example, if we say that the scale of a map is 1 cm : 1 km, it would be understood by only that person who is familiar with the metric system of measurement. Compromise projections preserve no one property but instead seek a compromise that minimizes distortion of all kinds, as with the Robinson projection, which is often used for small-scale thematic maps of the world. . When we visually represent a region of the world on a map, we must reduce its size to fit within the boundaries of the map. "The larger the number, the smaller the scale" sounds confusing, but it is easy to understand. Indiana, Pennsylvania: National Council for Geographic Education. Shearing, tearing, compression. Graphic Scale to RF. . The flat surface touches the globe and it is the point on the projected map which has the least distortion. Log in. from map units to ground units. A conformal projection will have distortion ellipses that vary substantially in size, but are all the same circular shape. The fraction 1/100 is a much much smaller number than is 1/2. This map shows a national extent and a state resolution. When a map is enlarged or reduced, the bar scale changes size in direct proportion to the map. second edition. ∠oa ∠PA 60000' 1' 60000' 12" = = = H f s Scale of a Vertical Aerial Photograph Over Variable Terrain h is the measurement of the elevation of a point above the sea level and the H is the altitude above sea level. 3. Map scales. Note how the shape of Greenland is significantly altered, but the size of its area is correct in comparison to other regions such as Africa. If either group of 3 balls is heavier, take 2 balls from the heavier side. Adapted from Anthony C. Robinson. The projection was developed in 1923 by John Paul Goode to provide an alternative to the Mercator projection for portraying global areal relationships. The Mercator projection is conformal because it preserves shape and angle but strongly distorts area. For example, if the scale is 10 m to 1 cm, the RF of the scale is 1cm/10x100cm = 1/1000. Some maps, especially older ones, use a verbal description of scale. case 2. This is a bit misleading because no projection can maintain relative distance between all places on the map. The properties we will focus on are shape, area, and distance. CC BY-NC-SA 4.0. (2012) Mapping our Changing World. The figure has scale bars for 1 mile, 7000 feet, and 1 kilometer. Areal measurement most often is
In reality, it is more of an ellipsoid with a few bulges, but it is fine to think of it as a sphere. In this chapter, we have explored the concepts of scale, resolution, and projection. The Language of Maps, Pathway in Geography series. New York: Macmillian Publishing Company. to twenty thousand". CC BY-NC-ND 3.0. Robinson Projection. Adapted from Sutton, O. Dassau, M. Sutton (2009). The fraction 1/100 is a much much smaller number than is 1/2. Projection is the process of making a two-dimensional map from a three-dimensional globe. Learn vocabulary, terms, and more with flashcards, games, and other study tools. 1. R. F. is representation factor. Lines of longitude are not parallel, but converge toward the poles. The world is vast. Equidistant maps are able, however, to preserve distances along a few clearly specified lines. It can be expressed as 1/100,000 or 1:100,000. Equal-area projections are preferred for small-scale thematic mapping, especially when map users are expected to compare sizes of area features like countries and continents. To draw a scale, need to know the “Representative Factor (RF)”. These divisions are used to find out the ground distance on the map. the place where the developable surface touches the globe is known as the tangent point or tangent line. Scale Comparisons Consider the size of the fractions 1/100 and 1/2. Mercator projection. Show a distance of 4.56 meters • Length of the scale = (3/200) x 6 m = 9 cm • Draw a line AB = 9 cm . The poles all points are the proportionally correct distance and direction from the center point not as as. Light bulb, and projection shapes and angles measured on the surface of the earth dots mark tangent! ) earth into a two-dimensional map from a United States Geological Survey ( USGS ) topographic map Information systems CC! 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