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Understanding Map Scales and Scale Types for Accurate Measurements

Learn about different scale types on maps, including verbal, visual, and representative fraction scales. Discover how to determine scale and convert distances accurately. Transform scales from verbal to RF and vice versa for precise measurements.

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Understanding Map Scales and Scale Types for Accurate Measurements

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  1. SCALE

  2. SCALE • size of an object on a map compared to the actual object on the ground • may not be the same in all directions from a point

  3. SCALE TYPES Verbal scale • describes the scale in words; a relationship between a map distance and a ground distance. i.e. “one centimeter represents one kilometer” • commonly found on popular atlases and maps

  4. one end can be divided SCALE TYPES Visual scale(bar scale or graphic scale) • graphically illustrates relationship between map distance and ground distance. • most common • remains correct if reduced or enlarged

  5. SCALE TYPES Visual scale(bar scale or graphic scale)

  6. SCALE TYPES Representative Fraction (RF) • ratio (proportion) between map distance to earth distance i.e. 1:50,000 • most versatile; not tied to any specific units

  7. SCALE TYPES Representative Fraction (RF) • The abstract nature of RF scales confuses many people. They ask, “one what is equal to 24,000 of what?” The key is that you can put in any unit you want instead of “what” in the question. That’s what makes it the most flexible type of scale.

  8. Representative Fraction Globe distanceEarth distance = Map Scale: Map Projection: Scale Factor (e.g. 1:24,000) SCALE FACTOR

  9. SCALE FACTOR • stated scale is correct only at selected points • statement of relation between given scale and actual scale value i.e. SF of 2.000 would mean that actual scale is twice the principal scale

  10. LARGE VS SMALL SCALE • large scale: show a small area with a large amount of detail. • small scale: show a large area with a small amount of detail • all relative

  11. DETERMING SCALE • use map scale to convert map distance to ground distance. • for verbal and RF scales - multiply by the scale, then convert the ground distance to units suitable for ground measurements. i.e. we have a map with a scale of 1:50,000. We measure the distance along a property boundary as 1.7 cm. What is the length in the real world? • for graphic scales – mark off a distance on the map and compare it directly to the bar scale.

  12. TRANSFORMING SCALES Verbal to RF • write verbal scale as a fraction then convert so that both numerator and denominator have the same units and numerator has a 1 i.e. convert verbal scale “1 cm represents 100 km” to RF RF to Verbal i.e. convert from RF of 1:25,000 to verbal scale, in metric

  13. TRANSFORMING SCALES Graphic Scales and RF/Verbal • take the measurement from the bar scale to determine the map distance and corresponding ground distance. i.e. 10 km on ground measures 2.4 cm on map. • use method for verbal scale to RF conversion.

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