QUESTIONS FOR QUIZ G: GEOG 360 From Cartography: Thematic Map Design: How did Eratosthenes calculate the circumference of the earth ? He observes that on the summer solstice the sun shone directly down to the ground in Syene, but the sun is not directly overhead in Alexandria. There is 7;12’(which is 1/50 of a full circle) difference between these two cities. Then he estimated the distance between Alexandria and Syene. Multiply the distance by 50, he estimate was 250000 stadia. What is a Geoid ? It means earth-shaped. What ellipsoid is used by the North American Datum of 1983 (NAD83) ? Geodetic Reference System 1980 (GRS80) ellipsoid. How many degrees are in the sexagesimal scale ? 360 degrees . What is a ‘Great Circle’ ? When earth is bisect into two halves, it is referred as Great Circle. What is a ‘Loxodrome’ ? This is a line on the map which has a constant compass bearing. What is the equation for finding map scale ? Map scale = (map distance)/(earth Distance) What are the three types of distortion created during the projection process ? Deformation of graticule Relative size and shape of continent and ocean. Distance and direction. What is Tissot’s Indicatrix ? It is a way that can show the distortion at points on the projection graticule. What is a ‘standard line’ on a projection ? Lines in tangency or intersection on the map are called standard line. What are the three ‘families’ of projections ? Azimuthal Family Cylindrical Family Conic Family. From Mapping: Ways of Representing the World : What does the author suggest is wrong with ‘the rectangular representation of the earth’ ?
- Spring '08
- Cartography, Map projection