Topic 9 Flashcards

Question

if your map is off mostly likely someone has incorrectly defined the reference system T/F?

Answer 1

true 70m is a small error for canada as a whole erros are inherently built inot the NAD27

Answer 2

NTv2 NADCOW for USA very small difference between the NAD83 and the updated 2010 Alberta model of NAD83

Answer 3

last arc second = aprx. 30 meters long arc second = depends what lat at north pole + = so tiny much larger at equator

Answer 4

cartesian how ti should be drawn on a flat surface drawing a 3d volume on a flat surface distortions will happen (golden triangle problem) choice of projection depends on what you are doing descringly important as cartogprahy scale increases (zoom in) bigger area = projection more important converting to x,y point positions

Answer 5

developable surfaces ("the paper") plane, cone, cyclinder

Answer 6

gnomic projection source at centre of earth used for navigation charts orthographic infinite light source looks like earth from space stereographic light from back or side of globe common historically mapping polar regions lambert conformal basemap for BC (used heaviley in Canada)

Answer 7

tranverse mercator canada = lambert conformal conic

Answer 8

mercator :wrapped around equator transverse mercator : wrapped around poles

Answer 9

shape area distance direction each projection is designed to achieve one or two of these

Answer 10

unit circle on globe visual help in understanding distortions preserve shape = conformal angles are the same size will vary preserve area = equal area area preserved angles compromised

Answer 11

scale is the same in every direction around any given point (isotropic) scale changes between areas of the map shapes for small regions are portrayed accurately cant compare sizes lambert conformal conic

Answer 12

scale in small area changes depending on direction (anisotropic) shapes in small areas are distorted cant compare shape bonne projection albers equal area vs lambert conformal

Answer 13

true distances distance between any point and the north pole is true doesnt work for any two random points tho usualyl azimuthal no map can be conformal and equal area at the same time azimuthal equidistant projection conic equidistant projection

Answer 14

direction measurements on the map same as those on the ground can be conformal, mercator can be maintained simultaneously with one or two of the other 3 properties

Answer 15

stretching: where paper is above the globe c is not distorted a and e are stretched a lot b and d are stretched a little 1 standard line

Answer 16

shrinking: there paper is "inside" the globe b and d are not distorted a and e stretched (paper is above the globe) c is shrunken 2 standard lines

Answer 17

tangent = 1 standard line secant = 2 standard lines

Answer 18

plotting cartesian points on a x,y graph

Answer 19

basis of many topographic maps globe is divided into 60, 6 degree longitudinal strips each strip is "numbered zone" subdivided into latititude strips

Answer 20

cyclindrical conformal projection secant pick meridian 6 degrees of longitude or strips, or zones maps are windows in the zones doesnt go all the way to the polar regions but only 84 degrees north and 80 degrees south central meridian moves with the projection UTM is only unique to a geographic coordinate system standard lines are not actually defined center of meridian = 500,000 m E so that we are always using positive numbers

Answer 21

orderly system of parallels and meridians used to draw a map on a flat surface distortion must occur when transforming information from 3d to a flat surface choice of projection is dependent on the purpose of the map decreasingly important as cartographic scale increases

Answer 22

go by desired properties basic guidelines there is no right answer only good and bad choices trying to match the projection with the shape of the mapped earth plate fixed or ECEF

Topic 9 Flashcards

(47 cards)