Nav 07 - 09 - Map Projections Flashcards
Review Questions
What is the definition of Latitude?
Angular distance from the equator measured along a Meridian
Review Questions
What is the definition of Longitude
A semi-Great Circle of the surface of the Earth joining the poles of the earth
What is a map?
A small scale, flat surface representation of some portion of the earth’s surface
Define Conformality
The correct representation of angles
For a map to be conformal, what must be met?
Meridians and parallels must intercept at right angles
Scale must be the same in all directions or change at a constant rate
Define Orthomorphism
Shapes are correctly defined
To possess correct shape, a map must be:
Conformal
Scale must be the same in all directions
True or false
It is difficult to keep the scale constant over an entire surface, but it can be considered correct over small areas.
False, it is impossible to keep the scale constant over an entire surface
Define Scale
A ratio of given distance on a map to the actual distance on the earth
What are the methods of expressing scale?
Representative fraction
Statement in words
Graduated scale
A 1 : 500 000 map is what size of scale, show what size of area, and show more of what compared to a 1 : 1 000 000 map?
A 1 : 500 000 map is a large scale, shows a smaller area and more detail than a 1 : 1 000 000 map, which show a larger area with less detail.
The three types of map projections in general use are?
Cylindrical
Conical
Azimuthal / Tangential
A Mercator projection is derived from what map projection?
Cylindrical
On a Mercator projection, a Rhumb line and a Great circle are illustrated how?
A Rhumb line is straight, a Great circle is curved and convex towards nearer pole.
Describe the following Mercator Projection properties.
Parallels Meridians Scale Shapes Great Circle Rhumb Line
Parallels: Straight lines, unequally spaced
Meridians: Straight lines, parallel, equally spaced
Scale: Correct at equator, expands away from equator
Shapes: Preserved (approx) near equator, but distorts increasingly away from equator.
Great Circle: Curved, convex to nearer pole
Rhumb Line: Straight lines
What are the limitations of the Mercator Projection map?
Excessive scale expansion
Enormous area distortion in higher latitudes
Great Circles are plotted as curved lines
What are the other cylindrical projections (apart from standard cylindrical)?
Transverse Mercator
Oblique Mercator
A Transverse Mercator map is useful for what routes?
North-South routes along a given meridian.
True or false
An Oblique Mercator map is used to show regions along a Great Circle other than the Equator or a particular meridian of longitiude.
True
What type of map is a Oblique Mercator used to create?
A strip map
Points along a strip map retain all the advantages of the Mercator at the ________.
Equator
The line of tangency on a strip map is a straight line and is a (Rhumb line or Great Circle)?
Great Circle
The Lambert Conformal projection is a variation of what projection?
Conical
How many points of tangency does a Lambert Conformal map have?
2 points of tangency
