What is orthomorphism? What is required for it?
Correct bearings, and therefore shapes are also correct.
Scale about a point must be the same in all directions for a short distance
Meridians and parallels must intersect at 90*
What is conformality?
It is the same as orthomorphism
What is equivalence? What is required for it?
The map is equal area, or at a reduced scale.
Scale cannot be kept constant
Expansion in one scale must be equal and opposite in the other direction
How can a scale be expressed?
Simple statement
Representative fraction
Graphic/ graduated scale
What are the properties of a Mercator? (7)
- Meridians are parallel, evenly spaced straight lines
- Parallels are straight lines that expand away from the equator, intersect at 90*
- Scale correct at the equator, expands as sec(latitude)
- Higher than 70* latitude scale becomes too distorted
- Rhumb line is a straight line
- Great circle is a curve, concave to the equator
- It is orthomorphic
How does scale vary on a conic projection with two standard parallels?
Contracts between them and expands beyond them
What are the properties of a Lambert’s conformal?
- Meridians are straight lines radiating from the pole
- Parallels are concentric arcs that intersect at 90*
- Scale is correct at the 2 standard parallels
- Scale error is small so it can be considered constant on a single sheet
- Great circle is approximated by a straight line and is always closer to the pole
- Rhumb line is a curve, concave to the pole
- The map is conformal
- Adjacent sheets will fit if they have the same standard parallels
What uses does the Lambert conformal have?
Radio navigation
Countries with large East - West extent
What uses does the Mercator have?
Tropical maps
Dead reckoning/ celestial
Countries with large North - South Extent (transverse Mercator)
What is the equation for determining scale?
Scale = Chart Distance/Earth Distance
What are the conversions for different units of measurements
2.54cm = 1in 12in = 1ft 1nm = 6076ft / 1852m 1sm = 5280ft 1km = 3280ft
What requirements should an aviation chart have?
- Orthomorphism (primary)
- Rhumb lines are straight lines
- Distances are measurable
- Adjacent sheets should fit
What requirements does an aviation Map have?
- Shapes shown fairly correctly
- Scale fairly constant and any error distributed evenly
- Adjacent sheets fit
What is the equation for chart convergency?
-CHLONG * Sin(mean Latitude)
