Lambert's Conformal Projection Flashcards
(36 cards)
Regarding conic projections, what is chart convergency proportional to?
Parallel of origin.
The higher its latitude, the greater the convergency.
On a Lambert’s conformal conical projection, what determines the usable area?
The usable area usually falls between the two standard parallels.
On a Lambert’s conformal conic chart, what is the latitude range of usable area?
24° (to keep scale errors below 1 %).
How to calculate the parallel of origin from the standard parallels?
Add the standard parallels and divide them by two.
The parallel of origin is assumed to be the average of standard parallels.
How do:
(a) parallels of latitude
(b) meridians of longitude
appear on a Lambert’s conformal conic chart?
(a) arcs of concentric circles around a pole
(b) straight lines converging on the apex
Regarding Lambert’s conformal conical projection, where is the scale correct?
At either standard parallel.
How is the:
(a) internal
(b) external
cone used in Lambert’s conformal conical projections called?
(a) secant cone
(b) tangent cone
Describe the ideal properties of:
(a) convergency
(b) scale
(c) great circle tracks
on Lambert’s conformal conic charts.
Provided that the standard parallels are correctly chosen:
(a) chart convergency = earth convergency
(b) scale is constant
(c) great circles are straight lines
What does the convergence factor equal?
The sine of the parallel of origin.
Regarding Lambert’s conformal conical projection, how does the cone distance vary from the reduced Earth distance?
(a) contracts on the internal cone
(b) expands on the external cone
Define: chart convergency.
The change in great circle bearings between two positions.
On Lambert’s conformal conic charts, how does scale error vary?
It increases with increasing distance from standard parallels.
How to calculate the conversion angle on a conic chart?
CA = (∆λ · n) / 2
What is an alternative name for the convergence factor (on conic charts)?
Constant of the Cone.
How does the convergence factor change with varying latitude?
It doesn’t. It is constant.
Describe: the function of the Radio Magnetic Indicator.
It indicates the magnetic great circle track to an NDB.
How do rhumb line tracks and great circle tracks appear on Lambert’s conformal conic charts?
Rhumb lines are concave to the nearer pole.
Great circles are concave to the parallel of origin but assumed straight.
On Lambert’s conformal conic charts, how does the convergency vary with latitude?
It doesn’t.
Chart meridians are straight lines so the convergency is the same all over the chart.
How does the Lambert’s conformal conical projection solve the problem of thin usable area in simple conical projections?
By lowering the cone so that it cuts into the Earth.
How can we calculate the chart convergency on a Lambert’s conformal conic chart?
Chart convergency = ∆λ · n
What limits the usefulness of simple conic projections?
Small (long and narrow) area of constant scale.
Describe: convergence factor.
A standard measure of convergency.
It depends on the parallel of origin.
It equals the sine of the parallel of origin.
Another name for it is the constant of the cone.
Symbol: n.
Define: complex curve.
An S-shaped great circle track on a conic chart, where it crosses the parallel of origin.
Define: standard parallels.
Small circles along which the secant cone intersects the reduced Earth’s surface.
