Going through flight school I got acquainted with the Lambert Conformal Conic projection, as it's the common projection for VFR sectional charts, and I think I have pretty good grasp of it, geometrically.
However, trying to wrap my head around the mathematics behind it I browse around on Wikipedia and on MathWorld which both more or less simply list the formulas, not really diving into the mathematics behind it.
It appears to have 4 parameters:
- The two standard parallels,
- reference longitude, and reference latitude
What is the purpose of the reference longitude/latitude? Do they affect the actual projection, or will they simply shift the result to let the reference coordinates result in (x,y)=(0,0)?
Best Answer
I think you have it "spot on" so to speak.
Fundamental to the geometry of any projection is the standard line or lines -- where the "paper" touches or cuts the globe before being "rolled flat" and where there is no linear distortion.
Then the practical issue is where to center the map, if it's not at 0, 0 (off the Gulf of Guinea): The center of your region of interest becomes the reference lat-long.
For a conic projection, the effect of the reference longitude will be to rotate your region of interest round to a prominent position. The map below (from wiki/Lambert_conformal_conic_projection) uses the default reference meridian, but if you wanted some other meridian to be "vertical"...