# What parameters do azimuthal and transverse cylindrical projection in secant case have as proj4 string

conical equal-area projection, secant case has e.g.

``````+proj=aea +lat_1=... +lat_2=... +lon_0=... +lat_0=... +x_0=... +y_0=... etc...
``````

I would ask if there is such thing, for transverse cylindrical equal-area, secant case? e.g:

``````+proj=tcea +lon_1=... +lon_2=... +lon_0=... +lat_0=... +x_0=... +y_0=... etc...
``````

and what is for the azimuthal equal area, secant case, I know just this for tangent case

``````+proj=laea +lat_0=... +lon_0=... +x_0=... +y_0=... etc...
``````

what should one add to get secant case not only tangent at a point?

Edit:

The transverse cylindrical equal area projection can be made into a secant case by specifying a scale factor with the `+k_0=` parameter. The secant lines (standard circles) of such a projection do not follow meridians, there are no "standard meridians", and using `+lon_1 +lon_2` would be ambiguous, so they are not used. Therefore we indicate a scale factor that will allow two small circles to be standard (no distortion).
• The relationship would be `k_0 = acos(dLon)` where dLon is the angular separation at equator between the central meridian and the standard circles (for the spherical case). Dec 6 '18 at 12:46
• Oops, my bad, it's `cos`, not `acos`, so `k_0 = cos(dLon)` Dec 6 '18 at 15:03