Create the Tissot Indicatrix.
tissot( lambda, phi = NULL, degrees = TRUE, A = 6378137, f.inv = 298.257223563, ..., proj.in, proj.out )
Arguments
| lambda | longitude |
|---|---|
| phi | latitude |
| degrees | logical, work in degrees or radians |
| A | ellipsoidal semi-major axis (meters) |
| f.inv | the inverse flattening |
| ... | passed to internal function |
| proj.in | projection of input |
| proj.out | projection of context |
Value
list with stuff as per below
Details
Compute properties of scale distortion and Tissot's indicatrix at location x = c(lambda, phi) using prj as the projection. A is the ellipsoidal semi-major axis (in meters) and f.inv is the inverse flattening. The projection must return a vector (x, y) when given a vector (lambda, phi). (Not vectorized.) Optional arguments ... are passed to prj. Source: Snyder pp 20-26 (WGS 84 defaults for the ellipsoidal parameters). All input and output angles are in degrees.
Examples
x <- seq(-175, 175, by = 15) y <- seq(-82.5, 82.5, by = 15) xy <- expand.grid(x, y) r <- tissot(xy, proj.in= "OGC:CRS84", proj.out= "+proj=robin") j <- which.min(abs(135 - r$lon) + abs(54 - r$lat)) idx0 <- indicatrix0(r[j, ], scale=10^4, n=71) op <- par(mfrow = c(2, 1)) plot(idx0, add = FALSE) idx <- indicatrix(r, scale=3e5, n=71) plot(idx, add = FALSE)#>
