# Overlap contourplot and world map [duplicate]

I am trying to plot a list of {latitude,longitude,f(latitude,longitude)} values over a mercator projection. I tried a generic periodic function in spherical coordinates, but the output looks wrong. I was expecting a set of stripes equally separeted along the longitude. This is my code:

Inc = Pi/2;
f[θ_, Φ_] = Cos[6*Φ];
x = (Pi/2 - θ)*180/Pi;
y = (Pi - Φ)*180/Pi;
M = Table[{x, y, N[f[θ, Φ]]}, {θ, 0, π,
Inc/2}, {Φ, 0, 2 π, Inc}];
plot = ListContourPlot[M,
DataRange -> {{-90, 90}, {-180, 180}, Automatic}, Frame -> False,
InterpolationOrder -> 2, ImageSize -> 300, Contours -> 10,
ContourStyle -> None];
GeoGraphics[{GeoStyling[{"GeoImage", plot},
GeoRange -> {{-90, 90}, {-180, 180}}], Opacity[0.8],
GeoBoundsRegion["World"]}, GeoRange -> "World",
GeoProjection -> "Mercator",
GeoBackground -> {"Coastlines", "Land" -> White, "Ocean" -> White,
"Border" -> Black}]


And this is the result:

Can you help me? :)

Edit: Over here they used a different kind of function. I can't make my code work with that.

• related: GeoListPlot and ListContourPlot – kglr May 1 '18 at 22:33
• I tried ListContourPlot with reversed coordinates but I still can't make it work. – Rodrigo May 1 '18 at 22:59
• I used that question as a starting point for my code, but I can't make a generic function work with that code. – Rodrigo May 2 '18 at 0:05