overlay flux footprint over a map

Question

I need to overlay a plot over a map (it can be from ggmap or from a file in my pc - not a shapefile).

    ### Here is the map
    library(ggmap)
    library(RgoogleMaps)

    lat = 49.12978
    lon = -122.985
    center = c(lat, lon)
    bbmap <- get_map(location = c(lon, lat), zoom = 18, maptype = "satellite")

And here! is the data and the code to make the plot that I want to overlay.

    library(fields)
    image.plot(FFP$x_2d[1,],FFP$y_2d[,1],FFP$fclim_2d)

The main problem is that the plot uses distance to a point to generate a flux density plot, so there are no coordinates (I only have the center coordinates which I used to get the map)

This question is pretty much this! that hasn't been answered, but it seems that the solution is georeferencing the data. However, I don't know how to do that in R. I have tried using the "raster" function to create a 3D raster of the map and the image, using the extent of the map for both, but the plot seems not right because it looks like its rotated.

Ultimately, what I want is to have only the 90% or 80% contour line over the map, not the whole thing.

The final image should look something like this but showing only the most external line, reference image: from this webpage

Hope someone can help!

Thanks!