This is used by `topoInterpolate`

.

bilinearInterp(x, y, gx, gy, g)

x | vector of x values at which to interpolate |
---|---|

y | vector of y values at which to interpolate |

gx | vector of x values for the grid |

gy | vector of y values for the grid |

g | matrix of the grid values |

vector of interpolated values