We present new results using energetic particles to remotely sound the high-latitude magnetopause in three-dimensions. Less than two gyro radii from an absorbing boundary a trapped particle distribution appears non-gyrotropic, as particles start to cross the boundary. Knowing the magnetic field and the particle mass and energy, it is possible to derive the direction and distance to the magnetopause just by examining the azimuthal distribution of locally mirroring particles. Combining observations from at least three spacecraft gives a three-dimensional picture of the magnetopause surface. We have performed this analysis for a high-latitude boundary crossing on January 14, 2001. The very first results give a consistent overall picture of how the magnetopause boundary is coming towards, just passing, and then retreating away from the spacecraft. This clearly illustrates that the magnetopause ion sounding technique can be used to remotely study the three-dimensional orientation and location of the magnetopause surface.