Approach your target like a normal backside 50-50 with a little speed and distance (depends on your style, but most likely a little less then 1 foot).
Pop a normal frontside 180, but make sure it is high enough to get overtop of your target. Doing the 180 should make you gap the distance between you and your target (sidways). Once overtop extend your feet and try to catch the edge so you land on a 50-50, except switch. When you land try not to fall forward, keep your knees bend and stay low. If you have trouble catching the ledge, try doing the frontside 180 and leaning back as you land, this way once you hit the ledge, your force will carry you into it and you should be able to balance out. Continue grinding until you have your balance. Then pop out or do your own thing to get out and ride away clean.
Good Luck!