Acutally, I live in Jerusalem and what Yossi said is true, that is if we understand what the original commentor was referring to. I have the compass, and it has a mechanical recalibrator so that when ever you travel from country to country, you can re-set it one time, “just like your watch”, and it will alway point in the proper direction. If you live in Israel as I do, so there is no difference. When you travel to Tel Aviv it is set for Tel Aviv, if you travel to Be’er Sheva, down South, so it has a recalibration for each city in Israel. It makes no difference if you travel N,S,E or West, it is recalibrated just as you would do when travelling through different international countries. The first comment above is confusing as the term, “margin of error” is used. there is no margin of error when one travels N,S. E. or W wether in the U.S. or in Israel etc. As long as one adjusts the compass in accordance with the proper instructions. Even in Jerusalem there are settings for different neighborhoods, so in this case it is not pointing to Jerusalem, but rather to Har habais. Some Rabbi’s use the compass for weddings to know in which direction to face the chupah. “Margin of error”, can only be understood to refer to something that is not functioning proplerly, i.e. even when you follow the instructions. So, if you are in Tel Aviv, and the compass is NOT functioning properly, i.e. maybe there is some metal too close to it, and we all know what metal (iron) will do to a magnetic compass. So, since one is relatively close to Jerusalem,(about 40 miles), since they are so close, even if the compass is a little bit off,i.e 5 degrees etc, due to some “margin of error”, it will still be pointing to Jerusalem. But, if 5,000 miles away, something is causing the compass to malfunction as stated, the same 5 degrees would be much more of a significant descrepency than if close to Jerusalem. The part above about the “world being round”, I am not sure what that refers to. Firstly the world is NOT round but more pumpkin shaped. And, what does it mean that no matter which way you face you will be facing, Jerusalem, Mecca etc. I guess this is probably some Letzanus.

now, move to the east, so that you are to the S of jerusalem, and your compass will point to the NE still, whereas it should really point N. move further east, so that you are in the SE of jerusalem, and your compass will be way off.

of course, once you are in jerusalem then it will always point at jerusalem

But, as far as the Jerusalem Compass is concerned, this is no problem, because in reality the compass is used as an aid to help one “face” in the direction of Jerusalem without the need of maps etc. So, this an item that works as accurately as a magnetic compass, and it has the added feature, that it provides the illusion that the needle itself is pointing against nature. I know, because I own one

By the way, just a bit of caution, anyone who is at all observant in any religion should be careful of looking the the failedmessiah. Their name is what they are all about. They are over flowing with Loshon Horah, Motzei Shem rah, everything haveing to do with evil speach and defamation of anything that breathes. There is an entire book written about this topic by the Chofetz Chaim, and they and those who listen to them are not in for a pleasent end.

Those who desire life….Guard your tongue from Evil….