Frequently asked questions

What is the 'Weight by time' used for and do I need to use it?

Weight by time allows you to give a heavier weight to some places and less weight to other places. For example, if you lived at address 1 for 3 years and at address 2 for 1 year, the midpoint would be significantly closer to address 1 than address 2.

Using weighting factors like 'Weight by time' and 'Other weight' is optional. If you leave the years, months, days, and weight boxes blank, all of your places will be weighted equally for the calculation. If you leave the weight blank for address 1 and address 2, the midpoint will be exactly halfway between the two addresses.

I added an address or city, but it found the wrong place, what should I do?

Remove it, then type it in again, and be sure to include the state or country name.

While I was adding a long list of addresses, I noticed the calculator slowing down quite a lot. Is this normal?

Adding hundreds of red place markers to the map gives browsers a fairly heavy processing load. This tends to slow down the calculator considerably as more and more markers are placed on the map.

If you uncheck the option 'Display place markers', the midpoint will be calculated and only the 'M' marker will be placed on the map. This can speed up the process of adding large numbers of addresses considerably.

I added two places to the map, but the midpoint doesn't appear to be properly lined up with my two places. What is the reason for this?

This is due to the distortion that occurs when a spherical earth is projected onto a flat map. If you stretch a string between your two locations on a world globe, you will see that the midpoint is in the correct place.

If I choose the North Pole and give it a weight of 2, then I choose a point on the equator and give it a weight of 1, why does the calculator say the midpoint is at 63.43 N latitude instead of 2/3 the distance from the equator to the North Pole at 60 N?

The center of gravity method assumes that all points on a sphere are points in 3-dimensional space and distances are not calculated on the curve of the earth. The true center of gravity for the two places would be 2/3 the distance along a straight tunnel through the interior of the earth between the equator and the North Pole. A line can be drawn from the center of the earth through this point and extended out to the surface of the earth. This point on the earth's surface is the geographic midpoint and in this case is at 63.43 N latitude rather than 60 N.

GeoMidpoint has performed experiments, observing the effects of gravity on disks weighted at various locations, and has verified that the center of gravity calculations are correct.

Geographic Midpoint Calculator