Some places on earth have different gravities. Gravity roughly decreases with altitude, and many things can affect it. The linked article explains that the European Space Agency are trying to get a better image of the earth’s gravitational pull. There is also some talk about how this study can help us understand climate models better.
Probe launches to map Earth’s gravity in best detail yet. (via New Scientist)
They have a disclaimer right on the webpage about copying content, so I used an image from NASA. Click through to see their video on the subject.
Some more links for you: