The US is tilted. Florida is about right. Seattle is a meter high.
The U.S. Is Getting Shorter, as Mapmakers Race to Keep Up https://www.nytimes.com/2020/05/22/science/maps-elevation-geodetic-survey.html But across the United States, the heights of structures, landmarks, valleys, hills and just about everything else are about to change, at least with regard to average sea level. Most will get shorter. Parts of the Pacific Northwest will shrink by as much as five feet, and parts of Alaska by six-and-a-half, according to Juliana P. Blackwell, director of the National Geodetic Survey. Seattle will be 4.3 feet lower than it is now. That's because height is only height compared to a reference point -- and geodesists, who calculate the Earth's shape, size, gravitational field and orientation in space over time, are redefining the reference point, or vertical datum, from which height is derived. It is a fiendishly difficult math and physics task that, once completed, will have taken a decade and a half to accomplish. --- But making highly detailed measurements of the gravitational field, in order to factor them into heights captured by GPS, is no small task. In 2007, the National Geodetic Survey launched an ambitious mission -- GRAV-D, for Gravity for the Redefinition of the American Vertical Datum -- to accomplish just that. -- These are my opinions. I hate spam. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.