[time-nuts] NYTimes: New geoid soon
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.
Re: [time-nuts] NYTimes: New geoid soon
On Fri 2020-05-22T23:16:49-0700 Hal Murray hath writ: > It is a fiendishly difficult > math and physics task that, once completed, will have taken a decade and a > half to accomplish. So fiendishly difficult that the first time the task was completed was not until 1899 The Transcontinental Triangulation and the American Arc of the Parallel Assistant CHAS. A. SCHOTT, Chief of the Computing Division, USC&GS ftp://ftp.library.noaa.gov/docs.lib/htdocs/rescue/cgs_specpubs/QB275U35no41900.pdf -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m ___ 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.
Re: [time-nuts] NYTimes: New geoid soon
On 5/23/20 11:52 AM, Steve Allen wrote: On Fri 2020-05-22T23:16:49-0700 Hal Murray hath writ: It is a fiendishly difficult math and physics task that, once completed, will have taken a decade and a half to accomplish. So fiendishly difficult that the first time the task was completed was not until 1899 And how long did Mr. Schott and the team work on it? What about the Clarke 1866 spheroid? A book about the Indian subcontinent measuring: "The Great Arc" by John Keay is also good. These days, in the US, making similar measurements we don't have to worry too much about being eaten by tigers. The Transcontinental Triangulation and the American Arc of the Parallel Assistant CHAS. A. SCHOTT, Chief of the Computing Division, USC&GS ftp://ftp.library.noaa.gov/docs.lib/htdocs/rescue/cgs_specpubs/QB275U35no41900.pdf -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m ___ 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. ___ 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.
Re: [time-nuts] NYTimes: New geoid soon
On Sat 2020-05-23T12:21:17-0700 jimlux hath writ: > > So fiendishly difficult that the first time the task was completed was > > not until 1899 > > And how long did Mr. Schott and the team work on it? The reason that this report was in the Lick library is that the observatory hosted one of the sites in 1888. google will reveal scans of a lot of the preliminary reports for the traverse in parts farther east. -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m ___ 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.
Re: [time-nuts] NYTimes: New geoid soon
In a similar vein I recommend “The Measure of All Things,” by Ken Alder, the story of Méchain and Delambre and the history of the meter. (Published by The Free Press in 2002.) On Sat, May 23, 2020 at 1:07 PM Steve Allen wrote: > On Sat 2020-05-23T12:21:17-0700 jimlux hath writ: > > > So fiendishly difficult that the first time the task was completed was > > > not until 1899 > > > > And how long did Mr. Schott and the team work on it? > > The reason that this report was in the Lick library is that the > observatory hosted one of the sites in 1888. google will reveal scans > of a lot of the preliminary reports for the traverse in parts farther > east. > > -- > Steve Allen WGS-84 (GPS) > UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat > +36.99855 > 1156 High Street Voice: +1 831 459 3046 Lng > -122.06015 > Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m > > ___ > 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. > -- Jeremy Nichols Sent from my iPad 6. ___ 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.
