N 39° 08' N , W 84° 30' - Cincinnati, OH - Gaithersburg, MD
Posted by: 
Ernmark
N 39° 08.203 W 077° 11.916
18S E 309976 N 4334250
The walkway at a now-unused observatory contains stones with the longitude and elevation of 5 other observatories at the same latitude, which together with this one, were used to measure the wobble of the Earth.
Waymark Code: WMNV3T
Location: Maryland, United States
Date Posted: 05/04/2015
Views: 3
This observatory was built in 1899 & along with 5 other observatories built at the same latitude made observations of specific stars. The information was used to calculate the wobble of the Earth's axis.
The other original observatories were located in California, Ohio, Italy, Japan, & Turkestan - all along 39° 08' latitude.
These observatories continued to operate until 1982, when GPS technology rendered them obsolete, although data collected during their operation continues to be of use.
The observatory building as well the 5 geodetic survey marks on-site are included in the National Register of Historic Places. The grounds are now maintained by the City of Gaithersburg as a park.
The 2 slabs at this location note the location & elevation of the closest observatory to this one - Cincinnati, Ohio.
For information on the other observatories - (
visit link)