File:USGS Idaho Montana 1900 Survey Spokane Courthouse Astronomic Piers.jpg

Camera location	47° 39′ 52.52″ N, 117° 25′ 42.13″ W	View this and other nearby images on: OpenStreetMap	47.664590; -117.428369

Photo captions:

U.S. Geological Survey BULLETIN NO. 170 PL.IV 
ASTRONOMIC PIERS IN COURT-HOUSE GROUNDS AT SPOKANE, WASHINGTON. 
U.S. Geological Survey latitude pier in right foreground; U.S. Coast and Geodetic Survey longitude pier behind figure of man. 

Historic background: These stone monuments also known as astronomic piers next to the Spokane Courthouse cupola flagpole were used as base stations or benchmark reference points for latitude and longitude in the USGS "Survey of the Boundary Line Between Idaho and Montana from the International Boundary to the Crest of the Bitterroot Mountains." Surveyed in 1897-1898. Bulletin of the United States Geological Survey No. 170, Department of the Interior. Printed in 1900 by US Government Printing Office. Photographic and Drawn Plates (images) of the field work of the survey. The Idaho-Montana boundary used Stone Survey Monuments and Iron Post Survey Monuments. Placed into the Public Domain by government of USA. Printed more than 114 years prior to time of upload.

(excerpt from the USGS printed survey report) 1900 Survey Report: " This point is connected, by direct measurement, with longitude pier of the United States Coast and Geodetic Survey of 1888 and with latitude pier of the United States Geological Survey of 1896. It is also connected, by triangulation, with the stations of the base expansion. The point located is the center of the flagstaff, which is over the center of the cupola of the new court-house. "

USGS Idaho Montana Boundary 1897 Survey Control Diagram of Triangulation from Spokane Courthouse Astronomic Piers

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