Units & Standards

"Measuring base with Invar tape, Stanfield, Oregon (NOAA Photo Library theb1656)" by U.S. Coast and Geodetic Survey — https://commons.wikimedia.org/wiki/File:Theb1656_-_Flickr_-_NOAA_Photo_Library.jpg — Public domain (work of the U.S. federal government, 17 U.S.C. §105; also released by the NOAA Photo Library under CC BY 2.0)

"K20 and Friends: four of the five U.S. national prototype kilogram artifacts, including K20 (front) and K4 (back)" by J. Lee/NIST — https://commons.wikimedia.org/wiki/File:Kilograms-pml0013_K20_and_Friends_Four_of_the_five_U.S._national_prototype_kilogram_artifacts,_including_K20_(front)_and_K4_(back).png — Public domain (work of the U.S. federal government, 17 U.S.C. §105 (photograph by J. Lee of NIST, published by NIST in 2018); Commons also marks the file with the Public Domain Mark 1.0)

"Committee Meter Bar, made of platinum in 1799 (NIST Museum Collection)" by NIST Museum Collection — https://commons.wikimedia.org/wiki/File:Committee_Meter_Bar_Platinum_1799.png — Public domain (work of the U.S. federal government, 17 U.S.C. §105 (photograph from the NIST Museum Collection, source https://www.nist.gov/image/committee-meter); Commons also marks the file with the Public Domain Mark 1.0)

"Sextant (NPS Photo, Lewis and Clark National Historical Park)" by NPS Photo — https://commons.wikimedia.org/wiki/File:This_instrument_was_used_to_measure_the_angular_distance_between_the_moon_and_sun_or_a_star_for_determining_longitude._(1d68d331-1dd8-b71b-0bf5-2e79f90f1e7b).JPG — Public domain (work of the U.S. federal government, 17 U.S.C. §105 (Commons tag PD-USGov-NPS: material based on a work of a National Park Service employee created as part of official duties; photographer field NPS Photo, publisher U.S. National Park Service, source NPGallery); structured data: public domain in the United States, work of the federal government)