French astronomer, topographer, and surveyor. Worked with Cassini I (1625-1712) and Ole Römer (1644-1710). Took part in the measurement of a meridian arc and, with the astronomer and mathematician Philippe de la Hire (1640-1718), in operations to determine the coordinates of many French towns. Improved astronomical instruments and surveying instruments, fitting the latter with telescopes and a micrometer of his invention. One of the first members of the Académie Royale des Sciences of Paris. Launched Connaissances du temps, a periodical still published today. Picard may be regarded as one of the founders of modern astronomy in France.