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Frisius, Gemma
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1508-1555 |
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Of German extraction, Gemma Frisius became the foremost astronomer, mathematician and surveyor of his time. He was an influential figure, not only for his teaching of Mercator at his School of Geography at Louvain but for his scientific contributions to practical aspects of cartography. He invented an improved form of cross-staff for astronomical use and in his book A Method of delineating places he set out the principle of triangulation in map making. Later, he was the first to suggest the use of portable clocks to determine longitude.
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