How did Islamic scholars preserve and expand Ptolemy’s cartographic ideas?

Islamic scholars played a pivotal role in preserving and advancing the cartographic legacy of Ptolemy during the Middle Ages, a period when such knowledge was largely neglected in Europe.1

Key contributions include:

• Translation and Preservation: Scholars in the Islamic world translated Ptolemy’s major treatises, ensuring the survival of his geographical and astronomical traditions.1
• Refinement of Data: The mathematician al-Khwārizmī authored Kitāb ṣūrat al-arḍ ("The Image of the Earth"), which utilized Ptolemy’s coordinate system as a foundation while providing more accurate values for the length of the Mediterranean Sea and the locations of various cities in Asia and Africa.2
• Scientific Expansion: Islamic astronomers and geographers actively built upon Ptolemy’s work by conducting their own measurements. For example, they measured a portion of the Earth’s meridian to refine understanding of its size. They also integrated trigonometry and advanced stereographic projection techniques—often to determine the qiblah (the direction to Mecca)—which enhanced the mathematical precision of their maps and instruments like the astrolabe.13
• Innovative Mapping: Scholars such as al-Idrīsī synthesized Greek and Arabic geographical knowledge with firsthand reports to create sophisticated world maps, such as the one constructed for King Roger II of Sicily.14