A thousand years ago, one of the greatest scholars of the medieval Islamic era Iranian scientist-encyclopedist Abu Rayhan al-Biruni measured the Earth globe. He described the measurement process in his several treatises. Many of the more recent comments say that he received a very precise result, unrivaled until the New Time. The author provides a detailed analysis of Biruni’s measurement method, as well as an assessment of possible errors accompanying those measurements. Step by step the measurement process is reinstated; binding is made to specific places of observation, technical parameters of the instruments used are discussed. A parallactic method and instrument for measuring elevations proposed by Biruni is considered, which could only be put into practice in the 20th century. As a result of the research it was shown that Biruni’s method is not as accurate as it was believed. In addition, it is difficult to compare the unit of the length measurement used at Biruni’s time with modern ones.