To monitor nuclear and radiation emergencies, it is crucial to obtain accurate in situ measurements of the environmental \(\gamma\) radiation dose rate from key radionuclides, particularly for large radioactive surface sources. The methods currently used for measuring dose rates are inadequate for obtaining the dose rates of key radionuclides and have large angular response errors when monitoring surface sources. To address this practical problem, this study proposes three methods for measuring the dose rate: the weighted peak total ratio, mean value regression, and numerical integration methods. These methods are based on energy-spectrum measurement data, and they were theoretically derived and numerically evaluated. Finally, a 1-m-long hexagonal radioactive surface source was integrated into a larger surface source. In situ measurement experiments were conducted on a large radioactive surface source using a dose-rate meter and a portable HPGe \(\gamma\) spectrometer to analyze the errors of the three aforementioned methods and verify their validity.
