A server, comprising: a communication transceiver, configured for transmitting and receiving signals; and a processor, coupled to the communication transceiver, and the processor is configured for: receiving, through the communication transceiver, a first measurement report, wherein the first measurement report is related to a first network performance measurement of a user equipment, named UE hereinafter, with at least one mobile network, and the first measurement report comprises a plurality pieces of first location information of the UE, and each of the plurality pieces of first location information has time information; receiving, through the communication transceiver, a second measurement report, wherein the second measurement report is related to a second network performance measurement of the UE with the at least one mobile network; determining second location information of the UE according to a monitoring result obtained from the second measurement report, wherein the second location information has time information, and the monitoring result is related to signal transmission condition of the UE in the at least one mobile network; and calibrating the second location information according to the first location information, wherein the processor is configured for calibrating by: comparing the time information of each of the plurality of pieces of first location information with the time information of the second location information of the UE; and using the first location information with matched time or closest time information to modify the second location information. a communication transceiver, configured for transmitting and receiving signals; and a processor, coupled to the communication transceiver, and the processor is configured for: receiving, through the communication transceiver, a first measurement report, wherein the first measurement report is related to a first network performance measurement of a user equipment, named UE hereinafter, with at least one mobile network, and the first measurement report comprises a plurality pieces of first location information of the UE, and each of the plurality pieces of first location information has time information; receiving, through the communication transceiver, a second measurement report, wherein the second measurement report is related to a second network performance measurement of the UE with the at least one mobile network; determining second location information of the UE according to a monitoring result obtained from the second measurement report, wherein the second location information has time information, and the monitoring result is related to signal transmission condition of the UE in the at least one mobile network; and calibrating the second location information according to the first location information, receiving, through the communication transceiver, a first measurement report, wherein the first measurement report is related to a first network performance measurement of a user equipment, named UE hereinafter, with at least one mobile network, and the first measurement report comprises a plurality pieces of first location information of the UE, and each of the plurality pieces of first location information has time information; receiving, through the communication transceiver, a second measurement report, wherein the second measurement report is related to a second network performance measurement of the UE with the at least one mobile network; determining second location information of the UE according to a monitoring result obtained from the second measurement report, wherein the second location information has time information, and the monitoring result is related to signal transmission condition of the UE in the at least one mobile network; and calibrating the second location information according to the first location information, wherein the processor is configured for calibrating by: comparing the time information of each of the plurality of pieces of first location information with the time information of the second location information of the UE; and using the first location information with matched time or closest time information to modify the second location information. comparing the time information of each of the plurality of pieces of first location information with the time information of the second location information of the UE; and using the first location information with matched time or closest time information to modify the second location information.