1. An electromagnetic manuscript input method, applicable for an electromagnetic manuscript input apparatus comprising an electromagnetic pen and a digitizer to obtain coordinates of the electromagnetic pen on the digitizer, the digitizer having a plurality of horizontal windings arranged in parallel along a horizontal direction and a plurality of vertical windings arranged in parallel along a vertical direction, and the electromagnetic manuscript input method comprising: emitting a driving control signal by a coordinate controller of the digitizer, to drive a driving circuit of the digitizer, thus emitting a driving signal by the driving circuit to a first horizontal winding and a first vertical winding of the digitizer; detecting an induction potential with a detection circuit of the digitizer, wherein the induction potential is generated according to induction of the first horizontal winding or the first vertical winding to an electromagnetic wave emitted by the electromagnetic pen; converting the induction potential into a first digital signal with an analog-to-digital (ADC) converter, and transmitting the first digital signal to the coordinate controller, wherein the coordinate controller comprises a processor; recording the first digital signal by the processor in the coordinate controller, and transmitting a second driving control signal to a second horizontal winding or a second vertical winding; performing a detection and conversion operation with the detection circuit and the ADC, to generate a second digital signal and transmit the second digital signal to the coordinate controller; comparing the first digital signal with the second digital signal to find out a larger one, and recording the larger one of the first digital signal and the second digital signal by the processor of the coordinate controller; transmitting a third driving control signal by the coordinate controller, and performing a detection and conversion operation to the third driving control signal with the detection circuit and the ADC, to generate a third digital signal corresponding to the third driving control signal, and comparing the third digital signal with the recorded larger one to determine and record an updated larger digital signal; repeatedly transmitting driving control signals and performing the detection and conversion operations until all of the horizontal windings and the vertical windings have been conducted with the detection and conversion operations to determine a finally updated larger digital signal and the corresponding horizontal and vertical windings having a maximum induction potential and record a maximum horizontal position and a maximum vertical position corresponding to the horizontal winding and the vertical winding having the maximum induction potential by the processor; obtaining two adjacent horizontal positions and two adjacent vertical positions, immediately adjacent to the maximum horizontal position and the maximum vertical position, respectively, and recording the three horizontal positions and the three vertical positions with the processor; emitting corresponding driving signals according to the three horizontal positions and the three vertical positions by the processor of the coordinate controller, and recording six corresponding induction potentials with the processor; and calculating the coordinates of the electromagnetic pen with a coordinate algorithm corresponding to a Gauss distribution function of the induction potentials; wherein the coordinate algorithm uses the following equation to calculate the coordinate D of the electromagnetic pen in the horizontal or vertical direction: 
 D=XP 0 +T /2*ln( VPR/VPL )/ln( VP 0 2 /VPR/VPL ), wherein XP 0 and VP 0 are the coordinate and corresponding induction potential of the maximum horizontal or maximum vertical position, VPR and VPL are the corresponding induction potentials of the two adjacent horizontal or vertical positions, T is a coordinate value of a space between two neighboring horizontal or vertical windings, and ln represents a logarithm function.