The invention discloses a
ratio method for correcting topographic influence in electromagnetic
prospecting. The
ratio method comprises the steps of acquiring a
surface layer resistivity value without topographic influence to serve as a standard resistivity of
topographic correction; drawing an in-line
topographic profile, respectively comparing the
topographic profile with a frequency point profile of a
frequency domain electromagnetic method and a time channel profile of a
time domain electromagnetic method, and judging the topographic influence suffered by the actually measured data according to the influence rule of the
topography on the resistivity in the
frequency domain and the
time domain electromagnetic field; observing from the highest frequency point of the
frequency domain electromagnetic method and the earliest time channel of the
time domain electromagnetic method so as to obtain the topographic response which is closest to the
surface layer until the absence of low-frequency frequency point of the topographic influence is observed in the frequency domain electromagnetic method and the absence of the late time channel of the topographic influence is observed in the time domain electromagnetic method, and acquiring the
observation data without topographic influence; and performing
topographic correction according to a ratio formula of pcorrected(i,j)=pmeasured(i,j) [pstandard(i) / pmeasured(i,l)]C(i,j). The
ratio method is good in correction effect in the process of correcting the topographic influence, is high in feasibility and can be widely applied to topographic influence correction in electromagnetic
prospecting.