A electromagnetic survey apparatus for measuring electrical properties of subsurface earth features, comprising: a transmitter for providing electric power for an electric current within the subsurface forming an electromagnetic field; a borehole electrode (20, 24) positioned within a well borehole at a depth of interest; a wellhead electrode at the earth surface adjacent the borehole; a counter electrode at the earth surface and at a spaced position from the borehole; a switching mechanism for selectively electrically connecting the transmitter to the borehole electrode (20, 24) and the wellhead electrode or to the borehole electrode (20, 24) and the counter electrode for electrical current to flow between the connected electrodes and form an electromagnetic field for assessing electrical properties of a subsurface formation of interest; the switching mechanism also arranged to selectively electrically connect the transmitter to the wellhead electrode and the counter electrode for electrical current to flow between the connected electrodes and form an electromagnetic field for assessing the presence of near surface anomalies; an array of electromagnetic sensors at the earth surface disposed to sense the electromagnetic field between the connected electrodes; a data processor arranged to form a measure of resistivity of the subsurface formation of interest from the sensed electromagnetic field between the borehole electrode (20, 24) and the wellhead electrode or between the borehole electrode (20, 24) and the counter electrode; the data processor arranged to form a measure of resistivity of near surface anomalies (40, 42) from the sensed electromagnetic field between the wellhead electrode and the counter electrode; and the data processor further arranged to remove effects of near surface anomalies (40, 42) from the measure of resistivity of the subsurface formations of interest for assessing electrical properties of the subsurface formation of interest. a transmitter for providing electric power for an electric current within the subsurface forming an electromagnetic field; a borehole electrode (20, 24) positioned within a well borehole at a depth of interest; a wellhead electrode at the earth surface adjacent the borehole; a counter electrode at the earth surface and at a spaced position from the borehole; a switching mechanism for selectively electrically connecting the transmitter to the borehole electrode (20, 24) and the wellhead electrode or to the borehole electrode (20, 24) and the counter electrode for electrical current to flow between the connected electrodes and form an electromagnetic field for assessing electrical properties of a subsurface formation of interest; the switching mechanism also arranged to selectively electrically connect the transmitter to the wellhead electrode and the counter electrode for electrical current to flow between the connected electrodes and form an electromagnetic field for assessing the presence of near surface anomalies; an array of electromagnetic sensors at the earth surface disposed to sense the electromagnetic field between the connected electrodes; a data processor arranged to form a measure of resistivity of the subsurface formation of interest from the sensed electromagnetic field between the borehole electrode (20, 24) and the wellhead electrode or between the borehole electrode (20, 24) and the counter electrode; the data processor arranged to form a measure of resistivity of near surface anomalies (40, 42) from the sensed electromagnetic field between the wellhead electrode and the counter electrode; and the data processor further arranged to remove effects of near surface anomalies (40, 42) from the measure of resistivity of the subsurface formations of interest for assessing electrical properties of the subsurface formation of interest.