to the side of the transmitting sonde Draw a straight line through
these two null spots
(c) Next set the locating mode to PEAK and hold the receiver vertical and
rotated so that the line just drawn through the side nulls is oriented
side to side with respect to the receiver Also the receiver should be
offset forward or back from the line through the side null marks
(d) With the receiver thus oriented walk side to side and search for
another null Once you have located and marked the null on one side of
the first line mark the accompanying null on the other side of the line
You have now located two “end nulls” so called because they are found
off of the ends of the sonde
(e) Draw a straight line through the two end nulls Assuming the sonde
rests in a roughly horizontal position underground the intersection of
the two lines will mark the surface location directly above the sonde
Determining Sonde Depth by Triangulation
Once the surface location of a sonde has been established using the null
method the operator may determine depth by triangulation To do this set
the locating mode to PEAK As before hold the receiver vertically during this
procedure
(a) Position the receiver so that the pointer is directly above the surface
location and orient it so that the end null line runs side to side
(b) Move the receiver to the right or left along the end null line until a null
is detected Narrow in on the null spot and mark it Now move the
receiver the opposite direction along the end null line to mark the
accompanying null spot You have located the “depth nulls”
