Overlapping receiver spreads :

You need a maximum shot-geophone offset of 6 times the maximum target 
depth. If you insist on a maximum target depth of 150 meters, then the 
maximum shot-geophone offset required is at least 900 meters. I 
recommend to use a geophone spacing of 10 meters, with your 48 channel 
spread. Some of our clients regularly use our software, with such a 
receiver spacing. Use an overlap of 22 geophones, between adjacent 
spread layouts. See below.

Then shoot into the first spread layout from maximum far reverse offset 
at 480 meters to right of last receiver. Shoot into the last spread 
layout from a maximum far forward offset at 480 meters to left of first
receiver. For receiver spread layouts and shot positions, please refer 
to the following graphics :


 +--+--+--+--+--+--+--+--+  +  +  +  +  +  +  +  +     :  first spread

  +  +  +  +  +--+--+--+--+--+--+--+--+  +  +  +  +    :  second spread
 
   +  +  +  +  +  +  +  +  +--+--+--+--+--+--+--+--+   :  third spread

The "+" symbol means a shot position. The "--------" line represents 
the 48 channel receiver spread. One character column corresponds to a 
distance of 20 meters. The shot spacing is 60 meters, receiver spacing 
is 10 meters.

The second spread is moved 260 meters to the right, in relation to the 
first spread. Shot stations don't coincide between adjacent spreads, 
but are "staggered", i.e. moved 20 meters to the right. Receiver stations 
do coincide, in the overlapping section of two adjacent spread layouts.

Since all shots "+" are positioned within or directly adjacent to at 
least one receiver spread layout, all shots can be used for WET true 2D 
tomography processing. In the context of WET processing, all spreads are 
"active" at the same time.


We recommend to use a mobile weight drop as an energy source. See e.g.

http://www.geoexpert.ch/en/us/drop.shtml#vaki (in English), and
http://www.geoexpert.ch/it/us/drop.shtml#VAKI (in Italian).