If h1 and h2 are the differences in level between ground and the formation levels, m is the slope of the sloping sides. D is the distance between the cross sections then, prismoidal correction for a level section is

• D/2m(h1 - h2)
• D/3m(h1 - h2)
• D/6m(h1 - h2)2
• D/6m(h1 - h2)3
• D/6m(h1 + h2)2