Dip angle is the the angle of the geomagnetic field measured from the horizontal component of the field which points to true north.
b or gtotal are interchangeable, gtotal is an industry term. They measure the strength of the magnetic field in a given area.
Declination I assume you know.
Soil content varies, it is the ferrous we are concerned about here.
+1 degree angle from vertical, rig floor or platform down.
It is a trick question.
Gyros are only used, and there are many types for wells with an inclination. They present no value at vertical.
Magnetometers are all affected by the earth's magnetic field, strength, dip angle and ferrous content of the soil. As well as any metal we may have in the hole or from previous wells.
Gyros, are wether rate or laser-ring or mechanical are unaffected by the magnetics of the earth.
I can explain more later if you want. It is cool egg-head stuff. K when I get recharged for you just for asking. This is what pays my salary. Lots of other variables but again I can explain more later sleepy time now.
Check out
www.scientificdrilling.com for some more info and study for your test.