Coal seam attitude: square 300 m

Method: the coal seam is a plane. Take A (SW corner) as origin, x east, y north. B (SE) = (300, 0), C (NW) = (0, 300).

Data

Depth gradients

$$\begin{aligned} a &= \frac{45 - 15}{300} = 0.10\ \text{(depth increases eastward)} \\ b &= \frac{60 - 15}{300} = 0.15\ \text{(depth increases northward)} \end{aligned}$$

Depth $d = 15 + 0.10\,x + 0.15\,y$.

Dip and dip direction

$$\tan\delta = \sqrt{0.10^2 + 0.15^2} = 0.1803 \Rightarrow \delta = 10.22^\circ$$ $$\text{dip direction} = \arctan\left(\frac{0.10}{0.15}\right) = 33.69^\circ\ \text{from north (NNE)}$$

The strike is perpendicular: $33.69^\circ - 90^\circ = -56.31^\circ$, i.e. N56.3°W (= 303.69°).

Answer: attitude of the coal seam = strike N56.3°W, dip 10.2° towards N33.7°E (NNE).