A theodolite is set up at station $\mathrm{A}$ and a $3 \mathrm{~m}$ long staff is held vertically at station $\mathrm{B}$. The depression angle reading at $2.5 \mathrm{~m}$ marking on the staffis $6^{\circ} 10^{\prime} .$ The horizontal distance between $\mathrm{A}$ and $\mathrm{B}$ is $2200 \mathrm{~m} .$ Height of instrument at station $\mathrm{A}$ is $1.1 \mathrm{~m}$ and $\mathrm{R.L} .$ of $\mathrm{A}$ is $880.88 \mathrm{~m} .$ Apply the curvature and refraction correction, and determine the R.L. of $\mathrm{B}$ (in $\mathrm{m}$ ).
A theodolite is set up at station $\mathrm{A}$ and a $3 \mathrm{~m}$ long staff is held vertically at station $\mathrm{B}$. The depression angle reading at $2.5 \mathrm{~m}$ marking on the staffis $6^{\circ} 10^{\prime} .$ The horizontal distance between $\mathrm{A}$ and $\mathrm{B}$ is $2200 \mathrm{~m} .$ Height of instrument at station $\mathrm{A}$ is $1.1 \mathrm{~m}$ and $\mathrm{R.L} .$ of $\mathrm{A}$ is $880.88 \mathrm{~m} .$ Apply the curvature and refraction correction, and determine the R.L. of $\mathrm{B}$ (in $\mathrm{m}$ ).