Fixed spelling errors

chapters/background.tex

@@ -8,7 +8,7 @@ This method is very expensive and time-consuming, and LKAB would like to find a
     An onboard laser should map the walls of the shaft, and some collision avoidance should be implemented to facilitate semi-autonomous operation.
     Data should be passed on to a base station using UWB radio, which also acts as control for the drone.
     The base station should receive sensor data and, using LabVIEW, construct an easily understandable representation of the mine shaft.
-    It should also be able to issue high-level control of the drone, using only simple commands.
+    It should also be able to issue high-level control of the drone, using only simple commands such as ``up'' or ``down''.
 \subsection{Problem Formulation}
     Is it feasible to use a drone with laser measuring to measure a tilted mineshaft width, and for the process to be cheaper than current methods?
 \subsection{Assignment limitations}