back hoe loader bhl operation of the arm assembly 118 known as the back hoe is similar to operation of the arm assembly 18 of machine 10 operation of the front loader arm 190 and shovel 192 is well known in the art but in summary hydraulic rams are able to lift and lower the front loader arm 191 and further hydraulic rams are able to u201c crowd u201d or u201c dump u201d shovel 192 relative to the front loader arm 190 the back hoe loader 110 includes a monitoring unit 181 in this example the back hoe loader 110 replaces the machine 10 as indicated by the chain dotted lines of fig3 when considering fig3 the computer 72 receives information from the database 74 concerning an object in this case an underground gas pipeline 4 positioned 2 meters below the ground computer 72 receives information from the machine indicating that the machine has a back hoe capable of reaching 3 meters below ground level the back hoe loader is stationary with an engine speed that is relatively high and relatively constant and with an oil pressure and hydraulic system which is varying with time the computer can therefore determine that the back hoe loader is being used to dig ground with the back hoe the computer can determine that the maximum depth of back hoe 3 meters is lower than the depth of the gas pipeline 2 meters the computer can determine that the back hoe loader is being operated in the vicinity of the pipeline accordingly there is a raised probability that damage to the pipeline.