When measuring a dimension, the greatest possible error can be estimated based on the precision of the measuring instrument. Typically, if a measurement is made to one decimal place (as with 1.1 m), the greatest possible error is half of the smallest unit of measurement.
In this case, since the measurement is given to one decimal place, the smallest unit is 0.1 m. Therefore, the greatest possible error would be:
\[ \text{Greatest possible error} = \frac{0.1 , \text{m}}{2} = 0.05 , \text{m} \]
Thus, the greatest possible error of your measurement is 0.05 m.