A lidar system for detection of a gas comprises an optical transceiver for transmitting and receiving optical radiation. A method of operating the system comprises performing spatially scanned sensing measurements of the gas across a system field of view, and analyzing the sensing measurements to determine the presence and location of excess of the gas in the system field of view. Based on the determined location, an adjusted system field of view is determined and spatially scanned sensing measurements of the gas are performed across the adjusted system field of view to obtain sensing measurements at higher spatial resolution.