Performance evaluation of automatic vis-à-vis manual topographic survey for precision land levelling

Laser land levelling has contributed immensely to irrigation water saving to cope with declining ground water tables in South Asia. A topographic survey of a field is a pre-requisite to achieve high accuracy in land levelling. Presently, manual topographic surveys are conducted before using a laser land leveller in South Asia, which is cumbersome, time consuming and requires substantial operator skill. A novel sensor-based automatic topographic survey is potentially more precise and cost-effective. Therefore, a field study was conducted to compare the efficiency of a tractor operated sensor-based automatic survey system attached to a laser leveller compared with the conventional manual topographic survey. The automatic survey system consisted of automatic functioning of the laser operated power mast and scraper. The automatic survey method significantly reduced the earthwork and levelness index by 74.0 and 75.4% compared with 61.5 and 62.1% for manual topographic survey, respectively. The automatic survey improved the land uniformity coefficient by 78.4% compared with 42.4% for the manual survey. Average fuel consumption and field capacity were 56.5% and 48% higher for automatic survey compared to manual topographic survey method. The average survey cost was 38.2% lower for automatic survey compared with manual survey. The field capacity of the laser leveller (including the time taken for field survey) was significantly higher by 53% for automatic survey than manual survey. The total cost of operation of automatic survey method was 30.1% lower compared with conventional manual survey. Based on the results from this study, the newly developed automatic survey system is superior to conventional manual survey method in terms of precision in land levelling and economic gains.