Drone based LiDAR survey of Oil & Gas assets ..

Drone based LiDAR survey of Oil & Gas assets in the jungle of Gabon (80 000ha)
In difficult to reach places in Africa, LiDAR surveys are often prohibitively expensive and can take a long time to perform. Delays due to poor weather, long ferries and bureaucratic processes make it a challenge to undertake accurate and critical information regarding terrain conditions. Drone and LiDAR technology has evolved significantly in the past few years allowing high resolution data to be made available over some of the largest and remotest areas.

3DroneMapping was contracted by a prominent oil and gas producer in Gabon to perform a comprehensive survey of its assets and expansion projects. The requirements were to produce ground level DTM and high resolution orthomosaics over 80 000ha. This data would help engineers better plan for pipeline routes and road extensions between new extraction platforms.

The entire site is covered with dense rainforest jungle with very little access tracks and much of it only accessible via barges on a river system. The only other human activities in the area are other oil and gas producers and forestry. Much of the rainforest is untouched with little human impact.

Using a specialized fixed wing VTOL (vertical take off and landing) drone, the project could be surveyed with an adapted LiDAR scanner. The 3.4m wingspan drone used for the project is specially modified for long range and heavy lift capabilities that can carry a 3kg scanner unit for up to 3 hours while travelling at approximately 80KPH. The LiDAR scanner was an essential part of the operation due to its ability to penetrate vegetation and measure ground levels. No other survey technology would have been practical to use on this scale.

A total of 5 215km was flown over 11 days to cover the 80 000ha site at 250m AGL. Keeping the sensor parallel to the terrain was a great challenge due to enormous fluctuations in SRTM elevation satellite data used for flight planning and actual ground elevations. Many geographic features were not visible in the datasets but in reality proved to be deep valleys or high ridges. This meant that at times the scanner was either too high or too low, necessitating fill in strips after data verification.

High levels of humidity, dust and airborne pollutants also impacted data collection. IT was very difficult to find 7-8 hours of data capture time without rain in a rainforest! These impediments caused a large amount of noise in the data and often gave poor penetration through wet foliage. Some tree canopies were found to be up to 80m high and ground measurements were fairly sparse in these areas.

Communications with the drone were particularly challenging as the dense jungle reduced radio broadcast power significantly. This meant that much of the flight operations were completely autonomous and special procedures were put in place for redundancy in what were BVLOS (Beyond Visual Line Of Sight) flying. Luckily the purpose-built aircraft has many of these protocols in place and was safely piloted with correct flight planning to complete the survey.

In summary, a total of 5TB of raw data was captured and processed into useful DTM and orthomosaic products in under 3 weeks. The entire project took a total of 5 weeks to achieve from commencement of fieldwork to end delivery which is in itself a major achievement for any LiDAR survey in a Jungle environment.

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