Logistic Planning for High Accuracy Survey with a Helicopter

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"Failure to Plan" is a "Plan to Fail". I have been told this all my life and it is no more evident than when you need to complete a series of LiDAR missions that are spread over a large geographic area. This article is about the planning and the execution that went into a series of eighteen projects scattered over five states along a path of over 1500 miles for the Union Pacific Railway. This project was completed under a contract with Olsson Associates of Omaha, NE and AeroMetric of Wisconsin.

The size of the crew and the required tools for the missions were carefully selected to complete the jobs in less than a week. The weather had to be considered because imagery was being acquired along with the LiDAR. The ground crew had to be trained in the client’s required safety courses then certified with three different exams that had to be passed by each employee. The projects were complicated by the fact that they were located 2200 miles from our office. In order to acquire high accuracy data for aerial mapping from a helicopter, the missions must be planned to eliminate as many systematic errors as possible and to try and account for random errors. Whether the project is a large project or a small project, the same level of care has to be taken in order to get the desired product. I am going to describe the required steps that must be taken and then put them into the context of a continuous string of small projects along a specific route. These jobs were planned and executed so a large number of projects could be completed in a small period of time.

We recently had 18 jobs to be mapped starting in California then moving to Wyoming, then Idaho, and ending by mapping across the state of Oregon. Some of these projects were relatively large and others were very small. One job was a forest project in the mountains at Truckee, CA which is west of Lake Tahoe. The other 17 projects were railway projects for the Union Pacific Railway where they were adding additional sidings or expanding existing sidings. These jobs average about five miles of corridor mapping where they wanted high density and accuracy LiDAR, color digital orthos, and planimetric mapping. Since our office is in Virginia and the projects were on the West coast, we had to take our crew across the country. The weather was analyzed to ensure that we had a block of good weather for the missions. Our helicopter was being temporarily housed in a hangar in Sacramento. We had to pick up the helicopter and do any necessary servicing before starting the project run.

Our crew flew to Sacramento and then traveled from the international airport to the Executive Airport on the south side of town to get the helicopter. We arrived around noon on Sunday after leaving the East coast at 6:00 a.m. The helicopter was serviced and ferried to Auburn. The first job was at Lake Tahoe. On Monday morning we met for breakfast and planned the day. We needed to get the helicopter up and going for the Tahoe mission. Then my surveyor and I had to drive 750 miles to Evanston, Wyoming, to be ready to fly missions there the next day. We got the base stations set up for the initialization at the Auburn Airport and left the units in clear view of the FBO. We told the FBO that our crew would pick up the units in about three hours after they finished flying the project in Tahoe, NV. We filled out the daily log for the base stations and took the necessary photos for documentation. Since there was no Primary Airport Control, we decided to get an OPUS solution for the base stations after the mission.

Once the helicopter had launched, I and my surveyor headed to Wyoming for our twelve hour drive. The helicopter flew the mission, came back to Auburn Airport and de-initialized then picked up the GPS base stations. They then headed towards Wyoming to meet us that night. My staff at the office was in contact during all of the missions. Once we knew our expected progress for the day, they would find a hotel at the town near an airport where the helicopter could land. They would then either email or send a message to tell us where to go.

Each morning at breakfast, our survey and flight crew would meet and plan the missions for the day. Since many of the areas had no cell coverage, we produced time schedules for each job to say that the surveyor must have the base stations set up on a certain control point by a definite time and this would define the time the crew would start the initialization of the system. When the crew flew the mission, they would then make a pass over the base station to let the surveyor know that the mission was complete and if possible, they would land near the railway to complete the de-initialization and the surveyor would know when they finished.

When that mission was complete that surveyor would then travel to his next project where he would occupy the control points. The flight crew would hop scotch to the next project where I would have the units set up for initialization. When we arrived at a project site, the surveyor and I would set up our base stations first thing then take photos of the stations and the site. Once that was done we would check the targets and actually place additional targets on control points that were not targeted. We had told the surveyor to place targets on the two control points on the end of each of the projects. We used local material and even the tripod cases as targets on a number of the projects.

We followed this procedure for the projects for the Union Pacific RR for four days. Each daily procedure was the same with the timing being very critical. We were about to acquire at least four projects per day and some days we got five projects. On the last day we were doing some remote projects and we got to our final project at 4 p.m. We had to decide whether to chance getting the project at 5 p.m. and have a questionable sun angle or to wait until Saturday morning to finish the missions. We made the decision to push and get the job done on Friday afternoon. If the weather was good the next morning, we could refly the imagery since the job was adjacent to the airport in Portland. The mission was completed about five thirty and we took the helicopter to the Portland Troutdale airport for the night. The next morning, the rain started and it continued for two weeks. We had completed all 18 jobs in five days, but it was only due to very tight planning and extreme execution of the proposal planning.

Not everything went as planned, but since it was planned very precisely, we were able to make minor modifications and still get the projects done. A major issue was that many of the airports along the way did not have jet fuel for our helicopter. We had to plan around the airports that did have fuel. Some listed that they had fuel and when we got there, they did not have it. We tried to stay at locations where we would be starting the next morning with full fuel and near the first project. This meant that we would travel after the last mission of the day to get to the first mission the next day.

I would take the crew to the helicopter and be sure that we had no issues with the helicopter or the mapping system and my surveyor would go to the first project. I would then go to the second project site and set up while the crew flew the first mission. We would put the control points in our moving maps in the vehicle so we could get to the area fast. Sometimes it was difficult to find access to the RR right of way because all targets were put along the tracks and their service roads.

Since we were working in the ROW and adjacent to the tracks, all of the flight crew and the survey crew had to take the safety courses and exams to be certified to work along the tracks. These on line courses are very good and once you take the tests, you receive badges to acknowledge that you have completed the course and know all the safety requirements to work along the tracks.

Bobby Tuck is a civil engineer registered as a professional engineer in four states, professional Surveyor in seven states, and a certified photogrammetrist. He is also a commercial airplane and helicopter pilot. His love for flying and surveying has resulted in the development of a mapping system that is recognized as the highest accuracy system in the world. Mr. Tuck received his BS in pre-engineering from Carson Newman College in 1973. He also received a BS civil engineering from Virginia Polytechnic Institute in 1973.