Plan for Success
Few job design actions are vitally important as planning data acquisition. As procurements increase in size and sophistication so does the involvement of the numbers of stakeholders and their requirements. It is essential to guarantee the acquisition procedure considers all potential requirements. This can be critical because budgets and schedules preclude re-flying a job if a company overlooks a planning factor. Some planning elements are generally understood, such as national airspace deconfliction, calm winds, or high sun for photogrammetry overlays. However other planning factors may not be germane.
Seasonal Demands. Specific environments and products demand leaf-on states where vegetation is at its vigorous condition, many mapping applications call for optimum exposure of man-made and terrain attributes (leaf-off vegetation, no snow, and natural rivers height). When adding weather as a consideration, specific areas may present the proper conditions for only a couple of weeks annually.
Time of Day or Time of Occurrence. For urban mapping products, if imagery feature extraction is required to overlay the lidar, then picking a time of day with a minimum pattern of life, such as a street free of parked cars, may be required to allow collection of manholes, street markings, and other attributes. For Coastal Erosion and Beach mapping, tidal height timing will be necessary.
Air Space (National and Local). Depending on where you are, national airspace may require coordination, such as conducting collection at night after the last flight. The advantage of using drones is in some cases drones can operate under airspace restrictions that general aviation may not be able to access. Finally, one last point, if you do have to submit for airspace authorization, it is best to provide for three to four different dates to allow for weather and re-work. The process is improving, but in some cases, it was taking 90 to 120 days to get national airspace clearance.
Frequency Deconfliction and Geo Correction Stations. While current regulation limits the range, a drone can fly from its operator, the advantage UAVs have is they can fly close to terrain and human attributes. Within less than five years we can expect drones to be flying for miles like they do in other parts of the world. However, regardless of distance, a drone requires a telemetry and control tether to control flight operations, allow for aircraft deconfliction, and allow real-time geo-correction services. For this the selection and effectiveness of the radios and modems being used are essential. In urban environments tend to be “noisy” meaning the signal needs to compete with other similar signals such as house wifi, utility remote reporting infrastructure, and other FCC approved uses of the bandwidth. Further buildings can obscure or shorten controlling distances. In mountain conditions being so low to the earth, the terrain may mask signals preventing monitoring and corrective services. In both cases, picking right control areas is vital to successful operations.
Sensor Selection. Lidar is an incredible tool, but it only tells part of the story. Depending on your customer’s needs you may also need color information integrated into your data. Photogrammetry has its limitation, seeing under obstructions, for collecting bare earth and small vertical objects. In some applications, it is the color of the surface features that typically is what is desired. This leads you to multi-sensor acquisition operations.
Here there is a tradeoff for many drone service providers who have limited options for focal length selection or some waveforms and emitters. Drone service providers have two options. First, they can use shorter focal length lens and slower Megapixel sensors of inexpensive cameras. This will require the drone to fly lower than what is optimum for LiDAR collection and will need more cornrows or Swaths. This increases in the field collection time and in office processing times. The other option is to pick a lens/sensor option that will complement the altitude and field of view of the LiDAR sensor.
If you are bidding on a project, we recommend running both sets of numbers. First with the cost of your current equipment and factoring in the increased collection/processing times. Then conduct the same estimations with the more expensive sensors and times. Finally, decide if you want to buy or rent the equipment for the job. These options are better-clarified upfront in a bid or project kickoff than apologized after collection.
Everyone knows that using drones over most manual methods of collection produce a ten-time advantage. However, as drones become the norm in traditional industries the need to be efficient and bid competitively will be paramount. Not considering collection times, site operation locations, and optimum equipment could lead to collection time overruns and loss of critical profit margin to acquire better gear. Adding drones to business does not change how business is done, just how it is delivered, and not delivering efficiently can negatively impact reputation and future work.
If you are preparing a bid or considering using LiDAR in your business, consider consulting with about these planning factors. For a Free 20 minute consultation click here.
Drone LiDAR Accuracy White Paper
We just completed a 3 LiDAR sensor grant study for CalTrans and California State University Fresno to produce an accuracy comparison white paper and the California DOT Drone Aerial LiDAR Standards.
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