Aerial Drone Flight Logs

Aerial Drone Flight Log

Aerial Drone Flight Logs

Flight logs for your aerial drone will help you keep track of your flights, including weather, operating conditions, drone performance, and any incidents that may have legal implications. Flight logs are not mandated by the FAA, but they are recommended as a good practice to:  (1) Track your flying hours; (2) Track your drone’s flight time and flight characteristics; and (3) Document your drone’s repairs and maintenance.

What does the FAA have to say?

FAA Advisory Circular 107-2 (June 2016, canceled on 2/1/2021). Paragraph 7.3.5 states the FAA recommends recordkeeping with these words:

Small UAS owners and operators may find recordkeeping to be beneficial. This could be done by documenting any repair, modification, overhaul, or replacement of a system component resulting from normal flight operations, and recording the time-in-service for that component at the time of the maintenance procedure.

The key word is “recommended” as there is no requirement in 14 CFR Part 107 for remote pilots to keep flight logs.

What does your Insurance Company have to say?

The insurance companies that we have done business with have no requirement for pilots to keep flight logs. However, you may want to read your policy or check with your agent to be certain.

Tips for Flight Logs

FAD-Photo keeps flight logs for all of our drone flights. (We also keep copies of all flight programs, photos and videos for at least three years.) We offer these tips for developing your own flight log. Your template can be created on a word processor, with these suggested text boxes:

  • Date and time of lift-off
  • Flight time
  • Cumulative flying time
  • Battery ID, charge level at start and finish
  • Location, client, and purpose of flight
  • Flight control app
  • Max altitude, distance, and speed
  • Weather conditions
  • Flight notes, such as drone issues, photos taken, videos, flight control file names, etc.

Conclusion

Flight logs provide evidence of the number of your flight hours, number of flights, and the ability to review past flight information. Flight logs are particularly useful if you want to repeat a drone session for a client. If it’s been a while, the log will help you to locate the flight program. For example, if you need to record project progress or recapture an event, such as for insurance claims or change of seasons.

Seasonal Variations in Aerial Mapping

Summer Map, 10-acre site

Summer Contour Map, 10-acre site

Seasonal variations are an important consideration for mapping your property or structure. For summer mapping, that is the late spring to early fall, the landscape is alive with all the vibrant colors that make for great mapping photography. Although the winter months are less colorful, there are significant advantages to these maps as well.

Summer Mapping

Summer mapping is ideal for showcasing properties and structures, especially for real estate sales. Overhead maps capture the properties with beautiful colors, not to mention stunning detail. (Think of Google Maps, but with super high resolution sufficient to see small objects, such as people and animals.)

All of our map products include geoposition and altitude information, so features such as a structure’s location and height can be measured. Our map products are referenced to sea level, in units of either feet or meters. Position and altitude information are available by just clicking the desired point.

The drawback to summer mapping is that vegetation and leaves hide the landscape that lies below.

Winter Mapping

Winter mapping is ideal for topographical charting of land features otherwise masked by vegetation and leaves. Our mapping software can “see” through naked trees and capture much more of the land features otherwise obscured in summer.

Developers of properties use our topographical products to design projects and estimate their costs. The three most common map products that aid in their decision making include:

  1. Contour Maps. We develop contour lines at the interval specified by our client. They can be at any interval, such as 50 feet, 25 feet, 10 feet, etc., and any unit, such as feet or meters. We have advanced post-processing techniques that we use to overlay contour maps onto our color maps. Examples of our composite maps are shown in these summer and winter pictures.
  2. 3D Object Maps. When opened in an object viewer, these maps provide the client with a look at the property from any angle (both above and below) the image. These full-color images provide height and perspective information of landscape and structures.
  3. Point Cloud Maps. These maps provide 3D views of the map image. They appear as a cloud of points, but each point has position, altitude and color information. The real power of these maps is their ability to see landscape underneath the trees and give the project engineer detailed information on features such as mounds, river banks, small structures, etc. Any particular map section can be selected and viewed. The selection can be rotated and zoomed to view the landscape features better than an in-person survey.

For more information on precision 3D mapping, please read our June 12, 2020 blog.

Mapping Challenges

Winter Map, 10-acre site

Winter Contour Map, same 10-acre site

Our aerial drones take overhead photos shooting straight down and in rectangular patterns. At a flight altitude of 400 feet, the ground resolution is typically 1.25 inches per pixel and the resulting map size is approximately 4 megapixels per acre. OK, this is some serious resolution!

However, there are certain areas that don’t resolve well in aerial maps. Water features and non-distinct land features may be difficult to resolve because discernable points cannot be identified or they’re in motion. These challenges are minimized with high overlap photography. That is, overlapping the photos at 90%. (This means taking 18 photos per acre.) Even at high overlap settings, there still may be features that don’t resolve well, such as bodies of water.

Why? Map making software identifies overlapping pixels to determine their exact position in space. At a 90% overlap setting, a single pixel may have as many as 100 look angles, where each angle helps to establish that pixel’s exact position. Errors in calculating these angles lead to errors in the map’s presentation.

Map processing generally goes well at 90% overlap, but can degrade at lower overlap settings, wind conditions, water features, and non-distinct land features. Winter mapping is usually more challenging because land features can be drab and non-distinct.

Which Season is Right for You?

We wrote this blog to take out some of the mystery of good map making techniques. At FAD-Photo, we have developed many photo maps and know how to set up your 3D map products regardless of season.

Aerial Drone Preflight Checks

Checklist

Checklist

Preflight checks of your aerial drone are always a good idea, especially when you’re flying for a client. You may have seen a requirement from your insurance company to follow a written Standard Operating Procedure. That entails a checklist, which helps you to ensure your drone is ready for flight and to carry out its intended mission.

What does the FAA have to say?

The FAA’s position comes from the standpoint of safety of operation. Here’s the relevant sections:

14 CFR Section 107.15  Condition for safe operation:

(a) No person may operate a civil small unmanned aircraft system unless it is in a condition for safe operation. Prior to each flight, the remote pilot in command must check the small unmanned aircraft system to determine whether it is in a condition for safe operation.

(b) No person may continue flight of the small unmanned aircraft when he or she knows or has reason to know that the small unmanned aircraft system is no longer in a condition for safe operation.

FAA Advisory Circular 107-2 (June 2016, active to this date)

Para 5.9. Preflight Familiarization, Inspection, and Actions for Aircraft Operation. At 296 words, I’d rather provide you with a link than repeat it in this blog.

Para 7.3. Preflight Inspection. Ditto, 337 words, so please refer to the link.

Both paragraphs are well worth the five minutes to read.

What does your Insurance Company have to say?

Several insurance companies require aerial drone pilots to follow a Standard Operating Procedure (SOP). Although your drone manufacturer may not provide one, they’re fairly easy to develop, especially using the information in the FAA Advisory Circular.

Tips for Preflight Checks

Develop your own checklist.  We suggest including the following:

Software and firmware are up to date

SD card is installed

Camera lens is clean

Propellers are in good condition

Fresh batteries in your drone, controller, and cell phone/tablet

Develop a mission profile for your client and review prior to flight

Check the weather forecast, note the conditions prior to flight

Take off and hover at 5 feet; check propellers and flight controls

Add to this list as you see fit and go through it every time you fly. Pretty soon, your preflight checks will become second nature.

Flying Your Drone Indoors – What Could Possibly Go Wrong?

Flying Indoors

Who Is Your Insurance Company?

Flying your aerial drone inside a covered structure requires safety equipment, special settings, and a high degree of skill. This subject has been explored by a number of other bloggers, so we’ll summarize their recommendations and present a few of our own.

The FAA Does Not Have Jurisdiction over Indoor Flying

Part 107 doesn’t mention flying indoors because these areas are not considered navigable air space. However, there are a number of applications for indoor flying, including real estate photography, conventions, games, and drone competitions. Such applications require special considerations by the pilot. We’ll cover several in this article.

Insurance

When flying indoors, there’s significant risk that your drone will get damaged, harm people, and/or damage property. Therefore, check with your insurance company to see if indoor flight injuries and damages are covered.

Many drone pilots use Verify, now Thimble, a popular pay by the hour insurance company, which specifically excludes coverage for indoor flying. Our own insurance company, Global Aerospace, excludes coverage for competitions, but otherwise appears to cover indoor operations (per my agent). This gets confusing, since Thimble contracts with Global Aerospace. So, read your policy carefully to ensure you’re covered for flying indoors.

Tips for Flying Indoors

  1. Always use propeller guards to reduce injury and damage.
  2. Turn off GPS positioning. Interference or loss of signal can lead to unintended drone movements. For certain DJI drones, this means turning off P mode, and using ATTI mode instead.
  3. Related to 2, don’t use automated flight settings such as tracking or waypoints.
  4. Turn off obstacle avoidance. Although vision systems are excellent for outdoor flying, they can lead to stubborn flight control indoors and possible human error through over-reaction.
  5. Use beginner mode, if your flight controller supports it. Flight control stick sensitivities are decreased.
  6. Avoid ceilings, walls, and other flat surfaces. Prop wash causes unpredictable flight behavior.
  7. Turn off automatic Return to Home. If possible, set loss of signal action to hover in place.

For additional information, please refer to:

Drone U

Pilot Institute

Dronegenuity

Alternatives to Flying Indoors

Indoor photography can often be done just as effectively with a camera mounted onto a pole, rather than using an aerial drone. For example, mount your camera onto a glide stabilizer and walk your camera through the desired area. (We use our Samsung S20+ cell phone on a DJI Osmo for these shots.) Reduce camera shake with your video processor’s image stabilization filter.

This same technique can be used outdoors as well. A client once asked us to survey an asphalt road, suggesting that we fly just below the tree canopy. They were happy to learn of a much simpler method to mount a camera in front of and above their truck to capture their footage.

However, the cell phone/Osmo solution doesn’t work in high winds. For example, I once tried this technique from the open cockpit of a biplane but the 80 mph wind overpowered the Osmo. That approach was an epic failure, but salvaged by holding the cell phone and stabilizing the video in post processing.

When there’s no other solution than flying indoors, then we advise extreme caution, following these tips, and checking your insurance coverage.

DJI Phantom 4 Pro Yaw Drift

Phantom 4 Pro Yaw Drift

Compensate P4P Yaw Drift

What causes the Phantom 4 Pro to drift in yaw (heading) during programmed flights? This appears to be a common thread in a number of blogs and is a problem we’ve also encountered. As you know, I like to take on the hard problems, think them through and develop solutions. In this blog, I’ll offer ways to measure the offset and a method of compensation.

As I stated above, this is a common problem, but no one that I know of has determined the cause. Please comment if you have a better explanation and I’ll update this blog.

Are other aerial drones similarly affected? Please comment, I’d love to hear from you.

We See Yaw Drift in All of Our Programmed Flights

The yaw drift that we’ve encountered with our Phantom 4 Pro V2 is much more significant than crabbing (please see our April 28, 2019 blog on crabbing). Our data files indicated that the crabbing effect is around ±1.5 degrees, and is largely compensated by the drone’s flight controller. However, our measured yaw offset runs as high as 30 degrees, sometimes more.

Of note, from our data files we plotted the GPS position, which showed the drone stayed on its programmed circular path and its heading was tangent to the circle.

Measuring Yaw Offset

We program almost all of our aerial drone photography sessions, so when the drone’s camera offsets then it’s pretty obvious in the recorded video. A simple method to measure yaw drift is to record a Point of Interest video. That is, to run a circle around a point with the camera pointed at the center. A large radius allows the drone to be operated at maximum speed (we used 1000 feet radius and 21 mph in our test runs), where the drift was quite noticeable.

For example, print out a Google Map of the test site; then graph the video’s centerline of sight at 15-second intervals. You can measure the yaw offset with a ruler for distance, and a protractor for angle. E.g. measure the distance/angle from the centerline to the center point.

Graphical Data Results

Our data set included ten video runs, taken on different days so we had variations in drone speed, wind speed, and wind direction. In almost every case, the yaw drift was affected by both the drone speed and wind speed. One key measurement was the combined speed of the drone, where we found correlation between the maximum yaw drift and the combined air speed of the drone (that is, heading into the wind).

Our graphical analysis suggests that yaw drift can be minimized when both the wind speed and drone speed are less than 10 mph.

Conditions

  1. Drone: a 2-year old DJI Phantom 4 Pro V2 with an iPad 9.7-inch tablet. Yaw effects were similar for both DJI Go 4 and Litchi apps.
  2. Yaw drift appeared to be the same before and after INS and compass calibrations.
  3. We tried to force the drone’s yaw drift by hovering 5 feet above ground and blowing the drone with a fan. We blew the drone so hard that the camera’s gimbal was pushed into its stops, but it returned to linear after the wind was reduced. The drone’s airframe did tilt into the wind to maintain position, as we would expect, but it didn’t change its yaw (heading).
  4. We measured yaw drift in circular “Point of Interest” runs, where the drone’s camera was pointed toward the center and the drone airframe was flying sideways into the wind. CCW runs resulted in less yaw drift, so only one run was CW.

Conclusions

In flight, it appears that the drone’s flight controller is adjusting heading as the drone tilts into the headwind. So, if there’s a large headwind, the drone tilts more to maintain its GPS speed and it also yaws to the left. Since the drone’s legs don’t appear in the video, we conclude that the flight controller must be changing the drone’s airframe, not the camera.

Minimizing the Effects of Yaw Offset

  1. Fly your drone at a speed of less than 10 mph and when the wind is less than 10 mph.
  2. The yaw offset can be compensated by changing your programmed center point into the wind.
  3. Fly a larger diameter radius so the desired field of view is around 80% of the frame, then crop down to the desired field of view in post-processing.

Short Video Clips

Our post-production services now include short videos to dress up aerial drone video clips that we have taken. This service is ideally suited to real estate firms that want customized information added to their advertising clips.

Our full-service videos include a number of video clips and photos, introduction slides, overhead map photos, closing slides, and audio track options. The difference with our short videos is that only one selected video clip is modified to include an intro slide with agency contact information and an overhead map photo showing property information such as boundaries.

Our short videos are much easier to create and they provide our clients with tailored information in their aerial videos. This information helps your customers visualize the location of the property and area features.

Although we don’t offer moving boundary lines for our videos, we can add them to the overhead map photos (typically credited to Google Maps). Just about any text information can be added to customize the short video to our client’s requirements.

Interested? Please follow this link to a larger example of the above short video:
https://youtu.be/55B2hrF1y9k

Price information is posted to Our Prices tab, under Post-Production. Economies of scale will apply, so if you have several similar short videos in mind, we can discount our price. Please contact us for details.

Drone Take-Down Technologies

Aerial Drone Take-Down

Aerial Drone Take-Down

When small UAV pilots fly in accordance with FAA regulations, they should never have to worry about the technologies in this article. That said, a number of methods have been developed to help the military and law enforcement engage drones that are perceived as a threat. Among them are the technologies stated below. There are probably other technologies as well . . .

As mentioned in my last blog, Remote Identification of Aerial Drones, the FAA will soon require all drones in the U.S. airspace to implement new technologies that will enable identification of the drone and its owner/pilot.

Counter-Drone Technologies Include:

DroneShield offers several models that employ electronic countermeasures (radio frequency methods) to down aerial drones at ranges up to 1.25 miles.
https://www.droneshield.com/

The Dutch firm Delft Dynamics has developed an anti-drone drone called the DroneCatcher. Their medium-sized drone can lock onto a smaller UAV in the air and take it down with a net.
https://dronecatcher.nl/

A ground-based netting system has been developed by the UK firm Open Works that employs a bazooka-like gun to take down a small UAV at ranges up to 330 feet.
https://openworksengineering.com/skywall-patrol/

Lockheed-Martin developed their Athena laser-based air defense system for small targets, which can destroy small aerial drones in flight. Built for military applications, variations of this technology could find their way into domestic law enforcement.
https://www.lockheedmartin.com/en-us/products/athena.html

Drone Defense, a UK company, offers their RF-based system called the Paladyne E1000MP, which disables drone communications. Based on its description on the company’s web site, the targeted drone is kept out of a sensitive area but not taken down.
https://www.dronedefence.co.uk/

Conclusion

The popularity of aerial drones continues to grow, and with it comes the possibility of their unlawful usage. As a result, counter-drone technologies are quickly developing. For now, it seems these technologies are not available to the general public, but are almost certainly finding their way into military installations, prisons, critical infrastructure, and other controlled airspace. Small UAV pilots should be aware of them if their operations take place in or near sensitive areas.

Remote Identification of Aerial Drones

New Rule

New Rule Will Impact Small Aerial Drones

Small aerial drone technology will be changing in the next two to three years as the Federal Aviation Administration (FAA) implements new technologies that will enable tracking of drones in the U.S. airspace.

New Rule Affecting Small Aerial Drones

The FAA is currently developing a new rule that will require remote identification of small unmanned aerial systems (UAS). Upon publication of the final rule, all UAS systems flown in the U.S. will have three years to become compliant. Of note, UAS manufacturers must be compliant within two years.

Under this proposed rule, a system of unmanned air traffic management will be implemented to identify and locate aerial drones and their control stations. Information will be accessible to the FAA, national security agencies, and law enforcement. It may also be made available to the public via a cell phone application.

According to the FAA, this new system will address safety, national security, and law enforcement concerns regarding the further integration of these aircraft into the airspace while also enabling greater operational capabilities.

How Will This New Rule Be Implemented?

All UAS systems will need to be registered with the FAA. Upon take-off, the FAA envisions that the UAS will broadcast its information via RF while the remote controller will transmit information via the Internet. The FAA has specifically excluded ADS-B Out and transponder technologies due to congestion of those spectrums.

Three classes of Rule implementation are envisioned:

  1. Standard Remote Identification: Your drone will self-broadcast via RF and your remote controller will send data via an Internet connection.
  2. Limited Remote Identification: No drone RF broadcast, but the R/C must have an Internet connection. Flights will be restricted to 400 feet visual line of sight from the operator.
  3. No Remote Identification: Your drone must be operated within visual line of sight and within an FAA-recognized identification area. (The FAA will assign these areas to community-based safety organizations.)

An in-flight database is expected to include location and altitude of both the aircraft and the control station. Registered owner name will not be included at this time, but will be made available by the FAA to law enforcement. My understanding is that law enforcement will not be able to use this technology to force the aircraft down. (They have other methods to capture drones.)

Legacy Aerial Drone Systems

After this new rule phases in, operating your drone without updated remote identification capability will limit flights to within your visual line of sight and restrict your operations to an FAA-recognized identification area. Enforcement provisions don’t appear in the Rule, but the teeth may be implemented in changes to the Code of Federal Regulations.

Further information on the FAA’s proposed rule for Remote Identification of Unmanned Aircraft Systems can be found at:  Federal Register/Vol. 84, No. 250/Tuesday, December 31, 2019/Proposed Rules

Precision 3-Dimensional Mapping

Topography Map, May 2020

Topography Map Draped Over the 2-D Map

Precision 3-Dimensional Mapping

Aerial drones are the ideal method for collecting precision aerial mapping information for your land development projects. This is exciting technology and the map products that we deliver are truly breathtaking.

Each project begins with a client-provided map that outlines the site that needs to be surveyed. We enter this information into our drone’s autopilot (a mapping application), which flies the drone and collects the photos. Our typical settings are 90% overlap and 3 cm/pixel, which are further explained in our Orthomosaic Mapping and Photomapping blogs (parts 1 and 2).

We’re very good at photographing and delivering precision map products. As described below, several of these deliverables require specialized software to take full advantage of 3-D mapping. We do not offer professional cartography services, but instead provide these files to professionals who have the specialized software for these types of projects. The free software applications described below are suggested for viewing our products, but are not endorsed by FAD-Photo as suitable for professional-level mapping. We do believe, however, that many users will find them quite useful.

3-D Map Processing

Using our typical settings, the drone takes 18 photos per acre of land. For large sites, where we collect hundreds of photos, each pixel of the surface is examined at 13 or more different angles. Map processing aligns the pixels and assembles them into a 3-D composite model that includes latitude, longitude, and elevation.

Accuracy? Each photo is tagged with its position and altitude, so the composite model’s position is as accurate as the Global Positioning System. Typically, 3-4 meters.

Altitude information is based on the drone’s barometer, which has an accuracy of 3-4 meters. (We covered this specification in our April 23, 2020 blog.) Map deliverables are normalized to sea level.

Image processing is highly complex, so we use a professional mapping service provider. These are the deliverable products you will receive:

Full Color 2-Dimensional Map

This JPG file is a composite map of the photos, which are combined into a single panoramic map. Instead of a traditional scale, such as 10 meters per centimeter (or 100 feet per inch), the map service provides scale in terms of centimeters per pixel (or inches per pixel).

The JPG map doesn’t include position information, but its TIF counterpart (also a deliverable) has position information for each pixel. Use an application, such as the free QGIS software to view.

3-Dimensional Maps

DEM – Although monochrome, the Digital Elevation Model map (a TIF file) includes position and elevation information for each pixel. Special software, such as QGIS, must be used to view. The mapping service also provides a JPG of the DEM map, but this product doesn’t include position information.

Point Cloud – This is a LAS file, developed for LIDAR applications. At first glance, this full-color type of 3-D map appears fuzzy and not very useful. However, with a good viewer, such as the free Fugro Viewer, you can zoom in on the left panel image and view its corresponding 3-D model on the right panel. This is useful for looking at pixels under trees which would otherwise be masked. Of note, the 3-D model can be rotated in any direction with the mouse.

3-D Object Map – This is also a full-color map that can be rotated in any direction with the mouse. It offers a much sharper appearance than the point cloud, but it doesn’t get under the trees. Three files are required: the main 3D.OBJ file, a 3D.JPG file, and a 3D.MTL file. (You can rename the OBJ file, but don’t rename the other two.) You can open this type of map with the Windows 10 Object Viewer, but the free MeshLab viewer allows full 3-D rotation and zoom with the mouse.

Other Deliverable Map Products from FAD-Photo

The map processing report provides details on your map products, including map location, output size in pixels, scale in inches per pixel, overlap report, etc.

Topographical map (traditional contour map), where the user can specify the color scheme and contour intervals. (A postprocessing fee applies.)

Topographical map draped over the panoramic map. Here, the contour intervals are overlaid onto the full-color 2D map. An example is provided above and a larger example appears on our portfolio page. (A postprocessing fee applies.)

Do you have a special application?

Contact us for the solution. We’re experts in drone photography, mapping, and postprocessing services.

Flying Your Aerial Drone Over Water

Flying Over Water

Flying Over Water

Flying your drone at low altitude over water can be hazardous to its health. However, there are times when professional aerial drone photographers and videographers will have to do precisely that. The drones I fly are manufactured by DJI, which discourages flying over water.

DJI Manufacturer Statements Include:

The Vision System requires clear pattern variations, with light conditions greater than 100 lux. Further, they state that users should operate the aircraft with great caution when flying over water or transparent surfaces. And specifically, Vision Positioning may not function properly when the aircraft is flying over water.

What is a Vision System?

Vision systems may use ultrasonic sensors, infrared sensors, and cameras to detect objects in close proximity to the drone. Several drone models use combinations of sensors to accurately hold altitude and to enable object tracking functions.

How does a Vision System work?

Vision systems are used for short range detection and ranging. Ultrasonic-based sensors operate at about 40 kHz and use pulsed sonar techniques to detect the nearest object. Camera-based sensors employ image processing to determine objects that not only include the ground below but also people and moving vehicles.

DJI states their vision systems rely on very sophisticated image processing to detect nearby objects. Two models that I have owned are the Phantom 3 Professional and the Phantom 4 Professional Version 2. Both employ a combination of ultrasonic and camera sensors to determine their altitude above ground.

At low altitude, the fusion algorithm prioritizes the camera sensor above the ultrasonic sensor and the altimeter (barometer). e.g. the drone’s control system maintains a certain altitude that is stabilized by its downlooking camera. The problem with flying over water is that the downlooking camera sees what the human eye will see, including objects below the surface such as the bottom.

When hovering over water (or any other transparent object), the processor may be fooled into thinking the drone is flying too high, so it orders the drone to decrease its altitude. This happens fairly quickly, which risks the drone dropping into the water.

When you Absolutely Must Fly over Water . . .

If you have to fly below 2 meters for a special shot, we recommend that you turn off the Vision System to avoid unstable movements by the drone. DJI recommends that you fly the drone at low speed and stay alert to adjust altitude.

What else could possibly cause Altitude Issues over Water?

Other physical effects could fool the drone’s processor into decreasing altitude, but only one scenario seems to fit. For an ultrasonic sonar sensor, the sensitivity time control could cause a near-water second echo to be larger than the first echo, which would read a higher altitude.

What about Sonar Returns off the Sediment?

Although sound waves can penetrate the air-water interface, the transmission loss is about 99.95% – each way! Remember, the sound has to go back through the water-air interface for another loss of 99.95%. There’s just not enough signal return to fool the sensor.

You can likewise rule out other physical effects because they would lead the processor to read a lower altitude. These include: ground effect on the barometer and the increased sound speed caused by prop wash water vapor. In other words, the processor would be fooled into increasing the drone’s altitude.

Conclusion

Flying your drone at low altitude over water can risk losing your aircraft. If you must fly under these conditions, then turn off the Vision Positioning System, maintain a minimum altitude of 2 meters, and keep a close watch on your drone.