Time to Replace Your Drone’s Batteries

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Battery Performance

Battery Performance Over Time

Our research indicates that aerial drone batteries need to be replaced every two to four years. This article will explain our reasoning, which may serve as guidance for your operations. For reference, we fly DJI Mavic and Phantom drones, but other drones that use Lithium Polymer technology will have similar performance characteristics.

Do You Trust Everything You Read on the Internet?

So, I go online and the first page or so of Google Search hits tell me that my DJI drone battery will last up to 30 minutes, can take 200 to 400 charge cycles, and last around two years. Well, that hasn’t quite been our experience, so we’re going to present some information that may more accurately reflect the performance you can expect.

Data From Our Flight Logs Paints a Different Picture

First of all, our flight operations are almost all commercial, primarily supporting the real estate sales and housing development markets. So, our batteries are often required to support flights at altitudes of 400 feet and speeds of 32 mph. This is a bit more demanding than flying at low altitudes and slow speeds. Thus, we shouldn’t expect our batteries to last 30 minutes. So, what should we expect?

We keep log sheets for all of our drone flights, where four years of data shows us:

1.  Our average flight times are 18 minutes.

2.  Our average battery usage ranges from 96% at beginning to 26% at end (70% diff.).

3.  For an average battery usage of 70%, we get about 3.9% per minute. (This is the same as 0.26 minutes per %, just invert.)

This information alone is probably worth your time to read to this point. However, it gets more interesting when the data is examined.

Graphing the Data Reveals Insight into When Your Batteries Need Replacement

The above graph shows that over time your batteries lose their ability to hold a charge. (Our measure of performance is flight time divided by percent battery usage). Microsoft Excel’s trend line tells us the battery’s capacity is around 0.28 minutes per percent (min/%) for a new Phantom 4 Intelligent Flight Battery. At four years, the battery’s capacity has decreased to around 0.23 min/%. This decay appears linearly related to time (not frequency of use) and for the Phantom 4 battery it indicates a 20% loss at four years.

Note the graph shows a 14-month period of no data – but the slope continued linearly indicating it’s the battery chemistry, not usage, that was driving the decay of capacity.

Key takeaway: Your typical 70% flight on day one will last about 20 minutes, and four years later will last about 16 minutes. (There are a number of factors that also contribute to battery performance including deep discharge cycles, damage from crashes, temperatures, etc.)

Mavic 2 batteries had similar graphs and similar flight times, with one important difference. The slope of their decay line was about twice that of the Phantom 4 batteries. The data analysis showed Mavic 2 batteries decay to 80% capacity at around their two-year point.

How does this Information Compare to Performance Specs on the Internet?

We believe this information is complementary to DJI’s performance spec. If you pop your drone up ten feet and let it idle, a new battery may last 30 minutes. But in more demanding situations (read real-world usage), we believe our data more closely represents your experience.

Our commercial flights have been spread across a number of batteries, so each one has a limited number of discharge cycles (less than 100). If you’re usage is significantly higher, then your batteries may lose their ability to hold a full charge at the 300-500 cycle mark, whenever that may occur. According to DJI, that may occur at its two-year mark.

Conclusions

Battery performance depends on its chemistry, which decays over time. We have shown that our Phantom 4 batteries decayed to their 80% capacity point at four years.

Data also shows our Mavic 2 batteries were at their 80% capacity point at two years. We suspect DJI traded off capacity for performance, probably by recalibrating their battery chemistry.

In addition, an aging battery gives off gases, which causes its case to swell. When your battery swells to the point that it requires effort to insert/remove from your drone, this also indicates it’s time to replace. In our experience, our Phantom 4 batteries were sufficiently swollen to warrant replacement at 4 years. Coincidentally, at their 80% point.

3D Mapping Limitations

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Mapping Failure

Failure to Resolve Shrubs and Trees

Three-Dimensional (3D) mapping with an aerial drone is exciting technology, but certain types of terrain will limit’s its usefulness. We’ll explain why some map jobs turn out good, others not so well.

Terrain Features that are Difficult to Resolve

In addition to our mapping service’s recommendation for photo set collection, we’ve found that terrain can be a significant limiting factor in the success of a mapping mission. Namely, shrubs and trees.

Many of our clients prefer terrain maps in the winter when the leaves are down so we can get ground-level elevation information. However, when the ground is covered with shrubs and trees the map doesn’t resolve very well. This is because the vegetation is too complex for the 3D processor. Remember, it’s trying to triangulate each pixel to assign its point in space. We’ve seen this even with overlaps as high as 90%/90%.

Notice the forested areas that don’t resolve well in this photo. You can see the trees have unfocused swirl artifacts. In more challenging areas, the map processor gives up and leaves the area blank. Although this picture came from our mapping service (which uses high-powered image processing), our panorama software PT Gui Pro also failed to resolve.

Other terrains such as developed properties have enough order to their colors, shades, and textures, that the map processor can triangulate the pixels. We’ve had excellent results mapping buildings, developed land, and roads.

What does our Mapping Service Recommend?

Our service includes these requirements for the photo set:

• Minimize areas with surface water

• Use an overlap of 75%/75% or better (we use 85 to 90%)

• Minimize windy conditions and long shadows

• Fly mapping missions at least 1.5 hours off solar noon

• The drone’s altitude should be at least 4 times the height of the tallest feature

However, our mapping service doesn’t have a specification for forested areas. We’ve talked about this, and they only go so far as to admit that these areas can be “challenging.”

Conclusion

We guarantee our map results and will not charge for results that our clients can’t use. However, mapping forested areas is risky for us so we may decline jobs like this. We’ll view your proposed map site with Google Maps and advise if it’s worthwhile to fly a mapping mission.

Altimeter Error’s Effect on 3D Mapping

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Aerial Drone Altimeter Error

Aerial Drone Altimeter Error

One of the specifications you won’t find for your aerial drone is its altitude accuracy. In fact, if you call the manufacturer’s support team, they probably won’t provide you with that spec. So, what do you tell a client when their mapping accuracy requirement is critical?

At FAD-Photo, we have calculated what you can expect in terms of altitude accuracy and can show you how this altitude error affects 3D mapping.

Your drone’s altimeter takes its readings from an internal barometer, does the conversions, and writes them to the photo tags, which are used by the mapping service. Mapping service providers will tell you that their numerical processing is accurate, but subject to the altitude information provided by the drone. But what if the drone’s altitude data is drifting over the duration of the mapping session?

The map processing service assumes the drone flies its mapping session in a perfectly flat plane. If the drone’s altitude readings shift during flight, then its plane shifts. This in turn shifts the ground plane causing terrain elevations to shift.

How does an Altimeter Work?

This blog is an update to our April 2020 blog Aerial Drone Altimeter Accuracy Specification. We analyzed nine months of data to refine our opinion on altimeter accuracy.

As one goes up in altitude, the air pressure goes down. The relationship between air pressure and altitude is quite predictable. So, using the formula below the altitude is easily converted from the drone’s internal air pressure sensor (a miniature barometer):

A = -(RT/gM)*ln(Po/P)

Where A is the drone’s altitude (height difference between the measurement altitude and the starting altitude), R is the gas constant, T is temperature of the air, g is the acceleration due to gravity, M is the molar mass of air, Po is the atmospheric pressure at the starting altitude, and P is the atmospheric pressure at the drone’s measurement altitude.

This formula is coded into the drone’s software so the barometer’s pressure reading can be converted to altitude. The constants R, g and M do not change, but the variables Po and P do change and are used in the calculation. The temperature T is assumed to be constant, but in reality, it’s affected by the temperature of the drone’s barometer and thus contributes to altitude error.

Over the course of a flight session, not only does the drone’s internal barometer sense pressure but it also senses the temperature effects of ambient air and heat dissipation of the internal components.

What Does the Data Tell us?

Our Flight Logs provided the record of end-of-flight altitudes for flights longer than 10 minutes. The resulting graph appears above.

The data indicate that altitude error is positive during the cooler months and negative during the warmer months. We know that average seasonal temperatures follow a sinusoidal curve, starting about 46 days after the autumn equinox (or 55 days before 1/1). Also, temperature variations are dependent on region, weather patterns, and time of day. In our case, this data was taken in central Virginia.

Developing a Trend Line

Using MS Excel’s Solver add-in, we derived the sine wave “trend line”, which follows this formula:

Altitude Error (trend line) = 2.44 + 4.74*sin((Date + 70.2)/365)

The resulting curve represents the altitude error in feet that may be expected throughout the year. The average offset is 2.44 ft plus a sinusoidal component with a peak value of 4.74 ft. The date offset of 70.2 days was expected to be closer to 55 days but is at least in the ballpark. As we collect more data, these numbers should become more accurate.

Statistical Data Calculated from the Trend Line

Other statistical data were calculated from the trend line minus the landing altitude data. We calculated a Standard Deviation of 4.60 ft and a Margin of Error of 1.14 ft (for a confidence interval of 95%). We then stacked these errors, so the expected altitude error at end of flight (EOF) is:

Altitude Error (EOF) = 2.44 +/-4.74 +/-4.60 +/-1.14 ft

Which ranges from 12.93 to -8.04 ft throughout the year

Since the drone altitude at takeoff is zero, we know this error has to build up over the course of a flight. Approximating this buildup as linear, the midpoint error is about half of the EOF altitude error:

Altitude Error (midpoint): ranges from 6.47 to -4.02 ft throughout the year

This means that for a 20-minute mapping session, the altitude error specification is around +/-6.5 ft. That is, the error can start off at zero and end at 13 ft, about a mean of 6.5 ft. The graph shows that the worst-case error can be slightly higher, but in most cases is somewhat less.

Conclusions

We take our maximum calculated error of +/-6.5 ft and round up to +/-7 ft, which we use as our altitude specification. Altitude inaccuracies affect topography mapping because our mapping service takes altimeter readings from the photo tags and cannot compensate for these errors.

For topography maps, contour lines at 10-ft intervals approach the useful limits of this technology. We can generate 5-ft contours (or less), but the overall mapping information becomes less and less useful. However, contour lines on this order may still be useful for assessing localized areas, such as slopes and structures.

Altitude error will be reduced for shorter duration mapping sessions and (as seen on the graph) near the sine wave crossings in late May and late September.

So, why won’t your drone manufacturer tell you its altimeter specification? Well, it’s complicated . . .

Remote Identification of Aerial Drones, Part 2

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Remote Identification

Coming Soon to Law Enforcement Near You

The aerial drone community is more abuzz than usual with the new FAA rule on UAS Remote Identification. The final rule was published in the Federal Register on March 10 and becomes effective on April 21, 2021. This article updates our July 20, 2020 blog on Remote ID.

Compliance deadlines: September 16, 2022 for manufacturers and September 16, 2023 for operators.

Purpose:

The purpose of Remote identification is to require aerial drones to broadcast their identification and location information. This will help the FAA, law enforcement, and other federal agencies to find the control station when a drone appears to be flying in an unsafe manner or when it enters a location where it’s not allowed to fly.

The FAA’s overview is published at: UAS Remote Identification Overview

The full rule is published at: Federal Register :: Remote Identification of Unmanned Aircraft

How Do I Meet The New Requirements?

There are three ways for drone pilots to meet the new requirements:

(1) Your drone is classified as a Standard Remote ID Drone. That is, your drone was produced with built-in Remote ID broadcast capability, which includes identification and control station location. See the section below to find out if your drone is already compliant.

(2) Your drone has been fitted with a Remote ID broadcast module, which broadcasts identification and take-off location. Many present aerial drone systems fall into this category.

(3) Your drone won’t need to comply with this new rule. The FAA will only allow the drone to be lawfully operated at FAA-recognized identification areas, which are sponsored by community-based organizations or educational institutions.

What’s All This Broadcast Business?

Remote ID broadcast messages will include:

  • A unique identifier for the drone
  • The drone’s lat/lon, altitude, and velocity
  • The control station’s (or take-off location’s) lat/lon and altitude
  • Time mark
  • Emergency status (standard drones only, see (1) above)

FAA Registration

Presently, small aerial drones are registered at the FAA’s web site “Drone Zone.” This date, I don’t see a section for Remote ID Registration, but expect this will be the place for it.

Many Aerial Drones Are Already Compliant With Remote ID

In anticipation of the FAA’s new rule, some drone manufacturers have already programmed Remote ID into their software. At FAD-Photo, our Mavic 2 Pro and Phantom 4 Pro V2 drones are compliant (or nearly compliant). DJI’s control program, Go 4, has fields to enter Remote ID information, but there’s a question as to whether they’re fully compliant. If not, then we expect the remedy will be a software update.

 Check to see if your drone is on the compliant list at Drone U’s web site.

Additional Information

Read what drone manufacturer DJI has to say about Remote Identification at this DroneLife link.

Conclusion

Now that Remote Identification is the law of the land (well, the USA at least) it’s time to start thinking about our compliance deadline of September 16, 2023.

Aerial Drone Flight Logs

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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

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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.

DJI Phantom 4 Pro Yaw Drift

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Phantom 4 Pro Yaw Drift

Compensate P4P Yaw Drift

What causes the Phantom 4 Pro to drift in yaw (heading) during programmed flights, such as Orbit Mode? 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.

Use an Alternative to Orbit Mode

Program your drone with waypoints, enable curves, and place a Point of Interest in the center. With a little practice you can capture a beautiful “orbit” that doesn’t suffer the effects of yaw drift. This has become our preferred method of flying circular patterns.

Short Video Clips

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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.

Remote Identification of Aerial Drones

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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

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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?

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