There are many uses for drones these days and mapping seems to be one use that is gaining popularity in many industries. Farmers are using maps of their crops to determine the health of the plants. Construction companies are using drones to capture photos of their construction sites to create maps and progress reports. Solar companies are creating thermal maps of their arrays to locate issues within the system for maintenance and repairs.
There are many different uses for orthomosaic maps and the best drone to do the job depends on quite a few factors.
DJI Phantom 4 RTK is the best drone for surveying and mapping. However, there are many other drone models out there that can also create quality orthomosaic maps.
What makes the Phantom 4 RTK the best?
The RTK system and camera quality are pretty much what put the Phantom 4 RTK ahead of the rest when it comes to mapping. There are two main reasons for this.
First, the mechanical shutter is hard to find in drone cameras in this price range, and that is what separates a good mapping drone from the best mapping drone. Next, the RTK system enables the drone to collect data that has centimeter-level accuracy, which is also hard to find in a drone at this price point.
In addition, the Phantom 4 RTK is very easy to use. Depending on which package is purchased, the drone may come ready to fly. Charge the batteries, calibrate some sensors, and away you go.
DJI makes most of its products easy to use for everyone, which means more time in the air and less time figuring out how it works. You know what they say, “time is money.”
Mechanical shutter vs. Electronic shutter
As far as mapping goes, a mechanical shutter is better than an electronic shutter. A mechanical shutter uses a moving shutter to expose the entire sensor at once, and then close it all at once. It’s much more instantaneous than with an electronic shutter, which helps keep the images from getting distorted due to motion.
With an electronic shutter, it electronically opens and closes the camera’s sensor. This type of shutter works great most of the time, but when the drone is moving and taking images, it can cause some issues.
Rolling shutter is the most common issue with electronic shutters, which happens because the electronic shutter closes the sensor one line of pixels at a time. This means that by the time the last line of the sensor is closing the subject could be in a different spot which makes the images look a little weird.
When it comes to orthomosaic mapping, a rolling shutter can cause the whole dataset to be unusable because the images will be distorted and the software will not be able to process them correctly.
Ease of use
The DJI Phantom 4 RTK is an easy-to-use drone package. DJI offers additional equipment depending on the needs of the buyer and there are different packages available online that include all the necessary equipment for successful RTK mapping missions.
The DJI D-RTK 2 mobile base station can be purchased with the Phantom 4 RTK and is a great tool to get the full RTK capabilities. This base station is easy to set up and mark your ground control points (if using any).
Once the base station, controller, and drone are all turned on, select the RTK menu on the controller screen and turn on the “Aircraft RTK Positioning” button. Then, take off and capture the data to create a very accurate and detailed orthomosaic map.
RTK (Real-Time Kinematics)
There are a few parts that make up the RTK system and they are; a base station, the drone controller, the RTK receiver (on top of the drone in this case), and satellites.
When all the parts are connected together, the accuracy of the data goes way up and the data becomes “survey grade”. This is why RTK drones are better than non-RTK drones when it comes to surveying and mapping.
The base station is an extremely important part of the RTK system and is what makes the data collected so accurate. The base station is set up and the GPS module on the base station connects to satellites, giving an accurate position of the base station. This point on the ground is what the RTK module on the drone continuously compares its position to, making the data collected by the drone so accurate.
The RTK receiver on the top of the drone is also what makes it such a good surveying and mapping drone. When the RTK module is connected to the base station, its GPS position is constantly compared to the base station so the drone’s exact location is recorded in the data collected. This typically allows accuracies of 1 centimeter which is why the data and maps created can be considered survey grade.
The controller that comes with the Phantom 4 RTK is another key component in the RTK system. The controller comes with a built-in 5.5” HD display and DJI’s Ground Station RTK flight app. The app is used to plan missions, autonomously and manually fly, and change all necessary settings in the drone and RTK system.
The inability to download and use 3rd party apps on the RTK controller is one of the few limiting factors of this drone. However, there are not many 3rd party apps available that support the Phantom 4 RTK, yet. I’m sure as it gains popularity and RTK becomes more common and affordable, applications like DroneDeploy and Pix4D will include the DJI Phantom 4 RTK on their list of supported drones.
A lot of drones use satellites for GPS positioning during flights. When the drone is connected to multiple satellites, it is able to hold its position in the air pretty well. The extreme accuracy of the data comes from when the base station is connected to GPS and the drone is connected to the base station.
Basically, the RTK system uses GPS satellites to determine the position of the drone and compares it to the position of the base station. Obviously, there’s a lot more to it than that, but that’s the basic idea.
The DJI Phantom 4 RTK can be used for other purposes, not just mapping. It has a very nice 20MP camera on it and can capture 4K video.
The DJI Phantom 4 is one of the most popular drones out there, so adding an RTK system to it makes it one of the most popular surveying and mapping drones as well.
When I’m not out collecting data for maps, I can be found doing many other drone-related activities. I don’t see any reason the Phantom 4 RTK couldn’t do any of my most common jobs for clients.
Outside of infrared inspections, my most common jobs are:
- Aerial real estate photography – This is pretty common these days and the Phantom 4 is one of the drones that takes a lot of the aerial real estate photos that you see out there. Manually flying the Phantom 4 RTK can give you the same great images as a regular Phantom 4.
- Commercial video clips – Aerial video is a great way to get someone’s attention, and the 4K capable camera can definitely handle getting some good video footage.
- 3D Modelling – The Phantom 4 RTK has a setting specifically for 3D photogrammetry in the DJI Ground Station RTK app. This makes it easy to capture the data for an accurate 3D model.
Other surveying and mapping drones
There are many different drones that are able to create pretty decent orthomosaic maps. In fact, most drones with a GPS signal and a camera on a gimbal can be used to create orthomosaic maps, but without RTK the accuracy drops significantly.
In addition to the DJI Phantom 4 RTK, there are just a few drones out there that have RTK capabilities.
What are you using it for?
If you are looking for a drone that does only mapping, then the DJI Phantom 4 RTK is probably the best choice.
However, most people that are purchasing a drone are looking for a drone that can do more than just surveying and mapping. The DJI Phantom 4 RTK can definitely do more than just mapping, and it produces great quality photos and videos.
What it can’t do is accept different payloads without some serious modification, which can be a deal-breaker for those looking for one drone that can perform many different tasks.
DJI Matrice series
The DJI Matrice 200 Series and 300 Series are also great drones for surveying and mapping. They have optional RTK receivers that can be connected to the drone to give RTK capabilities to the drone system.
The Matrice drones also have interchangeable payloads giving the option to utilize infrared cameras for thermal inspections, RGB cameras with different lenses and zoom capabilities, and LIDAR sensor options for the Matrice 300.
The reason the DJI Matrice 300 RTK is not the best is due to its price. It is significantly more expensive than the Phantom 4 RTK, but yields the same results when it comes to mapping and surveying.
The Matrice line of drones is better suited for a company that needs payload interchangeability for different types of inspections.
Cheaper RTK options
There are a couple of additional manufacturers that have drones with RTK capabilities, and come in at a lower price point than the DJI Phantom 4 RTK.
The Autel EVO 2 RTK is a foldable drone with RTK capabilities and costs much less than the Phantom 4 RTK.
However, the camera on the Autel EVO 2 RTK has an electronic shutter as opposed to the Phantom 4 RTK’s mechanical shutter. This subtle difference is what sets the Phantom 4 RTK apart from the rest of the good mapping drones.
The AEE Mach 6 is another drone that has RTK capabilities. This drone has interchangeable payloads like the DJI Matrice series and can carry multiple payloads simultaneously. It is a very capable drone and can produce Phantom 4 RTK quality maps, but is much larger than the Phantom 4 RTK.
I could not find a price listed for this drone, but I remember talking to an AEE representative last year and I believe he said it was going to be priced somewhere around the $6,000-$8,000 range, but don’t quote me on that.
As stated above, a lot of the drones that are available these days are capable of producing orthomosaic maps. The drone needs to be able to connect to GPS and have a gimbal that can be pointed straight down, or 90°.
The drone will be able to “geotag” the images with location data (metadata), which the photogrammetry software will use to stitch the images together. The accuracy of orthomosaic maps created by non-RTK drones is much lower than the accuracy of maps created by RTK enabled drones, however, the maps still look cool.
I have found a few different ratings regarding the accuracy of non-RTK orthomosaic maps, and it seems that it’s between 1-3 feet. Compared to RTK accuracies of 1-centimeter, non-RTK maps are not very accurate but can still be a valuable tool.
Lots of different industries are turning to drones and mapping these days and most do not need the extreme accuracy that RTK systems offer.
Fly what you’ve got
The best way to learn how to create orthomosaic maps with your drone is to get out there and fly. There are many different mapping apps out there, and many of them are free. The cost usually comes when you want to process the data that was collected and turn all of those images into a map.
My first maps were made using my DJI Mavic Air and a free trial of DroneDeploy. I was amazed at the outputs and instantly wanted to get out and make more maps just for fun. I have since created many maps, both RGB and infrared, and I’m still blown away by how cool the maps look every time.
Choose the right mapping app
The list of companies offering drone flight software is ever-growing, but there are a few tried and true apps available that will get you out there making maps.
- Free mission planning and flight software – DroneDeploy Flight App
- Offers a 14-day free trial to create orthomosaic maps and 3D models
- Most DJI drones are supported
- About $1,200 for “Lite” annual subscription to the processing software (price goes up from there)
- Cloud-based processing
- Free mission planning and flight software – Pix4D Capture
- Offers a 15-day free trial to create orthomosaic maps and 3D models with Pix4D Mapper
- Most DJI drones supported
- About $3,500 for Pix4D Mapper annual subscription
- Desktop processing
- Free mission planning and flight software – Map Pilot Pro
- Offers a Free Account which comes with 500 points to start creating orthomosaic maps and 3D models
- Most DJI drones supported
- Many different subscription levels that range from Free to $450/year
- Cloud-based processing
- No mission planning or flight software
- Free orthomosaic map processing application download
- Desktop processing
I recommend trying out all the different free trials you can and seeing which one works best for you.
Capturing the images can be done with whatever mapping app you prefer and you can upload the same dataset to the various different processing software and see which output works best for your applications. They are all pretty similar but there are some differences that may appeal more to certain people, so check them all out.
Issues to watch out for
There are certain things to keep in mind when choosing which processing software to go with, like can the computer handle the map processing duties, or would that be better handled by the cloud.
My old computer could not run the Pix4D Mapper application, but the new one can run that application without hesitation.
You also need to know where you’re flying and get proper authorization before you leave the office. It’s a bummer to get to the location you want to map only to have your drone not take off due to its geofencing.
There are other details to keep in mind, but I’ll explain those as we go through the next section.
Step-by-step guide to making a map with a drone (using DroneDeploy)
The process I’m about to outline is a pretty basic, beginner-friendly way to capture data and then process it into an orthomosaic map. The drone I am using for this example is the DJI Mavic Air, which is a pretty basic drone these days. I used the DroneDeploy Flight App to plan and fly the mission and then uploaded the data back at the office.
Follow these five steps and you will be able to create a great-looking orthomosaic map every time.
Required equipment – there are a few things needed to create a map:
- a drone that can connect to GPS
- a mobile device like a phone or tablet
- a DroneDeploy subscription (or other processing software)
- a computer to upload the images at the end.
For this example, a drone that is supported by the DroneDeploy Flight app is also required since I will be explaining how to create a map using DroneDeploy. Be sure to download the DroneDeploy Flight app to your mobile device before you head out into the field.
The Flight app works on both Android and IOS operating systems, so most mobile devices out there are compatible. For this example, an internet connection is also required to properly create the map boundaries.
Step 1: Mission planning
I like to do this step in the office as I find it easier to get my map outline exactly where I want it with the mouse as opposed to using the touchscreen on the iPad. The mission can be created in the field, and I actually did that for this example to get the iPad screenshots.
The planning step is one of the most critical to get right, in order to collect the correct data to create a quality map. The settings that are selected in this step will determine the flight pattern of the drone and the resolution of the map.
Anything at .5 cm/pixel or better will produce a high-resolution orthomosaic map, so keep that in mind when you’re trying to balance the speed of the flight and the quality of the output.
The first step is to open the DroneDeploy Flight app and select “new project”.
This will open a window where you can name your project. For this example, I named my project “Cemetery”, since I was mapping a cemetery near my house.
It will then prompt you to select what type of project you want to do: manual flight, standard map, façade, etc. For this example, I selected Standard to create a standard 2D orthomosaic map.
The next step is to create an outline of the area you want to map.
Select and drag the corners of the box around the area you want to map, and new points can be added to create a polygon if necessary. I drew the box around the part of the cemetery I wanted to map, and just left it “square”.
Now it’s time to start messing with the flight plan settings. I didn’t want to create a 3D model, so I turned off the enhanced 3D button. This significantly cut down on the flight time, but the 3D output will not look very good. I was not concerned with that for this mission, I just wanted a 2D map of the cemetery.
There are many different settings that can be changed to get the required images at the proper altitude. When the altitude is adjusted, the app will automatically change the speed and required image count to ensure proper overlap is achieved.
Lower altitude will give greater detail but will require more images and the drone will have to fly slower so it will take longer. Higher altitude means shorter flight time and fewer images but also less resolution.
This is where the cm/pixel measurement comes into play and the Flight app will display what the expected resolution is based on the altitude.
Next is overlap, and this is an important setting that affects the output significantly. The automatic settings are usually pretty good and will usually yield a nice-looking output. For this flight, the automatic settings were 75% front overlap and 70% side overlap.
A minimum of 60-70% overlap is required because anything less than that will not have enough matches/key points for the software to stitch the images together and the map will look warped and distorted.
The “Airspace & LAANC” button is a nice feature that makes it very easy to apply for airspace authorization if necessary. If the button is green, then you’re good to go and you don’t need to apply for an airspace authorization. If the button is orange or red then you are in either an authorization zone or a restricted zone.
When you press the LAANC button, a window will open and it will explain why authorization is required. The “Request LAANC” button will open an internet window and you can apply for LAANC authorization.
Airspace authorization is also something that I like to get before I head out into the field to fly, so I know that when I arrive, I can start to fly immediately and get the job done sooner.
There are additional settings in the DroneDeploy Flight app that can be adjusted, but for this example, the settings that are described above are all that I needed to create this map.
Step 2: Flight preparation
The most important parts of flight preparation are:
- the inspection of the intended flight path
- the pre-flight check of the aircraft
- a self-check of the pilot.
Inspect Flight Path
Even if the flight plan looks clear on the DroneDeploy Flight app I will always visually inspect the flight area before every flight to ensure there are no obstructions that the drone will contact, or even come close to contacting.
Aircraft Pre-flight Check
For the drone pre-flight check, I will inspect the propellers as I’m installing them onto the drone. Installing the propellers is also a great time to ensure the motors spin freely and there aren’t any strange noises coming from any of the motors.
I will also verify the gimbal moves freely and the landing gear is in good shape. I will then set my landing pad in an open area away from obstructions, and verify there is enough room around the landing pad in case the drone misses the pad when it’s coming back home.
Once the equipment looks good, I will turn on the controller open the DJI Go4 app and then turn on the drone. I let the gimbal do its start-up calibration and verify the controller/tablet and the drone are connected.
Once everything is connected, I calibrate the drone compass, which has to be done in the DJI Go4 app. I do this at each location I fly to ensure I get the most accurate orthomosaic map I can and make sure the drone will be able to return to home once the mission is complete.
Unfortunately, the DroneDeploy Flight app does not currently have a way to calibrate the drone compass, which is why I opened DJI GO4 first. Hopefully, they will add this in the future as it would make the calibration process faster and easier.
Now is a good time to check yourself before you wreck your drone. If you are feeling tired, stressed, or feel anything that might prevent you from completing this flight successfully, then it’s time to re-evaluate and maybe find a different time to fly.
Just because the drone battery is 100% does not mean the pilot’s battery is 100%, so be aware of your own condition. It is much better to get the job done a day late than to crash your expensive drone and possibly damage the client’s property.
Last steps to get ready to launch:
- Open the DroneDeploy Flight app
- Select the mission you want to fly.
- Verify the flight plan looks correct and the “Start preflight checklist” button is illuminated.
- Press the “Start preflight checklist” button and the app will check the airspace permissions, drone, camera, controller, and flight plan.
- Once it has successfully completed its preflight checklist, the “Start Flight” button will illuminate.
- Make sure the area is clear before pressing the “Start Flight” button because once it’s pressed the drone will take off and start its mission.
Step 3: Fly the mission
This is definitely the best part of the mapping process, in my opinion. I like watching the drone fly around by itself and collect images by itself. Just because the drone is doing all the work by itself doesn’t mean this is a time to zone out or put the controller down and take a snack break.
The drone can lose connection with the controller and may have to pause its mission, or there might be a tree that you didn’t think was in your flight path until it’s too late. The tree should have been noticed during the pre-flight checks, but maybe the mission area is not exactly where you thought it would be and a tree could be close by.
The drone will fly in a “lawnmower” pattern over the mission area, automatically taking images whenever it needs to get the proper overlap that was set in the mission planning step. Once the drone has completed the mission it will return to its takeoff point.
It will start beeping and the drone will go up to whatever the return-to-home altitude is set to. Visually verify the drone is coming back to its landing spot and clear the area. The drone will come down and land at the same spot it took off from, or at least very close, so be sure the area is free of obstructions.
Once the drone lands, the DroneDeploy Flight app will instruct you to connect the drone’s SD card to your computer to upload the images to DroneDeploy for processing.
Step 4: Post-flight checks
Once the drone has landed, perform a quick post-flight inspection. Check the propellers are still free of any damage and clean any debris off the body of the drone. Remove the battery and pack the drone and controller back into the case.
Be sure to leave the area as clean as it was when you arrived. In other words, “pack it in, pack it out”.
A laptop is something that I bring along to check the images I collected before I leave the site. Pull the SD card out of the drone, connect it to the laptop, and scroll through the images. I use 80% side overlap for a lot of my missions, so as I’m going through the images, if I see the same object in 5 consecutive images, I know I have about 80% overlap.
It’s also easy to see if there are images missing and ensure they are not blurry while checking them onsite.
I have had a drone stop taking images before, and I didn’t notice it while checking the images onsite. Once the images were uploaded to DroneDeploy it was pretty obvious that I had missed a portion of the map. I think the app didn’t upload the flight data properly after a battery change, but I’m still not really sure. I had to revisit the site and re-fly the mission. Luckily it wasn’t too far from my office, and I was able to complete another job in the area, so it worked out alright.
Step 5: Process the data
If you didn’t move the images onto your computer while onsite, do that next. Depending on the size of your map, this could take a while. The maximum number of images per map is 1,000 – 10,000 depending on which DroneDeploy subscription you have.
More images either means more detail or more area, it all depends on the parameters set during the mission planning step. For the example map I created, the drone captured 98 images and the map covers 7 acres.
Follow these steps to load up your images:
- Open the DroneDeploy dashboard and click the “New Project” button
- Press the upload button at the top of the next screen
- On the next screen enter the name of the map in the box in the upper right of the screen.
- Then either drag and drop all of the images or hit the “Select Photos” button and select the images that way.
- Be sure to include the image that was taken on the ground, right before the drone took off. This helps the processing software determine elevations more accurately.
- Press the “Upload Images” button and then the waiting begins.
Hopefully your internet connection is fast and the images are uploaded in no time. The processing time depends on the size of the map being processed, and the subscription level you have.
With the “Enterprise” subscription, your maps are moved to “the front of the line” when it comes to processing, whereas with the “Lite” subscription, the processing time takes a little bit longer but yields the same quality map in the end.
A map has been created, yay! DroneDeploy has 6 different ways to export your newly created map. PDF, GeoTIFF, JPG, Elevation, 3D Model, and Plant Health are all the different exports available, so this will cover most of your needs and are easily shareable.
The JPG is a large file, but it usually looks very nice and can be seen on all devices, which is why it is my favorite export.
Tips for succesful mapping
The top 3 tips for successful map creation vary based on the type of project, but the 3 I will outline are pretty universal.
1. Spend the time to do good mission planning
This step is definitely one of the most critical to having success while out flying and collecting data. I use this time to get acquainted with the area by studying the google map satellite images and DroneDeploy images.
Take note of trees and structures, have an idea of where you want to set up your takeoff/landing area, and verify it looks good when you get there. Be very aware of any trees that you will not be flying over and make sure the flight plan boundaries are not going to cause a collision.
I sometimes walk the perimeter of the map area to ensure there are no trees in my flight boundaries. After crashing into a tree during a mapping mission last year, I am extremely cautious now and will take a little extra time to ensure I don’t make the same mistake again.
2. Check the data before you leave the site
This step can mean the difference between making a profit and not making a profit. I have been lucky a couple of times and noticed I missed an area before I left the site. I’ve also been unlucky and had to re-fly a site before.
It only takes a few extra minutes to get the drone back up and get the images while you’re still on site. But if you leave the site and have to come back to re-fly, that’s basically working for free, and no one wants to do that.
Take the extra 10 minutes to open the laptop and plug in the SD card – it could save you money in the end.
3. Know where you’re flying
Get airspace authorization before you get to the site. It’s always a bummer to get to the site and not be able to fly the drone and complete your job. This can also cost you money so ensure you have the proper authorization and drone unlocks if necessary.
I have again, learned this lesson the hard way. Luckily, I was able to get the infrared images I needed with a handheld camera, but it took much longer and I was not able to create a map of the solar array like originally planned.
It was a strange situation with the airport being recognized on some maps and not others, but ultimately it was my fault for not having the proper unlocks, so lesson learned.
I hope this basic orthomosaic mapping how-to guide has been helpful. It is a growing market and now is definitely the time to get in. More and more companies are turning to drones to help make their processes easier and creating maps of assets is just one of the ways they are leveraging this technology.
RTK drones are definitely the most accurate mapping drones and the DJI Phantom 4 RTK seems to still be the king of surveying and mapping drones. But as shown above, even drones without RTK capabilities can create high-quality orthomosaic maps that can be used for many different purposes.
So, what are you waiting for? Get out there and start making maps.