Drone mapping is a complex art.
Not only do you need to be familiar with proper mapping procedures like geographic information systems (GIS) but you need to be an expert drone pilot who knows how to fly and plan for a mapping mission.
In this article, we’ll go over the top mistakes that beginner drone pilots make in their first mapping jobs.
Let’s get started.
Table of Contents
1. Not Understanding Different Types of Accuracy
Accuracy is crucial for any drone map. After all, what’s a map worth if you can’t accurately measure distances with it?
But there’s more to mapping accuracy than just flying straight. You have to use the right equipment and calibrate their settings correctly.
To get started, you should know the three different types of mapping accuracy:
Relative Accuracy
Relative accuracy, aka local accuracy, means that the map is proportional with itself. Any two points on the map are accurately distanced relative to any other points.
This type of accuracy is only useful so long as you don’t need to measure distances in the real world.
Absolute Accuracy
To measure real distances, you need to aim for absolute accuracy. Also known as global accuracy, absolute accuracy corresponds to actual GPS coordinates, including latitude, longitude, and height. You need this level of precision for construction projects, land titles, and environmental surveys, for example.
To achieve absolute accuracy, you’ll need to lay out geotagged checkpoints called ground control points (GCPs). GCPs are large markers, often in the form of an X, that you place strategically at points around the survey site. Because they have a known geographic location, you can align them with the drone footage in post-processing to get a margin of error within only 0.1 feet (0.03 m).
Survey-grade Accuracy
Lastly, survey-grade accuracy is a term used to describe the highest level of accuracy in the industry. Also known as GIS-grade accuracy, it has no official definition, though it must hold up in court and generally refers to an accuracy of within 4 inches (10 cm). Such surveys are required for land-title, as-built, and other types of land surveys.
To reach this level of accuracy, you need to follow American Society of Photogrammetry and Remote Sensing (ASPRS) guidelines and be a licensed surveyor. Of course, you’ll also need survey-grade equipment, including several GCPs, which brings us to our next mistake.
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A Proven Roadmap of Success for Implementing Drones in Construction.
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2. Not Using Ground Control Points (GCPs)
Many beginner drone pilots don’t realize they need GCPs to create geographically accurate maps. On top of that, your maps won’t turn out right if you don’t layout the GCPs properly. For example, you need to make sure to place them around the perimeter of the survey site. Otherwise, you may warp the edges of the map because they aren’t geotagged.
Video Credit: Propeller Aero
After you place a GCP, you need to record it’s GPS position. To be safe, measure each GCP location twice. Once before flight and once after. That way, you can correct for any discrepancies if the GCPs happened to get moved during the project.
“If we’re going to make a critical determination off of the data set, absolutely we’re going to use GCPs.
- Hunter Cole, Brasfield & Gorrie
3. Incorrect Front and Side Overlap
When it comes to drone mapping, the more overlapping footage you have, the better. Then your mapping software has more reference points to work with.
Post-processing photogrammetry software locates thousands of common points between images called keypoints. When keypoints on two different images match, the software can generate a 3D point. If there aren’t enough overlapping keypoints, mapping software won’t have enough data to stitch together an accurate map.
There are two different types of drone mapping overlap you need to know: front and side overlap. Front overlap is the amount of overlap from one image to the next, while side overlap is the amount of overlap between each leg of a flight. For best results, you want to have at least 80% front overlap and 75% side overlap so you have a lot of data to work with.
You also want to extend your flight boundaries at least 100 feet beyond the site you’re interested in mapping. That way, you’re sure not to miss anything.
4. Flying with Inconsistent Lighting
Lighting conditions greatly impact the quality of your map as well. If the light varies during the flight, it could cause your drone photos to have different exposures.
For example, partly cloudy days can cause the sunlight to vary significantly around the survey site, which could leave you with imbalanced data and an uneven map.
So check the weather forecast before you perform a mapping survey and avoid partly cloudy or sunny days when possible. Its best to aim for a full overcast where the lighting is consistent and the clouds act as a light diffuser so no harsh shadows are present on the map.
5. Not Using Real-time Kinematic Positioning (RTK)
Real-time kinematic positioning (RTK) is an advanced GPS technology that corrects drone positioning mid-flight. An RTK base sends GPS data directly to the drone so you can ensure the aircraft stays on course as it goes.
RTK allows the drone to fly within a 1 inch (3 cm) margin of error, which will in turn greatly improve the accuracy of your mapping data. In essence, RTK corrects for positional errors before they happen, so you have less to correct in post-processing. Combined with powerful mapping software, RTK makes your drone maps much easier and precise.
Stop Making these Drone Mapping Mistakes
Well, now you know the top things to avoid when drone mapping! You’re already ahead of many beginner drone surveyors. But that doesn’t necessarily mean you’re ready to produce quality maps. Drone mapping is not a beginner drone pilot job. It takes a licensed pilot with the right training and experience.
That’s why many companies outsource their drone mapping needs to The Drone Life. We pride ourselves on delivering high-quality and accurate maps that are achieved in a fraction of the time compared to traditional survey methods.
If you need professional drone mapping services, feel free to schedule a free consultation with one of our drone experts today.
What's included in YOUR GUIDE...
A Proven Roadmap of Success for Implementing Drones in Construction.
A List of Red Flags to Avoid When Hiring Drone Service Providers.
How to Persuade Your Leadership Team to Leverage Drones on Every Jobsite.
