Overview of Drone Maps & 3D Models
You may have already been collecting data for your drone maps and 3D models but feel the quality is not good enough? or you want to build on what you have already collected and improve the quality of your maps or 3D models. If so, this article will be an interesting read.
Here at Hammer Missions, we regularly test our software both in the office and in the field to help our customers improve their experience.
We believe it's not about the tool you use, it's about the workflow process you follow. So let's have a look at how to build workflows to capture & process high quality drone data!
How to measure quality?
When it comes to measuring data quality, there are several fundamentals that you should adhere to.
You can only improve on what you measure.
Having quality metrics, for example, adequate coverage of your desired area, a good GSD (Ground Sampling Distance), and site-relevant details are imperative to success.
With drone maps and 3D models, you can usually do a visual inspection for quality but this should be a qualitative approach combined with a quantitative one.
Data Capture Cheat Sheet ✨
If you are in a hurry, checkout our data capture cheat sheet which will give you a high level understanding for how to capture different types of sites and structures:
Guide To Improving Quality
So now we have discussed the fundamentals of how to measure quality we will take you through a step-by-step guide on how to action this when planning and executing your mission.
1: Follow the geometry of the structure you want to map or 3D model
Following the geometry of your structure helps reduce anomalies in your final processing and helps to concentrate on the subject that you are collecting data for.
Following the structure, especially if it is not a conventional shape, can also help reduce the time that you are in the air as you are not collecting unneeded data
In the example below you can see that we have followed the shape of the structure when planning our mission.
2: Capture Both Nadir and Oblique Shots
To ensure your 3D model is of the highest quality it is very important to collect not only nadir (top-down) but Oblique (sides) data.
Using this method you can ensure that your structure or subject is captured from all angles so your final 3D model will have no missing areas.
The example below shows how we would capture the structure using the 3D Mapping module in Hammer Missions
You will notice that we have expanded the edges of the planned mapping area outside the boundary of the structure. This is so that when the camera is in its nadir position it will capture a percentage of the facade of the building so these can be matched to the oblique data capture.
The example below demonstrates how we would capture the obliques of the structure using Hammer Missions facade mission.
With the facade mission, you are able to set a top and bottom altitude for the drone to start and stop data collection. This can be set for a single pass or multiple passes depending on the size of your structure. In the above example, we flew one pass to collect the oblique data.
For more information on facade missions please see our post below:
Step 3: Ensure High Overlap
Something to note here is that high overlap should be between all shots, not just the nadir. Ensure that both your nadir and oblique shots have at least a 70% overlap when you are collecting data.
This can easily be set up in the Hammer Missions App parameters for each mission, giving you the option to manually set the overlap whilst in planning and on the field.
💡 Note: It is very important that both the nadir and oblique overlap when planning your missions. Your oblique capture should include part of the roof and the facade for them to overlap!
You can see this in our example below where the oblique (facade) mission overlays the 3D mapping mission.
Step 4: Use Good Exposure Settings
Having the correct exposure set greatly improves the quality of your data collection and your final 3D model.
Getting the correct exposure can be tricky but we have found that taking the drone up to the height that you have designated for data collection and setting auto exposure until you are happy with how the image on the screen looks, then switching it to manual to keep those settings, works the best.
The trouble with using auto exposure is that any deviation in light, for example, a cloud moving across the sun or the angle of the sun whilst the drone is moving, will change the exposure settings if set in auto.
Another good practice would be to shoot on an overcast day, this will greatly improve any issues to may have with exposure on a bright day.
For more information on exposure settings please see our post below or have a look at our video on the subject:
Step 5: Choose a Camera with a Large Sensor Size & Megapixels
Choosing a camera with a larger sensor and Megapixel rating will also greatly improve your data collection for maps and your 3D models.
The higher the sensor size the more information will be captured.
Using a high-megapixel drone camera gives you the ability to shoot with a low GSD (Ground Sampling Distance) i.e a higher resolution at a greater distance from the structure. Shooting with a 50-megapixel camera at 190ft, for example, means that you will collect higher resolution imagery than that of a 20-megapixel camera:
For more information on GSD please see our article:
For more information on Megapixels and Camera Specifications please see our article:
Results by Hammer Missions (In-House Testing)
Below we have detailed some examples of our in-house testing here at Hammer Missions.
These tests were performed at The Mill which is where we regularly test our software.
First Method:
Originally we captured The Mill using a full nadir capture of the complete area and in this example, we also captured one side of the facade. You will notice that the nadir and oblique capture do not overlap and we do not follow the geometry of the structure.
Results:
As you can see the results are varied. Where we have captured the full nadir in an overhanging grid pattern it has rendered quite well but adding the separate facade mission at a distance has caused some issues when processing the model.
Second Method:
Now we partially use the method detailed in this post by following the geometry of the structure and adding a one-pass facade mission to cover the oblique aspect of the structure. Notice that the facade mission to capture the obliques is still not overlapping the nadir 3D Mapping mission.
Results:
As you can see from the results the render is considerably better using this method apart from the rear of the site, this was down to not enough overlap between the nadir and oblique and the fact that the nadir was set very close to the edge of the structure and did not capture any of the rear facade.
This is shown below in red
Third Method:
This would be the method discussed here in this post above.
By combining nadir and oblique, correctly overlapped we can greatly improve on the results above.
The capture below shows the nadir and oblique shots overlap each other.
Results:
The third method creates an overall better model, so combining nadir and oblique and making sure both missions overlap will give you the best results
We have recently been back to the Mill, updated our results, and created an end-to-end video showing you the whole process from planning and capturing to processing and analyzing the data.
Summary
So as we have learned from this post, it's not about the processing, it's about the capture and how important it is to plan how you are going to capture your data.
Capture is all about careful flight planning and operations planning before you venture out into the field. We hope this guide helps you understand how to improve the quality of your drone maps and 3D models.
About Us
Hammer Missions is a software platform that helps drone (UAV) teams work with versatile & high-quality drone data for site surveys and asset inspections. Our goal is to help businesses cut costs and increase ROI by building operational efficiency in their drone programs.
Hammer Hub is a cloud-based platform where drone data can be processed and visualized in a full 3D environment. This data can also be annotated using AI to accelerate the annotation process, and it can then be shared with other team members or stakeholders within the organization for further review – a great benefit when working with a digital twin.
If you haven't got a Hammer account yet and would like to try Hammer Missions you can get started with our free trial.
To find out more about using drone data for BIM and digital twins, please contact our team or visit our learning resources or take a look at our project examples.
- Team at Hammer Missions