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Photogrammetry is both an art and a complex science. When diving into this discipline, it's incredibly valuable to learn from the experiences of those who came before you—those who overcame challenges through trial and error. This blog post aims to guide you step by step through using the Elios 2 for indoor photogrammetry. While outdoor photogrammetry has its own set of considerations, indoor environments bring unique challenges like the lack of GPS and limited lighting. Whether you're new to photogrammetry or experienced in outdoor settings, this guide offers field-tested tips to help you capture high-quality images and follow the right flight path for successful results.
### Image Quality
In GPS-denied environments, image quality is everything. Here’s how to ensure your images are suitable for photogrammetry with the Elios 2:
- **Set the camera resolution to 4K**. Capturing at the highest resolution allows for better detail, and you can always downscale later if needed.
- **Maximize lighting intensity**. The lights automatically turn on at full brightness when you take off—don’t reduce them.
- **Keep the view unobstructed**. Avoid tilting the camera below -30° to prevent the cage from blocking the shot.
- **Adjust exposure correctly**. Set EV compensation to 0. If flying near walls, face them to avoid underexposure.
- **Avoid high ISO values**. High ISO increases noise, which can harm the photogrammetry process. Fly closer to objects to reduce it.
- **Limit exposure time**. Longer exposures can cause motion blur. Keep it under 1/60 if possible.
- **Fly slowly**. Faster movement leads to more blur. Minimize rotations to keep images clear.
- **Use fixed focal length**. The Elios 2 camera has a fixed focal length, which is ideal for photogrammetry.
The **Photogrammetry Flight Mode** helps automate many of these settings, including maximum LED intensity, fixed EV, reduced yaw rate, and controlled camera pitch angles.
*Data capture (left) vs 3D model (right)*
[Related read: What Is Simultaneous Localization and Mapping (SLAM)?]
### Flight Trajectory
Flying a proper trajectory is key to capturing accurate data. Consider the asset’s geometry, the area you need to cover, and the level of detail required. A good flight path demands skill and planning.
- **Explore first**. Use the first battery to survey the space, identify landmarks, and plan your route.
- **Use a grid pattern**. Flying in horizontal or vertical lines ensures consistent coverage. Look for linear features to guide your path.
- **Choose the right distance**. Closer flights increase detail (lower GSD), but be mindful of the spacing between features that help you stay aligned.
- **Maintain a constant distance**. Consistent scale improves matching in photogrammetry software. Use the Distance Lock feature to help.
- **Ensure overlap**. Aim for 50% lateral overlap to improve alignment and accuracy.
- **Maintain visual continuity**. Avoid sudden changes in scene or orientation. Overlap each image with at least 3–4 others.
- **Close the loop**. Revisit areas you've already covered to help the software correct for drift. Plan ahead to make this easier.
[Download the dataset of a brick chimney](http://bsg-i.nbxc.com/blog/8c218e453c3eb0f1b6222139ec7e96af.png)
### Train, Try, and Persevere
Indoor photogrammetry is challenging and requires skill, patience, and practice. Apply the tips outlined here, and don’t be discouraged by initial difficulties. With time, you'll become more confident in capturing high-quality datasets and creating detailed digital twins of your assets. For further learning, Pix4D has a webinar on indoor mapping.
This article is part of a series on photogrammetry:
- Why use photogrammetry to build 3D models of indoor spaces?
- Mining drones: Elios 2 creates photogrammetric models
- Building 3D models with Elios 2: how to acquire appropriate data for photogrammetry
- Building 3D models with Elios 2: processing data with a photogrammetry software
- Elios 2 Tested for Indoor Stockpile Volumetry, Produces 3D Maps Accurate to within 1 Centimeter