Aerial Photogrammetry & LiDAR – Which Technology Should You Choose?
For accurate mapping and land surveying, the two leading technologies used are aerial photogrammetry and LiDAR. How do these methods differ, what are their advantages and disadvantages, and above all, which one should you choose for your next project? We are breaking down the two technologies to help you decide which option is right for you.
What Is Aerial Photogrammetry?
Photogrammetry uses images to measure distance and create detailed maps. While the technology dates back to 1840, almost concurrent with the initial invention of photography. However, the methods used in aerial photogrammetry are much more modern.
A drone is equipped with a camera pointed down toward the earth and is flown along a specific automated flight path while the camera captures overlapping photos of the terrain below. When you look at an individual photo, you’ll see that there’s a center point where all that is visible is the very top of that point, whether it’s a building or a tree. There’s no added dimension visible. However, the buildings, vegetation, and structures around the center point appear to be leaning toward the center. This is what’s called relief displacement, and the further a building or object is from that center point, the more relief displacement is visible. This alone is not enough to create an accurate topographic map, which is why overlapping images captured from different angles is necessary to achieve parallax.
Parallax is the apparent shift in positions of features when you see it from different angles. By combining the angles in the images and looking at the structures from different points of observation, you can measure the relief displacement which then allows you to generate a high resolution 3D map that goes beyond elevations and also includes textures, shapes, and colors.
Advantages and Disadvantages of Aerial Photogrammetry
Now that we know what photogrammetry is, let’s look at the pros and cons of using this method to create maps and survey land.
Benefits of Aerial Photogrammetry
- Accurate to the real world to include colors and textures in a highly detailed map;
- High horizontal accuracy;
- Easy to interpret and analyze;
Drawbacks of Aerial Photogrammetry
- Images can not penetrate vegetation like LiDAR;
- Not quite as in-depth to include complex structure modeling, 3D modeling of cables or power lines;
- Very large data sizes for orthomosaics;
What Is LiDAR
While we’ve discussed LiDAR technology at length, let’s look at it in comparison to photogrammetry. LiDAR stands for light detection and ranging and has been around since the mid-1970s. However, drone technology has allowed it to expand in usage.
UAV LiDAR involves a drone flying over a set area while a sensor sends out laser pulses at a rate of 100k-3million pulses per second onto the earth and measures the time it takes for the signal to return. A highly precise satellite positioning system is used to determine the exact location of the sensors and by combining location with measuring the time and intensity of how the pulses return, a data analyst can use direct georeferencing to extract the data and turn it into a highly detailed point file or map.
Advantages and Disadvantages of LiDAR Technology
With the basics of LiDAR down, let’s consider the advantages and disadvantages.
Benefits of LiDAR Technology
- Highly accurate detailing in a topographical map or 3D model;
- Outputs can be colorized based on how intense the reflection is, making it easier to see the difference between soft objects like leaves and hard objects like buildings;
- Can be used in dense vegetation to get accurate measurements of forest floors as the lasers make it through the areas in between leaves and grass;
- Can quickly scan thousands of acres;
- Provides massive datasets;
Drawbacks of LiDAR Technology
- Can be cost-prohibitive for small areas;
- Accuracy is affected by fog and rain;
- Will not penetrate water;
Using a Combination of Photogrammetry & LiDAR
In some cases, a project may call for both LiDAR and photogrammetry. You can colorize a LiDAR point file with photogrammetry. It provides colorized pixel values to each corresponding LiDAR point allowing for the end-user to perform more accurate feature extraction.
Contact Us for Photogrammetry & LiDAR Services!
Photogrammetry and LiDAR both are used to create 3D modeling that is changing how we see the world. If you are looking for a highly accurate and incredibly detailed topographic map that includes power lines and complex structures, we would recommend you consider LiDAR with FlyGuys. Not only do we have an experienced team of professional, certified drone pilots, we offer cost-effective pricing to get you the information you need. Contact us today for a free consultation or quote at 1-888-376-6965 or fill out the contact form below.
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