Case Study:

AERIAL PHOTOGRAMMETRY

 

Traditionally, mapping has been accomplished with LiDAR systems flown on fixed wing aircraft. Now, we can provide the same level of accuracy from a sUAS platform using aerial photogrammetry.


sUAS (small unmanned aerial systems) outfitted with Photogrammetry or LiDAR survey equipment offer a more efficent and cost saving alternative to manned aircraft (planes or helicopters). Using these technologies on an unmanned platform can also yield more accurate results, see our examples below. sUAS is most effective on smaller scale projects, where the ease of unmanned systems really shine.

What is Aerial Photogrammetry?

Aerial Photogrammetry is the process of taking hundreds, or even thousands, of pictures and stitching them together to create a 3D orthomosaic of a specific area.  Though many people disregard this method for mapping… its results can be just as accurate, if not more so than LiDAR.

Why Unmanned?

In the growing world of drones, there is one major proponent that is hard to ignore – they are simple. Manned aircraft add layers of complexity that are unavoidable. This includes heavy maintenance schedules, refueling on the job, access to airports, noise in urban areas, etc. Now compare these examples to an advanced drone system, which require a simple battery change, take off and landing from virtually anywhere, and easily flown in urban and rural settings alike.

But the major reason that clients are switching to unmanned systems is for liability and insurance. No longer are aircraft required to have a physical pilot, much less a second camera operator. These tasks can be done from the ground while monitoring and accessing live video feeds of the mapping progress.

Gather Data – Simple or Complex

Flight Evolved has the unique ability to fly both high resolution Photogrammetry and LiDAR systems. This gives us the perfect combination of equipment for any project, big or small. Both systems have their pros and cons, and that’s why having both is a necessity. Photogrammetry is starting to show a rise in popularity as soon as the drone industry took off. This new ability to fly high resolution cameras unmanned is a major turning point for photogrammetry.

Photogrammetry is perfect for anything 3D. The results don’t necessarily end with a point cloud. Textured mesh can bring to life these high density point clouds and provide incredible promotional material.  The point clouds are generally much more dense, so they require much more processing power and storage space for this increased demand.

The major upgrade in Photogrammetry today versing years past is that it can now provide distinctive measurement, rather than just telling a story. The results have survey grade accuracy, entirely measurable, and can be imported into any 3D or CAD software. This means you can measure distances, calculate volumes, and check angles.

That being said, LiDAR is still the reigning champ for anything that encompasses large areas or heavy vegetation/tree cover. The major pit for Photogrammetry is being limited to what the camera can see. LiDAR can penetrate tree cover and vegetation to provide topographical maps of the bare earth. LiDAR is also unaffected by very static environments like snow or water. Photogrammetry relies on high contrast to create unique tie points, and in situations like snow, can be difficult.

Example 1 – Oblique, Dynamic Environments

Below is an example of a very complex mapping situation. The area of focus was Blodgett Canyon outside of Hamilton, Montana. Blodgett Canyon is an incredibly oblique and dynamic setting, with cliff walls extending upwards of 1,000 feet. These are some of the largest cliffs in our country outside of Yosemite. This was the perfect setting to test the limits of our equipment.

The mouth of Blodgett Canyon, as seen from the road.

The goal of this study was to test the accuracy of not just the topographical map, but the formation and detail of the cliff in a 3D model. There is no surprise in creating a basic topo map, but to recreate an overly vertical cliff wall would be a true testament of our process. We used our Photogrammetry setup so we could recreate this scene in a 3D model and test the accuracy of Photogrammetry in a very oblique setting.

Results

The results were amazing. The cliff was fully recreated and displayed attributes that were hard to see with the naked eye sitting there at the trailhead.

Basic topographical map of the mouth of the canyon

Example 2 – Static Open Fields

It would seem intuitive that if we can do something as dynamic as Blodgett Canyon, then simple open fields should be no big deal. That does seem logical, but for our study we wanted to test something that had very little elevation differences.

In mapping, simple is not always “simple.” Simple can imply little contrast changes and similar objects across the map. When this happens, the software has a harder time distinguishing between different features because of their similarity. This used to be a problem just a few years back with older, lower resolutions cameras. These problems are much more rare now with our higher quality imagery.

The field we mapped is 20 acres, but only has around 15ft of elevation change in the upper field. It then drops off on the west side to a water ditch and lower field. This study showcases the sensitivity of this technology and its ability to be used in all different settings, complex or not.

Results

This example shows the high accuracy of Photogrammetry. Just a few years ago, only LiDAR could have accomplished this. Not only are we extracting incredible terrain results, but have the ability to render a 3D model and orthomosaic in RGB colored format. This is something we can’t replicate with LiDAR.

 

Google Earth image of the field

Sample image from our Photogrammetry sequence

Topographical map in 1 foot intervals

DSM (Digital Surface Model)

3D Orthomosaic

 

Conclusion

By using sUAS platforms, we can save our client time, money, and make the process much more efficient.  Our turnaround time is typically just a few days, with data acquisition being completed in as little as a few hours.

If you are interested in learning more about our topographical and 3D mapping, feel free to contact us with any questions you might have.