Making 3D site surveys as accurate as possible is a top priority for any surveyor. Besides ensuring proper ground control during flight, one way to do that is to edit your terrain to get rid of obstructions and other inaccuracies.
For surveyors and others onsite, it’s essential to have total control over survey data and the ability to customize visual and data outputs. This is because editing your terrain means you can customize your site model and get more accurate measurements. Without this feature, many are reluctant to adopt a drone surveying software.
So what can terrain editing do for you? Let’s take a look at four ways you can use Propeller’s terrain editing to improve your 3D site models.
1. Edit your surveys with both terrain filtering and editing
Editing terrain means you can precisely refine your terrain models, as necessary. But that’s a manual process. Pairing it with a terrain filter can help with many of the features you’re looking to eliminate.
Propeller has a number of filtering options that work for different things, from removing vegetation to buildings. For example, you can choose a lighter filter, such as the equipment filter, and then manually remove anything left behind after the filter has been applied.
“Propeller’s Smart Filtering does some of the heavy lifting when it comes to removing features and objects like equipment, vegetation, and buildings,” Smith explains of the whole terrain filtering process. “But if you choose to use the strongest filter it can remove things you don’t want it to.”
Smith recommends a dual process of using a filter targeting equipment and refining more with terrain editing as needed. “For anyone doing earthwork, I recommend they still use the Equipment filter because it does a really good job of removing inaccuracies and features in a time-efficient way,” he explains. “Once you’ve done it, you can then go in and further refine your model.”
This two-part process gives both the confidence in and control of your data that you need, which is especially important when sharing data with other team members, project managers, or higher-ups at your company.
“You can be confident you’re sharing good and consistent data, while still maintaining control during that part of the process,” Smith said.
2. Quickly remove stockpiles and features for more accurate volumes
No matter what kind of earthwork site you’re on, you probably have stockpiles at some point during the job. Sometimes it’s necessary to remove stockpiles from a surface to get more accurate calculations depending on what information you need.
Instead of looking at the many scenarios of editing stockpiles, let’s take a look at how doing so helps you better calculate month-to-month volumes on a landfill.
Part of standard operating procedure for any landfill is to cover the cell each day with a layer of dirt. But that can make for inaccurate volumes later. “While every effort is made to push the layer of dirt off before work starts again the following day, the extra layers of material added to cells lead to inaccurate monthly for progress reporting,” noted Smith.
Typically, fixing this issue means measuring the volume of the stockpile used for cover dirt, entering it into a spreadsheet, and manually subtracting it from the total end-of-month volume.
But this can be cumbersome. Being able to directly edit terrain—to quickly draw around the stockpile and edit it out of the model instantly—makes finding that final monthly number easier than ever. “This simple process saves time and leads to more accurate quantities, which means monthly reports you can trust,” noted Smith.
3. Clean up areas that don’t look quite right
One of the biggest advantages to 3D drone data site surveys is their rich, visual nature. But this also means that any “weird-looking” parts of the model (usually artifacts of the photogrammetry process) can stick out like a sore thumb, even when they don’t affect any measurements.
While these areas vary from site to site, one of the biggest sources of these blips are bodies of water. Water is notoriously hard to map by photogrammetry because of its constantly changing surface and how it reflects light.
These qualities cause big changes between individual photos in a dataset. Those differences result in unavoidable peaks and troughs in the surface. But by editing this part of your terrain, you can flatten the feature to make it better match the actual surface. It’s as easy as creating a boundary with a couple of clicks.
Such edits are purely for cosmetic purposes, but they do improve the perception of the overall model.
Especially when working with someone unfamiliar with photogrammetry, editing out problem areas like bodies of water “help improve the perception of how trustworthy your survey data is,” said Smith. “Anyone who sees waves 10ft tall and deep troughs will often mistrust what they are looking at and it can raise questions around the accuracy of the data.”
4. Remove vegetation affecting volumes
Similarly to removing bodies of water for visual purposes, another great use of terrain editing is removing trees or vegetated. But in this case it’s because they’re affecting volume measurements.
That’s just what happened to Smith during a test flight recently. He did one flight at 80m and again at 50m. “The flights were done straight after each other and processed separately,” Smith remembered. “The ground surface was really consistent across both surveys, but when I came to calculate the volume of the area, there was huge variation between the two.”
After investigating the cause, he found it was because of nearby trees. Why? “Trees move in the wind, and this change between the two surveys caused large discrepancy in the calculated volume,” Smith explained. “You can edit the terrain to completely flatten the area of trees on both surveys to generate a more accurate measurement.”
Smith shared a final tip for using terrain editing to improve your 3D site surveys: “If you are removing something and want to compare like for like then you need to make changes to both surveys.”