3Dsurvey mission: mobile photogrammetry development
For several decades, our cities around the globe have been getting bigger, more complex, more populated, and smarter, and so is the infrastructure.
In this fast-growing tempo, government and local authorities are struggling with collecting the data in order to keep city planning and infrastructure changes under control.
Surveying is for sure one of the most important services that help tackle this challenge. And it does so with the help of photogrammetry. It provides proper data, which can later be processed and calculated to avoid all the possible issues.
How could we collect this kind of city planning data with photogrammetry?
One of the options is through a traditional approach. Traditional measurement (GNSS, tape, stick) is accurate, but very time consuming to gather. By the time you measure and draw the plan, there is a new crossroad already built across the street and what you have done becomes outdated. Moving forward, we would have two options:
We could collect the data through a terrestrial photogrammetry process or with a mobile laser scanner. However, prices for that option start around 50,000€ and that’s steep for a small land surveying company. Therefore we had to find a more affordable and faster mapping solution for urban areas and critical infrastructure.
The other idea was lidar scanning. This is used in various ways, such as with helicopters, aircraft, drones and also terrestrial and mobile. The latter are often used for mapping roads, because there’s an interest in digitising traffic and municipal infrastructure and detecting damage and anomalies. But are you allowed to fly in the city centre? Probably not. Therefore, in the case of lidar vs photogrammetry, photogrammetry was clearly the winner.
So how should we acquire the data accurately, easily and fast with minimum effort? There were a lot of options on the plate, unfortunately all of them are expensive or prohibited by law. 3Dsurvey, however, is all about simple (and more affordable) solutions. So we went out and started our own mission. This is a short story about our development of a mobile photogrammetry solution.
1. First steps towards our mobile photogrammetry solution
As we have been developing photogrammetry software solutions for more than a decade, we believe we have acquired a lot of knowledge about drone photogrammetry. Being pragmatic and assuming that if it works with drones, it will also work with a car… We tested it out!
The idea was to acquire images with telemetry and the easiest way was to do so was to use an RTK drone. So, we mounted a Phantom 4 RTK with three additional digital cameras (2x Blackmagic cameras with 7Artisans fisheye lens & 1x Sony camera) along with an Insta360 One R Twin Edition sports camera on the car roof. The cameras were connected to displays and the car power outlet. Before we started, we set the cameras to 1 second rounds and turned on the drones.
We drove down the road and took pictures with drones and cameras. Then we downloaded the images to the computer and processed them with the 3Dsurvey surveying software and the results were incredible. Truly!
From the video and processed data it looks like a really easy job, but in fact, we had several iterations of this and we were trying out all sorts of possible combinations of shutter speed, camera angles and driving speed. We also had a lot of challenges with synchronising the data between cameras and positioning devices. We also had some issues when collecting the data on the fly and with the accuracy of the data acquired.
There was some deep learning involved. But as you can see from the pictures, we managed to create a prototype that really works!
2. Results of our study and next steps
We now knew exactly what photogrammetry hardware we needed, how to set up the hardware configuration, synchronise devices, what the best shutter and location settings were and how fast we could drive. The question that was left open though was: do we really want to compete as a hardware vendor on the market? Do we want to deal with photogrammetry hardware production and distribution? The answer was NO. We are the (best) surveying software guys.
3. Those who seek (photogrammetry hardware) will eventually find… in Hungary
Therefore, we made the next step to search for companies that are using a similar approach and are already manufacturing these devices. We found a young enthusiastic Hungarian team, InterMap, who had developed a similar device. No questions asked, we drove to Budapest to find out the details of their offering.
Their device, the GeoMeter, is simple and efficient. It consists of a robust and durable construction, 2 high resolution cameras, INS module and 2 GPS antennas with RTK receiver, a high-performance black box and controller. Great job, Hungary!
4. The road tests and results
As we are surveyors, we are always allergic to results that are not accurate, and of slow measurement processes, as we want everything fast, accurate and simple!
Using the GeoMeter for a day, we measured and tested that:
- The horizontal positional accuracy of the test point cloud was on average 10 cm compared to validation points
- The vertical positional accuracy of the test point cloud was on average 12 cm compared to the validation points.
- The validation points were measured at the beginning and at the end of the measurements.
- Better accuracy of up to 4 cm is required, which we were able to achieve by setting ground control points every 200 m on each side of the road.
Using the GeoMeter for collecting information about municipal infrastructure and detecting damage and anomalies, is simply perfect. The device was exactly what we wanted with excellent support from their development team. We were driving around Budapest, testing the device and only after 48 hours decided that we wanted to make it a part of our mobile mapping solution.
The final result of our mobile photogrammetry mission
Below, you can see the point cloud made by the mobile photogrammetric device and how interesting it is.
We surveyors always strive for accurate data. Accuracy and precision are the most important to us. With the GeoMeter we achieved quite good results. The horizontal positional accuracy of the test point cloud was on average 10 cm and the vertical 12 cm compared to the validation points. The validation points were measured at the beginning and at the end of the measurements.
GeoMeter is perfect photogrammetry hardware for collecting information about municipal infrastructure and detecting damage and anomalies and with 3Dsurvey photogrammetry software, it’s a perfect combination! For land survey maps, a higher accuracy of up to 4 cm is required, which we were able to achieve by setting ground control points every 200 m on each side of the road and some other tweaks (we will talk about them in one of our future blogs so stay in touch).
For more info on the GeoMeter: https://www.intermap.hu/en/geometer
Interested in checking out our webinar about the GeoMeter? Watch it below.