UAV: What kind of technology is tilt photography?

With the rapid development of drones, the tilt photography industry has ushered in a new wave, and more and more people use drones to engage in data collection in the surveying and mapping industry. In the process of data acquisition, various problems are encountered, which leads to the flight data not reaching the standard and the model reconstruction cannot be completed. Here, according to my own contact, I briefly sort out the parameters such as overlap, sensor, focal length, flight speed, photo interval and their relationships in the process of oblique shooting. Please correct me if there is anything wrong or wrong.

0 1 sensor

Many 3D model reconstruction softwares need to input camera sensor parameters and focal length. Usually, the input is the long dimension of the sensor.

Collect 1. 1 sensor parameters.

The sensor is a fixed parameter of the camera and has nothing to do with the drone. Although many UAVs have their own cameras, the sensor parameters are only related to the cameras. So as long as you know the camera model, you can know the sensor size. Many friends don't know how to get this parameter value, so here is the search method directly.

1. 1. 1 overview

Take Sony ar7 camera as an example. Search Sony ar7 directly,

Find a website with detailed camera parameters.

Click to enter.

Usually with sensor parameters.

1. 1.2 special case

There are also some camera manufacturers who do not explicitly give the sensor size, but generally give the type and diagonal size, which can be converted here.

Take Genie 3 of DJI UAV as an example, Baidu Genie 3, find camera parameters and sensor parameters. For the sensor, even if the size is not clearly given, it is generally the conventional size of the camera.

1.2 focal length

I don't want to say more about this. I got drunk without knowing the focal length. . . However, generally, the film without special treatment has saved the focal length parameters. You can directly right-click the image to view the properties, which records the focal length in mm in detail. Pay attention to whether the focal length parameter is 35mm equivalent focal length. Please select a value corresponding to the focal length attribute.

1.3 overlap guarantee

How to ensure overlap in aerial photography? What should the overlap be?

According to different aerial users, the degree of overlap is different. If it is only for fast image mosaic, the horizontal overlap is generally above 60%, and the routing (vertical) overlap is above 70%. If it is used for 3D reconstruction, it is suggested that the horizontal overlap is above 70% and the route (vertical) overlap is above 80%. The above values are empirical, unofficial and for reference only.

How to ensure the coincidence degree? Many flight control softwares are automatic, and the route can be automatically planned only by inputting camera parameters, flying height and overlap. So how did these routes come from? How to design the route by yourself and how to ensure that the overlap meets the requirements?

This is actually the principle of pinhole imaging learned in junior high school. Suppose the camera is perpendicular to the long-side flight direction and the route spacing is X.

According to the above conditions, the lateral overlap is calculated by the length of the sensor here.

d/ccd = h/len

Transverse overlap = x/len

It shouldn't be difficult to solve this equation, should it? X= lateral overlap *h/d*ccd

It is the same along the flight direction except for the short side size of the sensor.

1.4 flight speed and photo interval

The above process calculates the camera distance, lateral distance a and heading distance b.

What speed should it really fly? What is the photo interval? How does automatic planning software control taking photos?

In general, in order to speed up the flight and shorten the operation time, the camera has the fastest speed on the premise of ensuring the stability of the camera quality.

B= flight speed * photo interval

02 model accuracy calculation

All the above calculations are based on the specified flying altitude. How to determine the flying height? This is related to the accuracy of the model. What kind of precision model is needed and what camera is used determines the most suitable altitude for flying.

The first is the determination of photo resolution.

What's the resolution of this photo?

It is also the principle of pinhole imaging. The long-side dimension ccd of the sensor corresponds to the number of long-side pixels wx of the photographed picture. Pixel d/ccd = h/len.

Shooting resolution (m/ pixel) =ccd/d*h/w

Formula: The accuracy of oblique photography model = three times the orthographic projection score of the same project.

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FM-T 1 Tilting rotor UAV parameters (flight platform version/fuselage material: imported EPO)

wing span

1800 mm

length

1300mm

maximum take off weight

7200 grams

Maximum payload

1500g

Maximum flying altitude

5000 meters

Effective distance of digital radio station

& gt8

Effective control radius

& gt15km

Cruise speed

65-80 km/h

Continue to travel without refueling.

60-90 minutes

Difficulty of disassembly and assembly operation

Simple/1-3 minutes

Landing mode

Fully automatic vertical takeoff and landing

Cruise mode

Change from tilt cruise to fixed-wing cruise.

Maximum wind resistance

Level 5

Portable equipment

Sony a 6000/ Sony a7r/ Sony RX 1R II

Carry a camera

(Aerial Survey Edition)

Sony RX 1RII

Weight: 500 grams

Overall dimensions: 1 13.3*65.4*72mm.

Sensor size: Quan Huafu 35.9*24.0mm

Effective pixel: 42.4 million

Lens features: 35mm focal length

Aperture range: F2-F22

Continuous working time of camera: 120 minutes.

work area

8- 15 km2/sortie

machining precision

Can output1:5001:10001:2000 images/equipped with PPK post-differential module, which can reach centimeter-level accuracy after settlement.