Analysis of parameters such as overlap, sensor size and focal length in tilt photography

2020-11-19 22:42:17  作者:Tilt photography and smart3d (context capture) tutorial

With the rapid development of UAVs , Tilt photography has ushered in a new wave , More and more people use UAVs to engage in surveying and mapping industry related data collection work . In the process of data acquisition, we encountered a variety of problems , This leads to the flying data not up to standard , Unable to complete model reconstruction . Here, according to their own contact, the overlap in the process of oblique photography 、 sensor 、 The focal length 、 Speed of flight 、 Take a simple comb about the parameters such as photo interval and their relationship . Please correct if there is any mistake or mistake .

Much of this article is from 【[Smart3D Series of tutorials 2 And 《 Why is 3D reconstruction so bad ?—— Explore the neglected photographic requirements and techniques 》][Smart3D Series of tutorials 2 And _ Why is 3D reconstruction so bad _ Explore the neglected photographic requirements and techniques]】

Many 3D model reconstruction software requires input of camera sensor parameters and focal length . Generally, the input is the long side size of the sensor .

The sensor is a fixed parameter of the camera , It's not about drones , Although many UAVs have their own cameras , But the sensor parameters are only related to the camera . 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 , The search method is given directly here .

2.1.1 Routine situation

Here we use sony ar7 Camera for example .

Direct Baidu search sony ar7,

Find any website with detailed camera parameters

Come in

Usually with sensor parameters

Here you can see the long side size of the sensor 35.8mm.

2.1.2 Special cases

There are also some camera manufacturers did not give a clear sensor size , But the type and diagonal size are also given , Here we can make a conversion .

With the spirit of Dajiang UAV 3 For example .

Baidu spirit 3

Look for camera parameters

Find the sensor parameters

For sensors , Even if the size is not clearly given , But it's usually the normal size of a camera , Here is a picture from Baidu

No more than these sizes

Here you can see 1/2.3 For the sensor, the long side size is 6.16mm

2.2 The focal length

I don't want to say more about this , I don't know how much focal length I set for my photos. I'm drunk ...

But generally there is no special treatment of the film , All save the focal length parameters , You can directly right-click the image to view the properties , It records the focal length in detail , The unit is mm

Be careful , Is the focal length parameter 35mm The equivalent focal length . Please select the value corresponding to the focal length attribute .

How to ensure the overlap during aerial photography ? How much overlap should be ?

According to different aerial users , The overlap is not the same , If it's just for the sake of quick images , General lateral overlap 60% above , routes ( The longitudinal ) Overlap 70% above , If it's used for 3D reconstruction , Recommended side overlap 70% above , routes ( The longitudinal ) Overlap 80% above . The above values are empirical values , unofficial , For reference only .

How to ensure the overlap ? A lot of flight control software is automated , Just input the camera parameters , flight altitude , Overlap can automatically plan out the route . How did these routes come from ? How to design the route by yourself, how to ensure that the overlapping degree meets the requirements ?

This is actually what I learned in junior high school 【 Principle of pinhole imaging 】, Let's assume that the camera flies vertically on the long side , The distance between routes is x. And the schematic diagram is as follows :

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