M300s H20T FOV

[MBK98]

Hi
I am wanting to calculate the H20T thermal camera (eventually all its cameras) Field of View (FOV).
I understand the FOV changes with relation to the gimbal angle and the ground, but I am wanting to know the area covered/searched at the centre of the screen (AGL). Parameters are the FL length (13.5mm) and distance AGL.

Does anyone know anything about this? Cheers

 

[Fox River Systems]

Just came upon your post from long ago. I figure I'd respond in case others have the same question. I wish that manufacturers provided specs in a way that makes it easy to get to the answer to your very common question without asking people to struggle through the math!

The H20T has a thermal sensor pixel pitch of 12 µm, sensor resolution of 640x512, and lens focal length of 13.5mm. Therefore, the sensor size is 7.68mm x 6.144mm. My trigonometry calculations for the FOV angles for the lens equates to 31.76° (horizontal) x 25.64° (vertical). Therefore, assuming the camera is pointing straight down (gimbal at -90°), the width of the scene is only a function of AGL and equates to at (0.569 x AGL) by (0.455 x AGL). So at 100m AGL with the camera pointed straight down, the field of view is 56.9 m x 45.9 m.

The surface area question you ask about is (0.569 x AGL) x (0.455 x AGL) => 0.258895 x AGL^2
At 100m AGL flight, the area = 0.258895 x 100m x 100m = 2,588.95 square meters.

Ground Sampling Distance, another important and interesting spec describing the size of area on the ground represented by 1 sensor pixel at a given AGL, can be easily derived for the H20T thermal sensor: (0.569 x AGL / 640) by (0.455 x AGL / 512). So at 100m, the Ground Sampling Distance (GSD) is 0.0889m x 0.0889m (which is also 88.9mm x 88.9mm).

I hope this is helpful!

Mike

 

[Juan Diaz]

Mike, great analysis as always. Question: how is your math behind to get to the sensor size of 7.68mm x 6.144mm?
And then to: the FOV angles for the lens equates to 31.76° (horizontal) x 25.64° (vertical)

I´m very interested in undestanding the above. Regards
JCD

 

[Fox River Systems]

Multiply the published Pixel pitch of the H20T thermal sensor (12 micrometers) by the sensor resolution of 640x512 to come up with the sensor size (in millimeters).

Then taking the focal length of 13.5mm and the sensor dimensions, you use trigonometry (arctangent function) to derive the horizontal and vertical FOV angles.

Also FYI, the published diagonal FOV (DFOV) that is equal to 40.6 degrees.

Mike

 

[phill228]

Just came upon your post from long ago. I figure I'd respond in case others have the same question. I wish that manufacturers provided specs in a way that makes it easy to get to the answer to your very common question without asking people to struggle through the math!

The H20T has a thermal sensor pixel pitch of 12 µm, sensor resolution of 640x512, and lens focal length of 13.5mm. Therefore, the sensor size is 7.68mm x 6.144mm. My trigonometry calculations for the FOV angles for the lens equates to 31.76° (horizontal) x 25.64° (vertical). Therefore, assuming the camera is pointing straight down (gimbal at -90°), the width of the scene is only a function of AGL and equates to at (0.569 x AGL) by (0.455 x AGL). So at 100m AGL with the camera pointed straight down, the field of view is 56.9 m x 45.9 m.

The surface area question you ask about is (0.569 x AGL) x (0.455 x AGL) => 0.258895 x AGL^2
At 100m AGL flight, the area = 0.258895 x 100m x 100m = 2,588.95 square meters.

Ground Sampling Distance, another important and interesting spec describing the size of area on the ground represented by 1 sensor pixel at a given AGL, can be easily derived for the H20T thermal sensor: (0.569 x AGL / 640) by (0.455 x AGL / 512). So at 100m, the Ground Sampling Distance (GSD) is 0.0889m x 0.0889m (which is also 88.9mm x 88.9mm).

I hope this is helpful!

Mike

Hey, how/where did you find the exact thermal sensor size? I'm trying to recreate your math but cannot find this info short of cracking open the H20T and measuring it. would like to avoid that at all cost haha

 

[Fox River Systems]

Hey, how/where did you find the exact thermal sensor size? I'm trying to recreate your math but cannot find this info short of cracking open the H20T and measuring it. would like to avoid that at all cost haha

Here's the math that goes into converting pixel pitch and sensor resolution (640x512) into sensor size. Multiply the pixel pitch 12um by the number of individual sensor columns: (12um x 640) = 7680um = 7.68mm. And do the same for the number of rows of sensors: 12um x 512 = 6144um = 6.144mm

Therefore sensor size is 7.68mm x 6.144mm.

Mike