Help needed to verify and fine tune a GSD Calculator

[Airshots.uk]

Hi fellow pilots,

I would appreciate a little help from any pilot who can spare a few minutes to help me verify and test a GSD Calculator I have built on my website;

GSD Calculator

If you find any errors or omissions either drop me an email or update this thread.

Be aware that I sourced the data needed (see below if you are adding or correcting) from a variety of sources, including asking ChatGPT to fill in the ones I struggled to find elsewhere. If any search spat out dubious or ambiguous information I simply didn't create an entry for that drone. It grew from a small handful of drones that I was personally interested in to a list of 74 drones including Autel, DJI, Dranganfly, Skydio, Trimble, Wingtra and Yuneec.

The base data needed for the calculations are as follows:

1. Sensor Width (mm)
2. Sensor Height (mm)
3. Focal Length (mm)
4. Image Width (px)
5. Image Height (px)
6. Horizontal Field of View (deg)
7. Vertical Field of View (deg)

I look forward to hearing from many of you out there and will thank you all in advance. I may be a bit tardy in responding as I am a working pilot and I'm in the UK, so time differences will apply to most of you. Many thanks,

Paul

 

[DJ Wes]

Hi fellow pilots,

I would appreciate a little help from any pilot who can spare a few minutes to help me verify and test a GSD Calculator I have built on my website;

GSD Calculator

If you find any errors or omissions either drop me an email or update this thread.

Be aware that I sourced the data needed (see below if you are adding or correcting) from a variety of sources, including asking ChatGPT to fill in the ones I struggled to find elsewhere. If any search spat out dubious or ambiguous information I simply didn't create an entry for that drone. It grew from a small handful of drones that I was personally interested in to a list of 74 drones including Autel, DJI, Dranganfly, Skydio, Trimble, Wingtra and Yuneec.

The base data needed for the calculations are as follows:

1. Sensor Width (mm)
2. Sensor Height (mm)
3. Focal Length (mm)
4. Image Width (px)
5. Image Height (px)
6. Horizontal Field of View (deg)
7. Vertical Field of View (deg)

I look forward to hearing from many of you out there and will thank you all in advance. I may be a bit tardy in responding as I am a working pilot and I'm in the UK, so time differences will apply to most of you. Many thanks,

Paul

I have spent some time gathering sensor sizes for DJI drones for use in my own GSD calculator. While there is no definitive source, I have found several different values provided for sensor size:

• Nominal (this value is sometimes advertised as the sensor size)
• Actual (this value can be computed based on the sensor area and aspect ratio)
• Active (this is the active area of the sensor which is often less than the calculated size)

While there are a number of sources, the best I have found is:

DroneModels/droneModels.json at main · Theta-Limited/DroneModels

Contribute to Theta-Limited/DroneModels development by creating an account on GitHub.

github.com

Your values for the DJI Air 2S do not match any of the values I have found for that drone. I'm curious what your source is for that drone and are you using the nominal/advertised sensor size, actual sensor size, or measured sensor size?

The dimensions you list for the DJI Air 3S imply that it captures photos with an aspect ratio of 3x2. Correct me if I am wrong, but I thought that the Air 3S captures 4x3 images. The image height you list does not match that from the DJI specs.

In your application, the flight altitude is set in feet while the calculated footprint is displayed in meters.

 

[Theta]

@DJ Wes I believe that for the air 2s, we went off the advertised (nominal) size and used a formula to approximate its actual size. We do this for certain models that we can't find much data on.

We may be wrong on the sensor size for the air 2s. The air 2 s does not output altitude metadata in any absolute reference (e.g. above msl), so it doesn't produce accurate results with OpenAthena regardless. Our camera calculation for this drone therefore might not have been very rigorous. The altitude metadata issue is common with older DJI models but is slowly being phased out.

Typically we go off the full pixel width and height of the sensor. We assume that top and bottom may be cropped by the firmware but that the width remains intact (except in photos with digital zoom applied). The Air 2s might have been an odd one with atypical 3:2 ratio.