Measuring while flying?

[Blume TMS]

I have a need to do measurements of items while flying and filming with my drones.... estimate of the average measurement I would need to take is an item say 3-8 feet away .... 2ft x 5ft and give or take 1/4" error.
It there a way... Mavic 2 Pro or Mavic Mini? Or even a different drone?

 

[bumper]

Well GPS is of no use, not with 1/4 inch resolution, or anything remotely close to that. You'd need extremely precise ranging and some sort of optical comparator. A laser based device could probably do it, not sure how drone friendly that would be.

 

[sar104]

I have a need to do measurements of items while flying and filming with my drones.... estimate of the average measurement I would need to take is an item say 3-8 feet away .... 2ft x 5ft and give or take 1/4" error.
It there a way... Mavic 2 Pro or Mavic Mini? Or even a different drone?

Disregarding the issue of doing that from the air with a drone, how would you make that kind of non-contact measurement on an object even on the ground?

 

[ratjr15]

One thing you might try if you have other, easily measurable objects in the frame for reference is an android app called Imagemeter Pro... It makes measurements based on references you set on pictures.

 

[Blume TMS]

I may look into that ratjr15... the interesting thing is there are already apps for iPhones and such that do this type of measuring with out a laser or a reference item... my older iPhone actually came with such and I have a contractor friend that has a much better one on his phone... so it seems possibly if you were using a phone with your controller and could use this type of application with the image on the screen....

 

[sar104]

I may look into that ratjr15... the interesting thing is there are already apps for iPhones and such that do this type of measuring with out a laser or a reference item... my older iPhone actually came with such and I have a contractor friend that has a much better one on his phone... so it seems possibly if you were using a phone with your controller and could use this type of application with the image on the screen....

That sounds physically impossible as stated. Calculated length of a line is a function of the subtended angle, the orientation of the line relative to the observer, and distance from the observer. The iPhone can only measure one of those three. There must be more to it.

 

[Blume TMS]

Yes I know... but here is the thing... at least with the Mavic 2 pro it has that accident avoidance thing which that and all those other items on it are looking in all directions... So it should know how far a nearby object is from it and then determining the size or specifically a length from one part to another should just be a matter of trigonometry. To put it more simply... measure the distance from the drone (assuming the drone is stationary) to the two different items and then you or actually the computer on the drone or controller should be able to determine the distance between the two items, right?

 

[Meta4]

it has that accident avoidance thing which that and all those other items on it are looking in all directions... So it should know how far a nearby object is from it.

Not with sufficient precision to be able to make your calculation with a give or take 1/4" error.

 

[Keule]

Yes I know... but here is the thing... at least with the Mavic 2 pro it has that accident avoidance thing which that and all those other items on it are looking in all directions... So it should know how far a nearby object is from it and then determining the size or specifically a length from one part to another should just be a matter of trigonometry. To put it more simply... measure the distance from the drone (assuming the drone is stationary) to the two different items and then you or actually the computer on the drone or controller should be able to determine the distance between the two items, right?

What you want to do can be done after the flight with specialized software.
You can measure distances, volumes and many more.

Here a sample output of PIX4D measuring the height of a cell tower.

 

[sar104]

What you want to do can be done after the flight with specialized software.
You can measure distances, volumes and many more.

Here a sample output of PIX4D measuring the height of a cell tower.

View attachment 100998

Any idea what the accuracy is for a 3-D reconstruction like that? I suspect that quoting to centimeter resolution is overly optimistic.

 

[Blume TMS]

I'm sure that my initial 1/4" is kind of pushing it... but thanks for the help Keule...

I was not trying and still am not trying to be argumentative, but when I hear "it can't be done" one of the voices in my head starts laughing.... for some of you young people... if anyone had told me 40 or 50 years ago we would have anything like the current drones and the technology needed to operate them I would have laughed in their face.... because it can't be done....

Example.... something like 25 years ago I started messing with and using GPS... to get the first units to work you had to tell them pretty much exactly where you were and what day and time it was and then after 5 -10 minutes the unit would give you your location within 30 meters... give or take.... I still can't figure out how a drone can usually figure out where it is exactly within a few seconds of turning it on.... not possible.

 

[Keule]

Any idea what the accuracy is for a 3-D reconstruction like that? I suspect that quoting to centimeter resolution is overly optimistic

It's depending on the GSD, the object and the quality of the images (resolution, overlap)
(PIX4D states the accuracy is usually between 1 - 3 times the GSD)

The accuracy of the cell tower was around 4 times the GSD (1.71cm/px * 4) because the object is difficult to map (flight distance and mapping path to the tower) and process due to its fine metallic structure (see-through).

Other objects are calculated very accurately. In the sample below, the width of a single solar panel was calculated by PIX4D with 1.50m. (in reality, they are 1.50m)

 

[Blume TMS]

Thanks again for that.... I'm still trying to figure out how to use that program... actually how it works and how to get it... they claim a free trial but I can't get it to run on my computer or download to my controller ... Here is what I'm actually trying to do to start.. figure out the dimensions of these two chimneys within an inch or two: