Velocity

No. If the distance between camera and object is not known then what might seem to be a thrown baseball in the camera frame could actually be a meteor falling through the ionosphere.

Depends....

https://techcrunch.com/video/turn-your-smartphone-into-a-speed-radar-with-velocity-by-athla/

https://vimeo.com/129361441

https://itunes.apple.com/us/app/athla-velocity-hands-free-speed-radar-for-baseball/id756637522?mt=8

I suspect one must identify the moving object or sport performed. Thus one dimension, the balls diameter is known and then others dimensions can then be extrapolated.

Yes it seems if you knew the distance travelled and the frames per sec was a constant, then you would know the average speed.... but the max speed or max velocity is a little more complicated....

https://sciencing.com/calculate-maximum-velocity-6142475.html

http://www.physicsclassroom.com/class/1DKin/Lesson-1/Speed-and-Velocity

With the relatively high f stop of a cell phone camera I wouldn't trust it could tell the difference between 3 meters and 10 meters away. Two objects at those distances will be in focus at the same time.

Some cell phones are smart enough to draw a box around what it is focusing on, though perhaps not smart or fast enough to track movement. I suppose the desired accuracy might play into an app like this for a cell phone. Like using the instruments to measure room dimensions rather than a tape measure, what accuracy do you need...

Also, an instrument like this would deliver relative velocity, an interesting wrinkle

Perhaps, there is also a large market for cellphone add-on accessories that increase the capability of the phone and allow more complex apps to work (like some medical apps).

Have you tried a search of the online app stores for something?

I am skeptical too. And what about the steadiness of the measurer?

GA

Only scientific instruments ever state their uncertainty in measurement. Most people don't understand what this metric means let alone how operator error adds to this. From my observations many "scientists" don't understand this either.

Absolutely. Free-energy-devices fit this category...

Maybe not currently, but I can see the possibility of such capabilities being built into, say Galaxy 11 or 12, if a desire exists for such in a large enough volume. Shouldn't be too hard to have a laser built in for this purpose. Fairly well defined math for speed calculations from Doppler effect exist. Of course that brings up the issue of a laser in a class room, which is currently frowned on, and what teen is going to want a phone he/she can't take to school, or the possibility of a phone taking down a plane by blinding the pilots. Well.....maybe not.

So that leaves us with what is in there now, and I don't see the LED light being all that effective, except under ideal conditions. The camera use has been already discussed by others.

Thanks for replying to my inquiry. Based on your response, do you think a phone app could be developed for speed calculations using Doppler?

Yes, but it requires a much better source for a reflected signal than that LED in the phones. I already expressed the concerns with a laser, and that would certainly discourage Samsung, Apple, and all from trying it. I've never seen any company try to miniaturize a true radar, but maybe I've missed that. Such an endeavor by any company would require a perceived large desire for such capabilities.

Thanks again. When I drive within approximately 100' from a school zone, the sign at the side of the road immediately displays my current speed in MPH. I am assuming that it uses doppler technology. Do you have any idea how I might find out if doppler technology can be miniaturized and used in a phone app? Just as the phone uses a point and click feature and immediate display on the phone screen, I am hopeful that the same feature could be applied to determine and display speed using a phone app. Any feedback is appreciated. Thanks. BGeorge

I think those signs use ultrasonic sound as the signal to be reflected, similar to a so called "radar level sensor", which is in fact ultrasonics at work. We would need to be very careful with that in a phone or we'd drive our 4 legged friends crazy if we used this near them. However that might be easier to miniaturize and probably lower energy required to run it.

Side note - anyone ever notice if dogs/cats/rats/bats avoid the areas where these signs are located?

I just say that this is possible - not that I could do it. Those signs are a good example of this technology, just not small enough. Obviously it is not too expensive, because a lot of small towns have these speed signs now.

Do you know a person or business that I could contact about working with me to develop a phone app using radar or other technology with "point and click" capability to determine and display velocity? If not, do you have any thoughts/ideas on how I might get to that next step? Thanks.

Sorry - no. I am a controls engineer (I work with industrial process instruments daily - these are rather large) with advanced studies in physics many years ago, so the way to do it is obvious. The ultrasonic level detectors we use present a means that would be just dandy as a relatively benign source of a signal for reflectance and analysis, (much safer than a laser) but who can actually do it??????

Thanks again.

I see how it, " could " work . I will rely on the engineers to tell me if this is possible. Here goes :

It will require two phones. Each phone has a compass app. The first phone's compass app is on, this means that the phone is receiving data from an orbiting gps satellite- so, a coordinate position is known ( charted ) .

The second phone's app for compass is on too and it is receiving a coordinate. Let's say there is 1 mile separation between each phone.

Each phone's camera is on. As the object passes in front of phone 1 , a time is recorded, when the object passes in front of phone 2, a time is recorded.

Phone 1 & phone 2 must be in contact with each other.

The distance between each phone could be an arbitrary number.

Based on the time stamp between phone 1 & 2 a calculation could be performed to determine speed and velocity.

This is my thought of how such a measurement could be ascertained.

Now I will leave it up to the engineers to show an example of the equation.

Use 2 or more lenses with collimator slots in front of the lenses.The image could be broken into segments as it appears in each slot,and the timing measured as it travels from slot to slot. You stated you wanted to determine the velocity of an object passing in front of the phone. The distance to the object or size will still be required.