Sky High

I need some help from some really experienced pilots. How high would you say I was in the image that looks the highest in the thread below? I found a good way to judge altitude without an altimeter is by standing in one end zone of a football field and hovering in the other. That's a known distance of 300 ft. which is a great ruler or yardstick! So, I get a good reference as to the size (scale) of my helo at that distance. Then, when directly overhead, I can judge my altitude by how big my helo is in the sky.

www.rcuniverse.com/forum/fb.asp?m=3812072

kd7ost

I can't tell. It depends on your camera and the FOV as well as the angle it was shot at too. What camera and what size sensor? Are you sure it wasn't zoomed in any? 250 to 300 feet for me is right after take off or starting out on my downwing leg. At any rate you were most likely under 500 feet. There are instruments out there you can put on your platform that remove the doubt and debate. Using a camera picture to judge distance is pretty scientific. You need to know the FOV, the angle an oblique is shot at and the measurements of the most distance points on the ground that are in your picture. Different camera's shooting at the same FOV will also be different. You need to make sure to test the camera with measured references for accurate data. Without those numbers it's a grab bag. Obliques always look higher than true verticals. That's the way the human eye/brain connection works. I wouldn't be too worried about it unless you get too low.

Dan

Sky High

Thanks for that technical info, but, what's the highest you think I was judging by the images or video, dammit?

kd7ost

Nice attitude brainiac.

I think you were flying off the surface of Mars. You must be high anyway.

Maybe you should try to educate yourself a little and come back when you can talk to adults like an adult.
I can still help you out and give you a direction to start. I was ignorant once too.

http://www.rsr.org/sighting_pole.html

Dan

Sky High

LMAO!!! [sm=lol.gif]Hey, I resemble those remarks! How many adults do you know that fly R/C? None, we're all big kids. Now, what do you think that smiley face was for? That was a friendly dammit......DAMMIT! As I stated, I appreciated all of that info but I just need a pro, like yourself, to give me a good estimate of my highest altitude. Thanks for the link, that was mighty Dan of ya!

The Ignorant One

kd7ost

Perhaps you didn't read all the words in my first post about the infomation needed to do that. (Frankly you're seeming a little obsessed about it for some reason) I don't know if you were zoomed in or out. Do you understand that? What was your lens set at? 28mm, 32mm, 46mm etc? It throws off the numbers and becomes something I have to pull out of my.... What was the angle you shot it at. Same thing. FOV is needed otherwise I can sit here and tell you with certaintly that I'm pretty sure all of that was between 0 ft agl and 600 ft agl. Anything more dialed in than that becomes pure speculation. What are the distances between reference points out there.

You might as well be asking me how much I think you weigh based on your post. I don't have the information needed. (Probably between 0 and 400 pounds) You'll have to settle for that. You have the best idea how high you were because you saw all the pieces.

What's your real question or reason for asking? You seem to be holding somthing back. You must be "Sky High"!

Dan

Sky High

Well, I have been estimating since I've been flying and finally used the trick with the football field described above. I had a conversation with someone in another forum that seemed to think that I was not nearly as high as I thought so I explained to them that I have always estimated, like most do, since I don't have an altimeter until I discovered and used the stadium method with the scale of the helo to the known 300 ft distance. So, I wanted to hear other more experienced pilots' opinions to see how far off I was. I think at the highest point I was at least at 200 ft. I'm going to find out how tall the stadium lights are at our other baseball stadium because they are tall as hell and I have easily cleared them before.

kd7ost

Well it sounds like you have a plan in place. Sorry I can't help you tell the other guy he's wrong. I'm one of those guys that has seen enough and been surprized about being wrong (when I swore I was right) that I've learned no amount of, "Hey what do you think about this....." is going to hold up in a court of law. You throw night lighting etc into it and human perception can whack so far out that you really need to discount it if you're trying to prove something. You can get yourself some facts and then come back and tell that guy he was wrong. (But you can't tell me that) Simply because I didn't commit to a speculation.

Good luck

Dan

Sky High

I don't know that he's wrong but I also don't know that he's right either. He didn't say that he was using an altimeter when comparing his aerial image of his estimated 130 ft that was similar in FOV as mine.

kd7ost

You know, not to kick a dead horse but certain visual perception can go way out of whack at certain times. Let’s use a comfortable example. The Harvest Moon. It sits low on the horizon and looks like its moved half of its normal distance away. I mean it's huge and just hanging there. (Only when it's low on the horizon though) You see it at night with normal skyline around and the human thinks the moon is fricken huge. It's not. It's the same size as always. You perceive it as being bigger in reference to the skyline and things you're familiar with seeing. Your brain is doing comparison with what it sees and what you’re memories are and tricking the heck out of you. Next time you see a harvest moon, turn away and bend over. Look at the moon from between your legs. This will effectively make the normally familiar looking horizon, become un-familiar. The moon will instantly look normal sized to you.

This doesn’t directly explain what could be going on and I’m not trying to suggest you’re wrong. But at night, with many normal visual cues gone from site, things look differently. Coupled with anxiety and a heightened sense of nerves your brain can make you see things in a way that they really aren’t. No one is lying. They see what they see. But it could easily be a Harvest Moon.

Dan

Sky High

I think I will just take a picure of that scene and invert it. Otherwise, I'll have some explaining to do if I try the physical method out in public. Interesting though.

Sky High

I have definitely experienced some depth perception problems while flying causing near misses with poles that have almost been fatal. I have flown towards a pole with the helo 90 degrees or parallel to me and thought I was going to pass on the opposite side of the pole, when in fact, I flew by on the side closest to me. That is a strange sensation because your mind expects the helo to briefly disappear behind the pole but instead it is visible the whole time and then it hits you that you probably just had a near miss only a feet or a few inches from that pole. [X(] This is also true with altitude when flying near poles or structures. I grazed the top of a light pole thinking that I was at least 10 ft above it from the angle that I was viewing it and the helo, very misleading. [X(] I had flown through the goal posts at the stadium many times before from a head on orientation with no issues but a while back I was at a profle and finally struck one of the uprights because I miscalculated the distance of the center of the uprights and vertical pole closest to me because of depth perception and well, you know what happened. [:'(]

kd7ost

Lets throw the exercise the other direction.

How high do you think I was when I took this picture?

Dan

A10FLYR

My Feedback: (1)

I'll bet you didn't clear 200'.... We almost always think we are higher than we really are. You would NEVER catch me flying a chopper above the light poles at nite! My depth perception really sucks.

Sky High

Dan, I'd say.......pretty damn high!! [sm=lol.gif] Well, without a reference like a car or building, I would say at least 2000 ft.

kd7ost

And this is in daylight, although there lacks many familiar clues.

Dan

twinturbostang

SkyHigh: Alright, I'll give you a number. In the highest pics, I'm guestimating 150 to 200 feet. There. Now go prove me wrong by installing some telemetry on your heli.

Sky High

That was during the day when I brushed that pole, but I do it at night too, as with these demo videos were speaking of. I usually only fly near structures or poles when I know for sure that I'm well above them but with that incident I was climbing out and thought I was higher than I was because of the my angle of view.

A10FLYR

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Dan,
Between 400' and 500'?

bdavison

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Around 300ft max for the staples parking lot.

Here's the po'folks altimeter....
http://www.glide.dyndns.org/on-the-w...tude_scale.pdf

12 - 14,000ft roughly for the cropcircles pic...hard to tell as there are no architectural elements except the road.

kd7ost

Hey Dean,

I got your 1000 post. Cool

Your estimate is about correct but it was a trick question. Reason is, I'm not positive how high I was. I would estimate about double what you guessed. I'm using a Fuji finepix E510 which has an effective lens of 28mm. That's about double the FOV of most little digital cameras. It makes it look like I'm twice the altitude of say a Canon SD450 at wide angle. (Just an example. The Canon only has a 32mm lens when not zoomed) But on top of it all, I cropped the picture so it's not even all there. That makes it look closer than I really was.

I was just trying to illustrate to Sky High that there are a lot of variables that need to be known in order to accurately guess an altitude from a picture. It's easy to be way off yet think you are correct.

Dan

kd7ost

This actually brings to mind a game or contest. It might be hard to do though.

You have to know what altitude you took the picture from either from GPS or BP source. Something accurate say within 50 to 100 feet.
Then post the picture with what FOV or mm lens used. There would need to be enough reference points on the ground for someone to measure the size. You can't scale or crop or anything like that, Then let folks try to figure out the altitude the picture was shot from. I don't have any pictures that I know exactly what altitude agl I was at though. There might not be too many of those around.

Dan

A10FLYR

My Feedback: (1)

Oh Man! How dissapointing!!! I just knew you had an overlay that would shoot us all down!

Wait!!! 1000th post = 1000'

I just got off Google Earth and couldn't find the crop circles around Nampa in Yer pic but I was in a hurry. I'll bet they were in Washington.

As for judging from a pic.....AMEN! You never know for sure and any guess would be just that....a guess.

Eddie Weeks had a turbinized DC-10, hugh bird, at Florida Jets a few years back. We all guessed he was 1000' to 1500' feet up. Altimeter watch in the plane said he never got above 500'! Of course we don't know what pressure variation was in the fuse during flight to throw the watch off.

A10FLYR

My Feedback: (1)

Thanks!!! I'd forgotten all about that from somewhere in my distance past! I can't remember where but I've seen that. I'll give it a try.

bdavison

My Feedback: (1)

Altitude is all tricky... Altitude can be measured in AGL, or At sea level....

If the road in the cropcircles pic is a 2 lane rd, Id say it was 3600ft...but it looks like a big interstate (4lanes or something) in which case I'll stick with my 12,14K