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hi my name is Mike west of Mehta bunker

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dog and control science comm and in this

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video I'm going to show you how I create

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the sky distance guide that I use for

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figuring out how far away contrails are

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in photographs this is Google Earth

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which is uh I'm sure you're all familiar

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with it's very useful piece of software

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the sky here is just plain blue and if

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you had say a plane somewhere in the sky

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how would you go about figuring out how

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far away it was

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well the way I do it is I put this

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distance guide up in the sky which is

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basically a series of concentric circles

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at five mile intervals and the entire

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guy is placed in the sky at a certain

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altitude which matches the plane so if I

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know a plane's at say in this example

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it's 36,000 feet if a plane appeared

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here in an image I would know that it

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was 20 miles away from me let me just

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flip that if you'd have played here just

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above the top of the Golden Gate Bridge

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it would be 40 miles away and over here

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would be 60 miles 80 miles a hundred

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miles and if you had some plane that you

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could see way off in the distance this

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orange line here is 200 miles away and

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if I fly out of this view here you'll

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see what it actually looks like so here

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is a 200 mile radius circle with each

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individual ring being five miles further

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out and it is an altitude of about

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36,000 feet so how do we make this lets

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us go about creating it from scratch I'm

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going to delete this one that I have

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over here so what you'd need to do start

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off with is to go to the ruler tool and

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just create a line which is 200 miles

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long I just click on the way you want to

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start the line then bring it out 200

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miles it doesn't have to be exact 190

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something that you're 200 point two six

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miles

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and now I click on this like on here

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which is creating new image overlay and

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it's going to give us this and into the

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link I'm going to type in HTTP go on

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slush slush better bunk org slash rings

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dot PNG now if you don't like linking to

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meta bumble org you can just download

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this image to your computer and then you

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can link directly to the version that's

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on your computer it's just a PNG file

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it's just an image file with some

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transparency so if I press the tab

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button here just to get its load it it

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takes a few seconds and then there it is

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it's loaded it off my my web server I'm

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going to move it now so these middle of

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the the ring is at the start of the line

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that we created earlier and then I'm

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going to go out to the edge here I'm

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gonna hold down the shift key

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grab this edge and move it in so the end

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of the line is in the middle of this

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orange ring here which indicates the

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200-mile point and I click OK and get

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rid of this so now now we've got the the

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the overlay correctly sized if I go to

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the ruler tool again and go from the

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centre of the yellow dot in the middle

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to the middle of this red you'll see

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it's five files now this currently is on

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the ground if I shift it around you'll

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see it's actually conforming to the

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ground going up over those hills over

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there which isn't very useful for us

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because we want to see what the distance

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would be up in the sky so what we do is

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we go over to the imager below we've

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created click on get info which lets you

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edit it again and I'm just going to

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rename it sky doesn't guide and I'm

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going to click here on altitude and

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change it from clamp to ground to

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absolute which is going to be absolute

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relative to the sea level and I'm going

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to put in ten thousand meters you have

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to use meters for some reason press tab

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again and it will pop up the the image

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overlay to ten thousand meters which is

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about 33,000 feet click okay so now

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we've got our guide up in the sky so if

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we go down to ground level underneath

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this image overlay let's see we're down

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here somewhere go down into this park

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it's going to Street for you here but

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what we can do is click on this icon

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here to switch to ground level view and

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this will just give us the 3d building

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version of the view and you can see here

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we can see the image overlay above if we

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look straight up you'll see the dot

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directly above us

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this ring represents things that are

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five miles away when there are at 30,000

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feet

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this represents 15 at 10:15 and then 20

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miles and then they go 25 30 35 40 and

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60 80 a hundred and all the way out here

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and if you can see way off in the

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distance over here the orange line

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represents a plane that would be 200

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miles away so if you had a photograph

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taken from this particular viewpoint you

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could match up what you see from this

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viewpoint with these lines in the sky

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and if you know the altitude of the

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plane I use 33,000 Peter so general

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average for most planes that'll leave

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your contrails then you can tell how far

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away things are and it's quite easy to

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see that most contrails are going to be

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at least at least 10 miles away from you

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this this red line is 5 the Green Line

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is 10 miles away but the majority of

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contrails you see I kind of like in this

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this angle here so they're around in the

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10 to 22 to 40 60 80 miles away she's

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kind of surprising because lots people

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think of the controls as being overhead

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and when overhead is really very very

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straight up you have to be looking like

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with your head tilted all the way back

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and that's actually quite a smaller area

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when you think about it most of the area

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of the sky that you can see is a longer

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distance away in another video I'm going

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to show how to how to fit photographs to