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Iron Age multivallate Durotrigian hill fort

Taken with Manta UAV and Canon IXUS 100 camera.
Synthy 99%
Views 378
Favorites 2
Photos 390
Date Created 3/9/2010

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Nathanael Over 1 year ago
I have to say... I'm very impressed! You've got nothing to be ashamed of here.

The synther couldn't correctly guess which direction was up because all the photos are looking straight down at different angles, but that's hardly an issue since the default view is practically looking straight down to begin with. You've got a great pointcloud here.

Congrats! And welcome to Photosynth.
Keep the aerials coming!

Your fellow synther,
GaryMortimer Over 1 year ago
Thanks Nathanael, next time out I will try and do some manual flying at low level that links into it then, we have another platform we could use for that, could synth cope with images taken at the same time but from another camera?? We will just try it perhaps.
TonyErnst Over 1 year ago
Like Nathanael said this shows a lot of promise. Id try angling the camera up toward the horizon a bit if possible so that the synther has an easier time figuring out which was is up
GaryMortimer Over 1 year ago
Thanks Tony, would that then mean it would flatten it as it were, better for putting down on the Bing map?? I can't fathom that bit.
Nathanael Over 1 year ago
I may be oversimplifying things, but think of Photosynth taking into consideration the way that photos are actually uploaded as a clue of which way is 'up'. It seems to me that it takes an average of the majority of the photos' 'up's to calculate the overall synth's 'up'.

When the camera is angled at closer to 45 degrees, all the photos' 'up' will have the horizon (or close to it) in common.

By contrast, when all the photos look straight down, the average 'up' will only turn out to be whichever direction you were flying when the majority of your shots were taken: i.e. North-NorthWest. That means that since the average 'up' follows the surface of the Earth, when Photosynth tries to look 'straight down' it actually ends up looking along the crust of the earth, rather than straight down at 90 degrees as it should.
Nathanael Over 1 year ago
Per your question, yes, this also holds true for geo-alignment in the site's synth editor, as it uses the vector calculated for overhead view to display the pointcloud at. It attempts to display the surface of the earth in the synth flat against your screen so that it will match the angle of the satellite imagery, but fails to correctly do so, for reasons sketched out above, in cases where all the shots look straight down.
Nathanael Over 1 year ago
When I mention the camera being at "45 degrees" above, I mean 45 degrees of either pitch or of roll up away from straight down. It needn't be 45, but I think it's a fair example.

Basically, Photosynth assumes that the photos will be uploaded "right side up" + for the majority of people that will mean walking along the surface of the earth where up is sky + down is Earth. You can stretch this somewhat with aerials, as long as you have enough shots North, South, East, West for all of the 'not quite level' shots to balance each other out, but having them all look straight down requires you to manually tell the synther what is going on + for the time being there is no such way that I'm aware of.

Something very related to your synths are KAP synths + hot air balloon synths, whose cameras are at the mercy of the wind when taking shots. Look up tbenedict here on the site to see the variation of angles that his synths incorporate without fooling overhead view.
GaryMortimer Over 1 year ago
Ah I think I see!!! I have just added some pictures with horizon in them to my quarry attempt and I also tryed to get some as I descended and then get those to link with some stood on the ground of the views. Hoping that synth will then work things out from that. I am rather afraid that I have become an instant addict, I'm not really reading all the instructions and just getting on with it!! So lets see its 700 odd images so will take a while!

A secondary effect of this playing is I am ending up with some pretty cool single vertical shots of interesting textures and shadows.

I can't get bored looking at the earth from the sky.
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