Criteria for aerial photography

[chnsky77]

Hello and greetings,

for a soon-to-be realized project, I hope for some input:

We plan to digitize three parts of a small town, each around 400x400 meters. This will  be later converted to a 3D world, usable with a 3D gaming engine. When finished, players  will be able to walk and drive through those parts.

To realize this, we will have the area photographed by a professional service, which utilizes a UAV. This will hopefully be done next month, while the photogrammetry work is planned for mid next year. We can not shoot additional photos later because it is quite costly and the location is very remote.
There are a lot of businesses offering aerial photography while costs vary significantly - and it seems most of them lack the understanding what is needed for photogrammetry.

To be able to make an informed decision, we try to give those businesses detailed specifications on what we need, and here I?d like to ask for some help.

The basic settings we would like the commercial service to use when inquiring for a price:

Canon EOS5 MKII, Photos with max resolution, RAW files, 50 mm standard lens, 80% overlap on all sides.

#1 If I understand it correct, the more photos, and the lower the flight hight, the better the results.
   That means the best quality if the UAV flies at the lowest altitude possible?

#2 Is there a rule of thumb how many photos we will need / create for a 400x400m area? Or is there a tool/ software to calculate how many pictures will be shot if I enter image size, focal length, overlap, ..?

#3 Is it better to have all those photos shot from the same altitude or from the same hight over ground? The area has an elevation difference of more than 50m.

#4 Is it possible to improve the quality of the 3D model if we add additional photos (when we walk the area and) shoot from eye level?

#5 Because one part of the area has a dozen tight streets, how to best photograph them? Just flying an orthogonal raster or following the routing of the street?

#6 What angle should be used to shot the photos? Strictly either perpendicular or angular?

#7 We thought about asking to have the area photographed 4 times (always the same meandering flight pattern, but rotated by 90 degrees so we should get every object from 4 different viewpoints). Is that too much?

#8 Are there any other criteria we should focus on or ask for?



Thanks in advance,
Robert

[Wishgranter]

1. yes. lower height = better ground resolution

2. NO, exist not, its diferent from project to project, depend on many factors

3. best if  from one height, but can combine multiple heights - depend on more factors.....

4. yes, but it need proper planing to shot it from ground, but its posible

5. need to see - later on this

6.

7. depend on the scene there is not hard angles, its about the opbject what need to be "scanned"

8.


Robert, if want we can discuss it direct over my email muzeumhb@gmail.com - cangive more detailend info....

[chnsky77]

Thanks a lot, Wishgranter. I will send you an email as soon as I am back (weekend).

[ScottH]

1. Be careful with the flight height, depending on the type of UAV being used if you fly to low the camera settings MUST be set so your images do not get blurred due to the UAV speed. I fly a Gatewing X100 and have had this happen when I fly low for better resolution.

2. For an approximation of number of photos try using this website. It will give you an idea although it is a flight planning tool for the Gatewing UAV's.

 http://uas.trimble.com/calculator

Good Luck