Messages

121

General / Re: Optimization generates heavy noise in sparse cloud

« on: August 19, 2014, 11:29:50 AM »

Import after optimization to do what ?
Is it possible to use georeferenced markers to georeference WITHOUT optimization ?

122

General / Re: Optimization generates heavy noise in sparse cloud

« on: August 18, 2014, 10:38:31 PM »

I will try your suggestion.
But doing this way, the cloud will be misoriented, and I will loose georeferencing ?

123

General / Re: Developing RAW to JPEG

« on: August 17, 2014, 09:45:04 PM »

I'm using Photoshop CS5 with Canon's Camera Raw plugin.
Works fine and batch processing is very easy to manage.
Be sure not to use any image distorsion removal functionality. Phortogrammetry will not appreciate.
Dont crop or reorient images.
In the same mood, avoid applying too much image sharpening, because it can modify local values.
Colour balancing and contrast stretching are OK

124

General / Re: Best buy camera and lens?

« on: August 17, 2014, 08:03:02 PM »

The lens is the most important part of the equation. Especially if you want to use very high resolution camera. The most important feature to look for is image sharpness and its homogenity (some lens are very sharp in the center, but blurred in the corners).

A rule of thumb I used for many years: put 50% of your budget in the camera body and 50% in the lens.
Nowadays, in the digital area, I would even spend more on the lens, because these don't depreciate as fast as the bodies.

Never buy a lens without a try. Don't base your choice on somebody's experience or on a published test. Lens quality is very inconstant, and one sample of one model may be very good while a second sample will be very poor.
I always try before buying by taking a few photos of a newspaper page fixed on a wall and some photos of a brick wall (or any regulary textured object). Zoom 200 % and compare the sharpness of the center and the sharpness in each corner. If you find important differences, don't buy it.

125

General / Optimization generates heavy noise in sparse cloud

« on: August 17, 2014, 07:14:44 PM »

I have 12 vertical aerial photos of a castle (acquired with a 28mm lense from about 800m flying heigth) and 150 oblique views acquired with a 135mm from different angles (2 x 360°) at flying heigth varying between 300 and 150m. All photos are well exposed and sharp. They are all referenced (GPS data stored in Exif)

I import all photos in the same chunk. They all align fine (using "ground control" or "disabled" option).
I have a few (4) ground control points, not very accurate (obtained from Google Earth). Alignment error is about 5m. I add 20 markers using guided approach, and on most photos, proposed placement is fairly good, and when needed, I have adjusted the placement manually.
The resulting sparse cloud is not too bad (noisy, but geometrically coherent).

If I optimize this sparse cloud, either using fixed camera calibration or not, the "optimized" cloud becomes very noisy, with many pikes and wrongly oriented sub-parts. As you may expect, derived dense cloud is not good...

Any suggestion will be welcome.

126

General / how to relate cameras and wrong parts of a cloud ?

« on: August 15, 2014, 02:41:23 PM »

I'm trying to produce models of urban sites using both vertical and oblique photos acquired from an helicopter.
Sometimes, I got relatively good results, but some parts of the low-density cloud are obviously wrong:
a sub-cloud stretches outside of the model, rougly oriented on a oblique plane.
This suggests a wrongly computed camera orientation.
I have enough camera to remove a few badly oriented, but finding the culprit(s) is another story !
The only solution I found so far is to remove camera one by one and see the result in the model window.
As I often work with a few hunderds cameras, this procedure can be very tedious, especially if there are a few wrongly oriented parts of the cloud.

Is there a solution to:
a) select one camera (or group of cameras) and highlight corresponding parts of the cloud
or
b) select a part of the cloud and identify which camera(s) are involved in its construction.

(Otion b will of course be easier for my specific problem)

127

General / Re: Is it possible to form a tree model with Agisoft?

« on: August 15, 2014, 01:54:54 PM »

A serious problem with photogrammetry (in general) of trees seems related to the fact that leaves and even branches are moving because of wind, and this generates "false parallaxes" that are interpreted as depth difference.
Same occurs with moving objects like cars and pedestrians on aerial photos.
If the movement is important, these objects will be probably neglected, but small displacement of leaves will generally generate wrong positions and hence produce a fuzzy 3D model.

The only solution I have for this is to avoid acquiring photos in windy conditions...

128

Feature Requests / Re: align bounding box to GCP coordinates x,y,z planes

« on: August 15, 2014, 01:45:08 PM »

Thanks a lot.
This is exactly what I was looking for !

129

Feature Requests / Re: align bounding box to GCP coordinates x,y,z planes

« on: August 13, 2014, 01:08:42 AM »

Could you please be more precise: where can I find this sample script in the Python scripting sub-forum ?
I found the symmetrical one (modify the axis to match the bounding box, but not the box2axis one.)

Perhaps you could paste the script here ?

Thanks

130

General / Re: Areal Photogrammetry with Sony Nex7

« on: July 14, 2014, 10:28:01 PM »

does it accepts a remote controller ?

will you use it from an UAV or a "normal" plane ?