Messages

256

General / Re: Combining terrestrial (ground based) photos with aerial (uav) images

« on: May 16, 2017, 10:52:14 AM »

Hi everyone !
I'm actually doing my master thesis in photogrammetric methods for topographic surveys.

Some tips I could give you:
- Integrated GNSS data are not mandatory: Indeed they are never better than a couple of meter accurate. So you will need well-known GCPs to accuratly georeference your model. I usually untick pictures georeferencement when handling survey with our Phantom 4 Pro (Really nice camera by the way).
- Ground pictures will permit you to fill your holes under trees: I'm actually using GoPro camera at the top of a pole. Even everybody are scared about fisheye lens for photogrammetry, I can tell you it's possible ! I was actually able to handle super high accurate measurement using GoPro (I mean sub-millimetric accuracy)
- The secret is overlapping: The more your pictures overlap each other, the strongest will be your model. And don't be scared about number of pictures. I've actually noticed that a stronger bloc with a huge amount of pictures can be calculated faster than a smaller number of pictures weakly linked. (Here is where GoPro camera makes it stronger because of the laaarge field of view)
- Coded targets give you the possibility to save a lot of time in processing: and will give you more confidence on reconstruction. I postpone you to my topic talking about coded target size before print them.

Hope it helps !
Regards

257

General / Re: merged chunks accuracy

« on: May 16, 2017, 10:23:01 AM »

Hi Ugo !

I have posted a lot about that.

Before merge chunk, there is align chunk. How did you do handle that ?
What is the accuracy you talking about ?

I have noticed that point based alignement is pretty weak as it doesn't give you any alignement RMS error. So you have no idea how it went...Did it work or not...nothing...
But on another hand, I would say if you are able to align them based on markers, you may have a georeferencement or a scaled system ? If it's the case, you won't need to align them before merging.
Regards

258

General / Re: 1.3.2 Change Log

« on: May 16, 2017, 10:16:41 AM »

Thanks Bob !
Actually Diego quickly gave me that at the beginning of this post !
I just answered to highlight it could be the case for others not to be able to get the latest Change log

Regards

259

Feature Requests / Re: Add info about volume error

« on: May 16, 2017, 10:13:53 AM »

Hi Lexa !
According to Pix4D calculation method for volume error, you should be able to really easily calculate your own volume error using:
Volume error = Area surface x GSD x 1.5

Indeed it could be nice if something might be directly add in "Measure Shape" panel.

By the way, it could be also interesting to add other base plane. Indeed, we are able to do what we want with "flat" base plane using "Mean level" and "Custom level". But when it goes to not flat area, there is only "Best fit plane" available.
I could firstly imagine something like "Custom level best fit plane", where it could be possible to verticaly translate the best fit plane, for example to make it passing by the lowest point.

Regards

260

General / Re: 1.3.2 Change Log

« on: May 16, 2017, 09:52:15 AM »

Hum... i'm gonna start being mystified... 
I've updated tens times the Download agisoft webpage since yesterday, but I'm still only able to get the 1.3.1 change log... 
Never mind, I got what I needed.

Thanks again Alexey to have quickly answered to my suggestion of image centering

261

Bug Reports / Re: Center image on selected marker

« on: May 16, 2017, 09:21:54 AM »

Yes it does !
Warm thank you for that !

262

General / Re: 1.3.2 Change Log

« on: May 15, 2017, 07:06:07 PM »

Thank you !
Still impossible for me to get the Log by the way ^^

263

General / 1.3.2 Change Log

« on: May 15, 2017, 06:26:49 PM »

Hi PhotoScan support !

Would it be possible to publish the Change Log of the 1.3.2 release ? Or to give some infos about novelties ?

Regards

264

Camera Calibration / Re: Calibration questions on Dji Phantom 4

« on: May 09, 2017, 10:43:06 AM »

Hi barrubba !

Yes basically we could calculate a accurate calibration using Agisoft Lens...

But there is still the problem of the chess board... The calibration has to be made with the exactly same parameters as the survey will ! So as I explained before, at 15m or more, far from a huge chessboard.

And even though a solution can be found... I've noticed that the P4Pro doesn't "save" the camera parameters when turned off. So each time we start the UAV, the camera is set up as default (focal distance for example). So I easily imagined we cannot get the exactly same focus between two flights...
So... would it be impossible to handle very accurate measurements with that kind of device ?

265

Bug Reports / Re: Marker Problems since the latest Update

« on: April 28, 2017, 09:23:26 AM »

Hello Alexey !

Thank you for this explanation.
Is there the possibility of deactivating those automatic projections ?
Indeed, when working with huge amount of pictures, it would be easier to manually place markers or shape vertices on a few pictures (ideally placed) than delete or refine automatic projections on a huge number of pictures...
And I guess a wrong automatic projection that we forget to delete/refine would completely break the block aronde this place ?

It's especially the case when handling ground photogrammetry with fisheye lens and a 45° pitch. The horizon is almost always visible as well as the upright of the place. PhotoScan then supposed that almost every pictures are overlapping each others (that makes workflow f*cking longer) but also place automatic projections everywhere...and create a big mess !

Hope something is possible !

266

Bug Reports / Re: Marker Problems since the latest Update

« on: April 27, 2017, 11:25:03 AM »

Hi Alexey !

I take the opportunity to ask you what is the aim of blue flags ? What is their role ?
As they are kind of intermediate role between grey and green ones.

- Grey flag: Presumed position of a marker in a picture. Only indication, no role in calculation.
- Blue flag: ? ? ?
- Green flag: Defined position of a marker in a picture. Used in calculations.

Thanks in advance

P.S. To my mind for the moment blue flags only scare us and we have lots of difficulties to deal with, and that the same with "refine marker projections based on image content" preference setup. Sometimes moving, sometimes not...

267

General / Re: Recommended Gradual Filter Settings

« on: April 27, 2017, 10:45:20 AM »

Hi engelbeck,

I've read your references with lots of interest.
However, I didn't find many deep explanations about Reconstruction uncertainty and Projection accuracy filters. I would say it's only some feed back for experiences

So I would also like to have a bit of help by Alexey of those points

About image count: I'm aware about overlap factor in accurate reconsctruction. Indeed, I always use a minimum of 80% band-overlap and a minimum of 60% side-overlap. So I get quantity of tie points matched on more than 2-3 photos. Nevertheless, I never delete 2-photos-matched-tie-points using the filter, because it would reduce my tie point could size by two (or even more for more basic reconstructions), and this amout of points are really precious in order to calculate precise and global camera calibration, which is really important.

268

General / Re: Chunk Info - Meaning and Units

« on: April 25, 2017, 07:48:36 PM »

Hello Alexey !

Ok fine !
So may are we able to get the real effective overlap, based on used tie points ?
We can easily get an overview of the tie point overlap using image count filter but a global value would be nice to characterize the final adjustement before going further in the workflow.

Regards

269

General / Re: I DONT SEE OPEN CL TAB IN PREFERENCES,INSTEAD SEE GPU

« on: April 25, 2017, 10:09:36 AM »

Hi Alexey,

I've read the whole topic with interest but I would need some more argmuentations about:

- if the coordinates for the markers are valid, optimize camera alignment (all parameters excluding K4, P3 and P4, but including rolling shutter optimization)

Firstly: Why do you suggest excluding K4, P3 and P4 ? Those parameters have very few influence on distortion as they are very last coefiscients. But I can imagine you don't say that randomly.

Secondly: I may ask you more about the rolling shutter optimization. I never went deeply on this subject but I've noticed big movement when optimized it. I'm taking the liberty of asking your famous short but efficient explanation on this subjet (Even I know it may be not the right place to do it)

Regards

270

General / Re: Chunk Info - Meaning and Units

« on: April 24, 2017, 06:49:36 PM »

Hi Alexey !

Thanks again for your priceless help !
I've found nearly all I was asking about in the "Chunk info" dialog.

Nevertheless, it remains a little problem, about the effective overlap value.
Indeed, if this value is based on used tie point, it would change after filtering. And even more after deleting point selected with "image count" filter (Then the effective overlap would get higher).
But, after some experimentations (several filters applied, adjustement...), I was not able to make this value change.
Is there something i misunderstood ?

Regards