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Messages - stihl

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361
General / Re: Distorted Ortho
« on: December 27, 2014, 07:41:31 AM »
Improper geometry of the roofline and the staircase is due to noise and/or inadequate height data (point data) of those locations in your dense point cloud.

Increasing the overlap and/or lowering the GSD of the images (ie flying at a lower altitude) will increase the amount of points that can be generated during alignment process and dense cloud generation. Thus creating a more complete pointcloud which will improve the geometry. Unless extensive use of oblique imagery is used, camera position data isn't that important. I assume you used nadir only images.

362
General / Re: meaning of vertical resolution and vertical accurancy
« on: December 24, 2014, 09:08:40 PM »
With vertical resolution I think he meant the GSD ie Ground sampling distance. A GSD of .1m is a GSD of 10cm which translates to one pixel in the photo equals to 10 centimeter in real life.

A horizontal accuracy of 5 m means that anything on the XY plane is accurate within 5 meters of reality and this is the same for the vertical accuracy of 3m which only accounts for the Z-axis.

363
General / Re: dense point clouds and depth filtering
« on: December 20, 2014, 05:23:39 AM »
Interesting results.

May I ask at what limit did you set the tie-points at for aligning?
Also what are the images resolution and how many tie points were found in each image on average?

364
General / Re: Big Data Project
« on: December 18, 2014, 11:50:26 PM »
Shouldn't be an issue if you do some effective pre-processing and make sure to slice the project into chunks for processing. With one computer with hardware worth about 4 thousand dollars I've processed a single aerial project that consisted of over 80.000 images. If you chop it up and manage it well all it takes is some time.

I wouldn't unite or merge chunks in Photoscan. Instead export them individually and merge into a sophisticated GIS program like GlobalMapper.

365
General / Re: scale does not export
« on: December 16, 2014, 12:33:55 AM »
I think you need to optimize it first for it to keep that scale. Did you do that?

366
General / Re: Problem with align of forested images
« on: December 10, 2014, 09:27:05 PM »
Are those the original images? As in are the made photographs 800x600?

367
General / Re: Aerial Photogrammetry Phantom 2
« on: December 09, 2014, 04:28:42 PM »
It's important to fly at the same height over the terrain. This allows you to keep the same GSD throughout the project so some portions of the model do not look less detailed than others.

The best is to fly in a lawnmower pattern like this:


368
General / Re: Aligning points - point limit
« on: December 08, 2014, 05:46:16 PM »
I'm not sure why the default is set to 40 thousand points. I've seen other photogrammetry software that used anywhere between 20k and much much more.

I've tried aligning aerial projects with the maximum number of tie points (setting the value to 0 will do this) and it will find roughly between 200k and 300k tie points per photo. This means that the aliginment takes longer, but I've also noticed that the dense point stage takes far less time. I assume because it has less space to fill in. I've also noticed that the geometry is more complete if the pictures are clear and sharp if I use the maximum tie points allowed.

369
General / Re: TLS file format
« on: December 05, 2014, 09:50:02 PM »
Hi Darko.

I wasn't aware of any TLS file format. Nor did I find any information about it on the web nor could I find any export options regarding 'TLS' in Photoscan...

Did you mean Tiles instead?

370
General / Re: DEM
« on: December 03, 2014, 05:11:51 PM »
What you need is GIS software.

Try GlobalMapper, it's free to try as far as I know. It can calculate volumes in a DEM depending on a set height, average ground height or actual ground height.

It should also solve your coordinate issue with the TIFF.

371
General / Re: Change in coordinate system
« on: December 02, 2014, 12:15:13 PM »
What you need to do is convert the WGS84 GPS coordinates from your onboard GPS in your device to the UTM that your ground control points use.

What CRS are your GCP's in?

372
General / Re: GPU processing failed
« on: December 01, 2014, 02:54:39 PM »
Oh that's unfortunate....

In that case I'm out of options. The only ones I can find for your card are v.344.xx which I assume produces these failures. :-\

373
General / Re: GPU processing failed
« on: December 01, 2014, 11:57:39 AM »
Hi

Yea that's due to a driver issue. Because the GPU fails during the dense cloud process it reverts back to the CPU which is immensely slower for this step than the GPU.

The solution is to roll back to driver version 337.88.

374
General / Re: Aerial Photogrammetry Phantom 2
« on: November 18, 2014, 06:31:52 PM »
Hello all,

Just some quick questions regarding ortho photo workflows. I'm a beginning photoscan pro user and have had some success at producing orthos with the phantom 2 vision + (that's why I'm posting here BTW). I'll have access to RTK GPS in a few weeks so I can produce GCPs. However, at present I am wondering if the following is possible without GPS:

1. Can markers be placed to help the alignment of photos so as to fix some minor issues like straightening out rooflines and vehicles (sometimes cars look like shit)? Can these markers be placed and utilized for this purpose without GPS coordinates?

2. Can the scale bars be used in a similar fashion, by placing markers without GPS coordinates, and with photos taken from the phantom 2 vision +?

3. And finally, does the phantom's onboard camera record GPS altitude? I ask because in looking at the EXIF files I only see lat and long (been wanting to know this for some time).

Any help would be greatly appreciated - just steer me in the right track. I'm very interested in learning more about better flightpath software and techniques for mapping with this phantom 2 vision +. Thank you.
Hi Jim,

To answer your questions;

1) Markers can be placed to help  the alignment of the Ortho image. Preferably what you want is both GPS flight positions from the UAV and GCP's measured with RTK GPS. It can be done without flight positions but then you need an extensive GCP network as well to prevent the model from bending.
GCP's will not noticably help with artifacts that you see on building edges and other height objects. The only solution for that is extensive noise filtering (artifacts show up because of irregular height data near edges) but this is time consuming and annoying. I prefer other software to create aesthetically pleasing Orthomosaics.
They can't be added without GPS information. What you mean are manual tie points which Photoscan is unable to do so as far as I know.

2)Scalebars can only scale the model. It can't position it relative to the real world nor can it say anything about it's absolute orientation.

3) If you don't see height in the EXIF data it's safe to assume that it doesn't log it. Only way to go around is to manually add the height if you know the flying height during that time. Of course the height varies during the flight so you can't use the model that's generated this way for it's heights unless you add accurate GCP's and have it optimized just on the GCP's.

375
I believe under Tool > Camera calibration you can enter the fixed focal length in the top right of the camera calibration window.

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