Messages

61

General / Re: Simple workflow question - build geometry?

« on: April 11, 2013, 02:55:42 PM »

RalfH,

Thank you for the response.  I believe you have answered my question.  I will continue to do various testing but for now, if I am running independent checks on the results and they are falling within my tolerances then I guess I should be satisfied with the results.

Cheers!

62

General / Re: Simple workflow question - build geometry?

« on: April 11, 2013, 05:06:04 AM »

Hi guys,

I wont be commenting on your conversation as it is well beyond my level of expertise but I do have more information based around my original question...

For a particular data set I am testing with at the moment when I export the sparse point cloud in xyz, straight after aligning photos, the output file size is around 200mb and contains about 4.5 million points, large but within reason.  After running build geometry and exporting the dense point cloud (also xyz) the file size was around 40gb, no idea how many points this must contain!  40gb is no use to anybody as I don't know of any programs that would handle a file of that size.  I built the geometry with a limit of 2 million faces as I thought this would produce a smaller (more realistic) output file size.  Hopefully you can understand where I am coming from.  If build geometry doesn't improve the accuracy of the individual sparse point cloud points then I don't see the need to complete the build geometry stage??  As the sparse point cloud, one post-processed through other software packages, seems to be delivering satisfactory results.

I am using a UAV (MAVinci) to perform aerial mapping over areas up to 70ha with a GSD of ~2.3cm, approximately 1000+ images, 75% overlap and 10 GCP's with accuracy's known to around the 30mm mark (RTK GPS).  I am requiring the finished product to be good for around the +-150mm and that is what I seem to be getting with the sparse point cloud.  I am mapping mining areas in Australia so don't need every bump and lump to be modeled, I just need a reasonably accurate model of a large area for volume calculation purposes etc.

Am I missing something here completely or is what I have determined correct?

Thanks!!

63

General / Re: Simple workflow question - build geometry?

« on: April 08, 2013, 03:39:45 PM »

Thanks for that.  I suppose I could just perform some tests of my own to be certain.  But I guess if I can check my results against independent data and the results are satisfactory then what more do I need?

 

64

General / Re: Simple workflow question - build geometry?

« on: April 08, 2013, 02:40:00 PM »

Thanks for the reply.

The sparse points clouds I am getting are in the millions of points and I don't really need any more than this, as I normally decimate that figure down to the hundreds of thousands anyway.  Otherwise the output file sizes are too large for most of my clients to handle.

Does "build geometry" improve the accuracy of the original point cloud points or does it just add more points/facets?  Bearing in mind that I am processing up to 1 square km per project and don't need every stone and bump modeled.  The point spacing of my final outputs, once I've post processed it, is around 1/2m so is it worth me doing this extra step?

Thanks.

65

General / Simple workflow question - build geometry?

« on: April 08, 2013, 02:00:48 PM »

Hello all,

This is probably a simple question to many of you, but I am new(ish) to Photoscan and just need some clarification...

I process aerial photography from over mine sites, quarries etc and after the align photos stage (plus adding GCP's and optimization) I have my 3D point cloud.  I can export this point cloud (sparse) and then tidy it up in other software packages and the results seem to be very good.  I am only really needing a 3D model and orthophoto and both of these I can export after the align photo stage.

Q. What extra benefit do I get from the build geometry step?  Does this step tighten up the accuracy's or is it actually for another purpose?  I am having trouble getting my head around this part of the software.  Due to it being a time consuming process, if I don't really need it I'd rather not do it!

Your replies will be appreciated.

Thanks.
Matt

66

Bug Reports / Re: Crash with 51 seconds remaining in build geometry step

« on: April 08, 2013, 12:34:42 PM »

Hi Alexey,

I didn't get a chance to do that, the program just closed.  Unfortunately I cannot give you any more details really.

Cheers,
Matt.

67

Bug Reports / Crash with 51 seconds remaining in build geometry step

« on: April 08, 2013, 11:46:18 AM »

Hello all,

Photoscan just crashed on me with only 51 seconds remaining in the build geometry step!  There was no reason given for this, it just said "Photoscan has stopped working and the program must close".  I have built geometry on this same project with the same settngs previously and it worked fine.

Any ideas as to what may have happened?  I am running Version 0.9.0 Build 1586 64bit.  Is it possibly a windows issue?  If this happens while working on a clients job it may become a bit of an issue!

Cheers,
Matt.

68

General / Re: After alignment some photos do not have error values?

« on: January 21, 2013, 02:36:24 PM »

Thanks Alexey

69

General / After alignment some photos do not have error values?

« on: January 20, 2013, 06:03:09 AM »

I noticed that after photo alignment a few of the photos did not have error values associated with them (only 9 out of 735).  They seemed to be restricted to photos around the outer boundary of the job.  What is the cause of this and can it be corrected?  Should I be disabling these photos before building geometry?

Thanks.

70

General / Re: How many points per image should I detect?

« on: January 20, 2013, 05:54:08 AM »

Hi guys, thanks for the replies.  That was what I suspected.  I might just do some testing myself and see what sort of differences it makes having less points.  I guess the best way to know something for sure is to test it yourself!  Maybe if the photoscan team read this post they will be able to give me more 'inside information' as to where the 40,000 came from.

Cheers.

71

General / How many points per image should I detect?

« on: January 19, 2013, 12:58:09 PM »

Hi all,

Can anyone help me with determining how many points per image that I should detect?  I see the default is 40,000.  I fly low level UAV aerial photogrammetry with a 20mm lens and images around 8.5Mp each.  I can only assume that less points will mean faster processing but less accurate orthos and DEM.  Is 40,000 the recommended or should it be higher or can I get away with less?  Obviously the faster I can process my data the better but I do not want to compromise too much on output quality.

Thanks!

72

General / Re: Can I reduce the orthophoto resolution/quality during export?

« on: January 14, 2013, 12:29:49 PM »

Thanks Porly, I'll give that a go.

73

General / Can I reduce the orthophoto resolution/quality during export?

« on: January 13, 2013, 10:45:24 AM »

Hi,

I am processing up to and sometimes over 1000x8.5Mb images from the Mavinci UAV but when I export the orthophoto I have to do it in blocks due to the size of the datasets.  Is it possible to reduce the resolution of the orthophoto so it can be exported as a single image file?

Thanks!

74

Feature Requests / View snap buttons

« on: January 13, 2013, 04:16:01 AM »

Hello all,

I think a good feature to add would be some 'view snaps'.  Just a few buttons on the toolbar that instantly take you to top view, side view (left and right), bottom view etc.

Cheers!