Messages

31

General / Re: which camera for low-altitude aerial photography (for use with PhotoScan)?

« on: April 08, 2013, 11:03:23 PM »

The Sony Nex 5, 5N or 7 are all great choices. They are low in size and weight, which can be controlled with an infrared controller by your RC. They also have interchangeable lens which will give you an advantage for what you're looking. Either way you should always take into account the size and weight of the camera and that will depend on which UAV you have. If you have a multirotor they can handle many cameras, but the heavier, the less flight time you'll get.

In my opinion the sony Nex 7 is one of the best cameras out there for low altitude aerial photography, but if you aren't looking for something that good the sony nex 5n will do and it is between 600-700 US$.

Regards,

Santiago

32

General / Re: Transmission line profile mapping

« on: April 01, 2013, 07:44:55 AM »

Thanks guys,

Lui I agree with you, the best option here would be LIDAR, but I have to say what Phisan posted is truly interesting. Although when looking at the accuracy XEOS can achieve even when using ground control points (20 cm vertical and horizontal), can't compare to LIDAR.

I'll look more into SimActive's Correlator 3D, it seems interesting, but I get a feeling it's not design for every UAV with a common camera out there. Unlike Agisoft or Pix4d it does ask for orientation parameteres like angular values, which I can't obtain from my UAV's.

Regards,

Santiago

33

General / Transmission line profile mapping

« on: March 18, 2013, 08:45:09 PM »

HI,

A company asked me to do the following job for them, but I really don't know if it could be possible with photogrammetry. We have a Hexacopter and a Lehmann Lp960 for aerial mapping equipped with a sony nex 5n 16 mp. The job consists in:

Create a profile on some transmission lines (power lines) that extend 150 km. They need to know were the lines are with respect to the terrain (including vegetation so no need to remove it). What I don't know is if the photogrammetry techniques can accurately model this transmission lines. Here's an example of what they need.

http://www.powerlinesystems.com/pti/ptipaper.html

I think that this job could only be done accurately with terrain techniques or LIDAR, or if anyone here has had any experience with a similar job It would be great to know your experience.

Thanks

Regards,

Santiago

34

General / Re: Trees!

« on: March 10, 2013, 12:34:46 AM »

Hi Herman,

Thanks for your reply. I know what I was doing wrong now, I was exporting the .las file in WGS84 and it had to be exported in a projected system (meters not degrees). Still after processing the data I wasn't getting any good results so I tried talking with Martin Isenburg, the creator of lastools. He asked me to send him the file I was creating and afterwards he answered this on a thread. If you guys are interested you can look at it here: https://groups.google.com/forum/?fromgroups=#!topic/lastools/oK81EEr7W3Y

Also it seems global mapper can handle some of that data much better than ArcGIS, I'll give it a shot.

Regards,

Santiago

35

General / Re: Trees!

« on: February 18, 2013, 11:21:26 PM »

Hi

I have experimented with the LASTools and the results looks very promising.  Trees, and buildings where very successfully removed. It is semi desert terrain and a mining operation , but still very
impressed with the ease and the speed.
I only struggle with a huge shift in the LAS data, this seems to originate in PS , not in LASTools.
Would appreciate any possible explanation for this

Regards
Herman

Hi Herman,

Could you please explain how did you manage to do it. I tried it by exporting the points in a .las format from Agisoft, afterwards I used ArcGIS using the lastoolbox that came with the las tools file. I used lasground to create another .las file that had vegetation correction but when the process was over it didn't create anything. Do you know what I'm doing wrong? Did you use ArcGIS to do the processing? Do you have the free version or the licensed one?

This is a very interesting tool, I would be using it very often and off course would be willing to pay for it, but not before I know it does work.

Best Regards and thanks for any feedback you can give me,

Santiago

36

General / Re: Once again about DEM and 3D accuracy

« on: November 20, 2012, 05:28:02 AM »

Hi,

I'm new to Agisoft and tried the trial version of photoscan pro a few days ago. The report said my error was 0.497 pix and my ground resolution was 0.077 m/pix. I asked the support team to explain the results to me but their explanation didn't clarify my doubts. They told me an error <0.5 was considered to be good, but I want to know what's the error in meters for my project. Or compared to a total station or a RTK GNSS how did I do. Do you know based on what do they say <0.5 is good.

Thanks for any help you can give me.

Best regards,

Santiago