Aerial Photogrammetry Phantom 2

[Darko]

I have too. Done some testing and the results are not that fine as I have with the Hexa and Samsung NX1000. My testing area was 300x200 m and there I had 5 lines with the 50 m distance. Intervalometer was set to 3 sec and the flight was 100 m above the ground. The New beta PhotoScan 1.1. did the job perfectly OK.
I had 18 controll points measured with the RTK GNSS. Six of them were used as a GCP and 12 just for the precision estimation. Those 6 points were set in the top and bottom raw and the result is :
Position +/- 15cm. That is more than I've expected. The ground resolution was about 3cm

With the Samsung I've flown the same area. The lens was 20mm (30mm equi.) exposition set to 1000, aperture 8, flight eevation 125m and the result is much better pictures with :
Precision +/- 5cm. The ground reslution was 2.5cm

So, the final decision is that Phantom is acceptable for some jobs with lower precision but considering it's price and simplicity it is wonderfull.

[MortarArt]

Darko, the Phantom 2 can carry your camera. You don't need a Hexa for that, unless you're also using a gimbal, which is useless for photoscanning.

I sell camera mounts for that exact purpose.

[gheflorian]

Gheflorian; I think I answered your question about GPS logs in the other thread. They actually do log them, if you follow some simple instructions on how to communicate with the onboard computers.

As for a 'flight plan'; the Phantom 2 Vision & Vision+ (which are identical so far as 3D scanning is concerned) both have inbuilt ground station support, with up to 16 waypoints via the Android & iOS control apps. This is not the same as the regular, full, DJI plug-in ground station, which is run from a laptop, but fully compatible with the whole Phantom series.

If your budget is not much of a concern though, I'd suggest ignoring the Visions, as their cameras produce inadequate results. Get the Phantom 2, get a good, light, compact camera such as a Sony RX-100 or Samsung NX-1100, put a mount such as this one on it, get the BTU ground station unit and a Flytrex Core for GPS logging.

Thank you very much and sorry for the late reply. Actually budget is a concern in Romania. Can someone please provide a link with Raw images from a project? I would pretty much like to do some tests with Photoscan.

[Kiesel]

Hello Mortarart,

for me your link to your camera mounts is unfortunately not working.

Karsten

[mrb]

Darko, the Phantom 2 can carry your camera. You don't need a Hexa for that, unless you're also using a gimbal, which is useless for photoscanning.

I sell camera mounts for that exact purpose.

Actually, a gimbal is very useful for photoscanning, if you hope to have any control over the orientation of the camera.

[Darko]

It is not only the gimbal.. I have 50 WP on my DJI Wookong Ground Station and 1W data modem that works on 10km distance (not tested). My flight speed is 12m/sec and with the 16A/4S battery I can stay in the air for 30min. My Ground station is Sunbook netbook with 100% readable screen on the direct sunlight. Lots of advantages and also the automatic waypoint grid creation in the Ground station software. That is serious hardware for serious jobs.

[JimBarmore]

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.

[MortarArt]

The link is working again. I reorganised the categories on my page as I've released a number of new options for camera mounts.

Here it is again

And the following images should function as links to each of the current models:

Hinged mount V2



1D Gimbal Beta



Heavy mount

Actually, a gimbal is very useful for photoscanning, if you hope to have any control over the orientation of the camera.

A hinge is all you really need, if you're willing to take the time to land and re-shoot particular details that are not on the right angle, ie one flight for ground and roof, and another for walls. I have now released a 1D gimbal, although it is currently only in beta. It will definitely hold a camera, and do vertical and horizontal shots, and the servo motor from the P2V does tilt the camera, but I have not got the 7th channel on the controller working yet, so it's effectively proven as just a stabiliser.

It is not only the gimbal.. I have 50 WP on my DJI Wookong Ground Station and 1W data modem that works on 10km distance (not tested). My flight speed is 12m/sec and with the 16A/4S battery I can stay in the air for 30min. My Ground station is Sunbook netbook with 100% readable screen on the direct sunlight. Lots of advantages and also the automatic waypoint grid creation in the Ground station software. That is serious hardware for serious jobs.

That's great range! What camera are you flying? BTW DJI is in the process of releasing an SDK, and Pix4D is releasing an purpose built ground station for Naza for photogrammetry based on it. DJI flight systems were already accessible, since they're just an implementation of Linux, and you could feed custom commands into the drone via the systems used in the Vision ground station app, but that was only accessible to people using those crappy little cameras. I'm hoping to get it working with my NX-1100 some point after the release.

I'll also be testing the servo with heavier cameras, and attempting later on to implement a form of surface scanning, via a single board PC & Asus xTion, so that I can tilt the camera onto the correct angle for shooting in an automated fashion. It's a difficult project, but definitely possible.

[Kiesel]

working link  : http://www.shapeways.com/shops/mortar_art

[stihl]

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.

[stchris]

Hello!

I'd like to use photogrammetry (PhotoScan) and the phantom vision 2+ to process a stripe of a mountain/hill to a 3D-Model.
The stripe will have a length of 300 meters, a width of 50 meters and a height of 120 meters (so quite steep).

What would be the best approach to capture such an area?
If I'd capture from top-down, would I need to capture all images from the same height?
For example: fly at 150 meters in a grid-pattern

Or would it be better to always fly at e.g. 30 meters above the ground from left to right and step-wise go higher along the hill?
Or even another approach?

Thank you for your advice!
Chris

[stihl]

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:

[Marko Kohv]

Im geologist from Estonia and have used DJI phantom vision + for Photoscan models. Mainly for larger features like quarries, mounds, high outcrops. Simply the places that are too difficult or impossible to reach with hand-held and far-better camera.

You can see some of them here : https://sketchfab.com/markokohv/models

I usually fly at 50-90 m above ground, first round straight down "lawn mower" pattern; second one with 30-40 degree angle, "star" patterns. The concrete flight plan should of course depend from the object and your particular points-of-interest.  Phantom has ground-station mode but has by-default restrictions for max distance. I use unofficial app (check www.phantompilots.com) that has this restriction removed and lots of other useful tweaks.

I use built-in interval mode (3-4 sec), highest quality jpeg. It is possible to use RAW format (that gives far greater freedom in post-processing) but it takes up to 20-30 seconds for writing to SD card and that is too slow for aerial mapping. However its great option for "coverphotos".

 I mainly use rtk GPS for ground Control Points (usually 10-20 of them), if you dont have rtkGPS available than you can use scalebar approach to at least get correctly scaled model in local coordinate system.

I usually post-process the images with Lightroom (contrast , exposure, noise reduction etc). I did some comparisons and this step improves the quality of the model significantly.

Phantom adds GPS coordinates to EXIF and this help photo alignment a lot. It does not log the altitude, so its best not to change this too much.

The ortophotos that I have produced have pixel size close to 3 centimeters, the model accuracy is usually within 20 cm, comparable to usual airborne lidar and enough for my applications.

Its really great machine if you keep in mind its complete, ready-to-fly, 1200 euro UAV. You can get better results but either it costs way more money or personal tinkering time.

 

[MortarArt]

Marco Kohv; which model did you buy for 1,200eu?

The Phantom 2, with an NX-1100 & my mount should cost less than $1,000usd.

Also; how do you get the Exif data?

[mrb]

He's talking about the Vision 2+
The Vision camera logs the exif and you can pull it.

MortarArt, inspired in part by your posts I'm 3d printing iterations of a 90-degree down-facing mount for an nx100 iii that can be swapped out for a h3-3d gimbal and gopro.  I think that will prove to be the most versatile setup - gopro for 4k video and photos, and the nx-100 for orthophotos.

Marco Kohv; which model did you buy for 1,200eu?

The Phantom 2, with an NX-1100 & my mount should cost less than $1,000usd.

Also; how do you get the Exif data?