MicroSD cards and standards …

There is a lot of confusion about the speed of MicroSD cards these days and various standards exist. Overall its easy to buy yourself into the wrong card type and for copter data acquisitions with the P4Pro the card speed is essential.

So here we go:

UHS-I and UHS-II (Ultra High Speed Classes):

UHS-II is the newest standard but is not supported by many yet. The Phantom series 3 and 4 all need UHS-I and definitely the fastest UHS-I cards. The UHS-I bus goes to 104MB/s whereas the UHS-II bus goes up to 300MB/s  (theoretical limits – the cards will not perform at this speed).

u1-u3 Rating:

UHS Speed classes are subdivided in to u1 and u3, while u3 performs minimum at 30MB/s write speed (needed for copter flights).

Video Rating: 

A new speed rating is called “video rating”. It scales from V6 to V90. The fastest cards are v60 right now (possible values are V6 V10 V30 V60 V90, but note that V60 and higher is usually UHS-II bus type and not supported by Phantom 3 and 4 series).

C-Rating (c1-c10)

Speed Rating up to 10MB/s write – this is a slow class rating and c10 should be always possible for fast cards.

SDHC vers SDXC:

Up to 32GB capacity the cards have the label microSDHC whereas cards bigger (64-256GB) hold the label microSDXC.

For the Phantom3A (5MB/s max write speed) Phantom3Pro (60mb/s =7.5MB/s) and Phantom 4Pro (100mb/s=12.5 MB/s) series the fastest at writing to card seems to be right now the UHS-I SanDisk Extrem plus and Extreme pro cards (90MB/s sequential write). While this seems overkill the u3/V30 just certifies that you will never be below 30MB/s write speed under real world / all temperature conditions.

  • SanDisk Extreme PLUS  microSDXC UHS-I u3 V30
  • SanDisk Extreme PRO microSDXC UHS-I u3 V30

Nice summary from Wikipedia goes here:

https://it.wikipedia.org/wiki/MicroSD

microsd

 

 

Speeding up Agisoft Photoscan

For some of the copter data processing folks Agisoft Photoscan turns out to be the most important tool/software to calculate point clouds, orthoimages and nadir data mosaics from copter  photographs.

Problem: very long processing times with dense point cloud calculations with high or ultra-high settings (full resolution image matching with SfM (Structure from Motion) algorithms).

Some nice net finds show how multicore processing has its limits and why you should invest into GPU performance … and in high end 3D graphic cards.

Combining more than 20 CPU cores doesnt seem to speed up the process and combining more than 4 GPU systems also doesnt seem to help. There is only a minimal speed increase when you add more CPUs and or more GPUs when a 24 core system is already installed.

http://www.nvidia.com/download/driverResults.aspx/115283/en-us
http://www.agisoft.com/downloads/system-requirements/
https://www.pugetsystems.com/labs/articles/Agisoft-PhotoScan-GPU-Acceleration-710/

It boils down to a dedicated system with 2-4 Graphic cards with 3D acceleration (GTX-1080ti cards from Nvidea or if you can afford it a TESLA p100 based system), with approx 64-128 GB RAM and a dual i7 system setup.

mtk – Sören

Schlachtensee Panorama

The higher resolution version of the Schlachtensee Pano shot / panorama from early February. This was a magic week. Temperatures and light were just perfect and the ice was incredible untouched. This pano is from the P3A.

For those not familiar with the Berlin south west. The Schlachtensee region is known in Berlin as the area where the people who love dogs used to have some conflicts with those that go for a run and/or the other way around.  I think the conflict has been cooling down now somewhat fortunately! In summer its great to have a swim here early in the morning. Skating in winter only works every 5-10years – so these days in February were kind of unique. (Pano from 4 different shots: resampled to 4300×1300).

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Phantom 4 Pro Flare Tests

Did some more tests with the Phantom 4 Pro:

The into the sun shots just capture a lot of flare and the sun star is very much Samyang 14mm like. This is an issue and it reduces the image acuity for 3D point cloud modeling for object measurements as well as for the landscape panorama approach.

The against the light shots look very much like the Samyang/Rokinon  14mm lens character. The sunstar has light rays that increase in size from the center and these rays cover the full frame of the 1inch sensor when the illumination comes from one of the outer edges. It clearly degrades the full image when the lens is stopped down to f.e. f8 but gets better when the lens is driven wide open. There seem to be some diffraction effects at work that are clearly not so great. You can drive the camera to generate sharp sun stars, but as usual here the characteristics of this star make a difference to some of us.  The Samyang like star is not so well received. The linked flare issue however is much more a problem because it is hard to avoid when you have the sun in your frame and when the lens is stopped down to f8 or f11. For some scenarios a lens hood may be useful but its only functional for those shooting scenarios where the sun is not within your FoV.

To be honest I am bit puzzled … this is the first affordable 1-inch sensor platform with nice resolution and better DR, but – the flare issue is likely killing some of the potential ideas that you might develop with this machine. A pitty!

Some examples:

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Comparison shot done with the Phantom 3A, clearly shows that the lens/sensor combi wont give the same amount of flare here (again different light level and different sun illumination angle):

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Phantom 4 Pro Tests

Have done some tests with the new Phantom 4 Pro that I am using in 2017 for some research projects on photogrammetric point cloud mapping. This is a remarkable step forward in terms of image quality. The Phantom 4 Pro just creates much better image detail and acuity and resolution/sharpness is on a much higher level compared to the Phantom 3A. Its just giving back the DSLR like quality on tiny airborne systems. Also SNR (signal to noise) is much better and dynamic range ist enhanced. Only problem so far seems to be a slightly higher sensitivity to flare but I have to do some more analysis on this one. Its difficult to compare the flare issue because you cannot create exactly the same exposure / image concepts for different copters in the air. It will always be a wee bit different. So some ground based comparison needs to be done here.

This is a game changer for photographers that need an airborne system sometimes. As simple as that. It brings the image quality that we wanted back and you always can add HDR and Pano techniques to add from that. Great times to let your creativity fly!

Some shots from recent test flights with the P3A and the P4Pro:

Bildschirmfoto 2017-01-22 um 17.23.46

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Multi Copter Photography and Photogrammetry

Multicopter Photography and Photogrammetry

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Late this year I bought a Phantom 3A (Advanced). The prices went down and these platforms are so affordable now that it makes sense to test it out.

The main applications for my work are multifolded:

  1. Special shootings for paying clients,
  2. regatta event shots from above,
  3. very early morning misty landscape stills and
  4. large scale or near range photogrammetric mapping for research purposes with applications in forest biomass mapping and archaeology as well as biotop-typ delineation and fine scale analysis of vegetation structure and slope stability analysis.

Clearly 1-3 and 4 will very nicely cooperate. Its just wonderful to experience how photography and research can come together here, makes me wonder sometimes how I managed to get into that cool spot where I get payed to fly a remote controlled camera … :-)

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Being not new to copter flying, I found the Phantom 3 to be really easy to fly. Once you mastered the documentation and some basic theory about controlling a quadro-copter its really a simple excercise to control these devices. This is mainly due to the perfect GPS controlled position hold of the Phantom. It just stays where you put it (in opposite to gliders) and this makes it also kind of boring to fly a copter. The DJI GO app that is used on a mobile device to check the telemetry data and to control the lifeview provides a nice overview about position, viewing angle and overall status of your copter. You can also modify shooting parameters, change the camera viewing direction and check speed, height and remaining flight time, battery status and the number of satellites. Other apps support fully automatic mapping modes with variable overlap configurations (Data Mapper or Drone Deploy).
p3a-on-backpack

P3 installed on a LowePro backpack fully functional with installed props and ready to fly in a minute.

Some DJI Phantom 3 A Specs:

  1. Image Data capturing in 12MP Adobe DNG RAWs, gimbal stabilized! & damped. 2. HDR with 5 exposures each 0.7EV under/over-ex-> RAW DNG HDR computation. 3. Sony EXMOR 1/2.3“, 12.4MP, 94°lens (20mm focal length equiv. tilt.), ISO100-3200, 8-1/8000s, single shot, multiple shot, exposure series (3/5), DNG RAW format, video: FHD upto60p, 2.7k upto30p, 4. Memory: MicroSD up to 64GB cat10.
  2. Control: GPS/GLONASS controlled position hold, visual Realtime-Position-Tracking (VPS – Vision Positioning System) up to 3m flight alt. (P4pro: 10m). RTH (Return to Home Funktion), Battery Low RTH, Security-RTH, software controlled flight altitude (override possible): 120m, autostart/-landing, beginner modi, (OrbitModi/anti- collision (infrared/ultrasonic)/ActiveTracking/terrain follow: P4/pro/Mavic), P-GPS – GPS controled stabilising (+/-10cm position), P-OPTI (optical position control & stabilizing), P-ATTI modi (flight altitude only (barom.) – copter could start to drift).
  3. Flight parameters: weight: 1280g, climb: 5m/s, descend: 3m/s, Vmax: 16m/s (ATTI) – 60km/h, flight altitude max: 6000 m (airspace above 100 m needs a clearance (approval), RC max distance: 5km, flight time: 23 min (30min: P4pro), RadioControl: 2,4khz RC with iPad/iPhone (build in DJI Lightbridge System), realtime lifeview control per DJI GO App.

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