“DJI GS Pro” – Ground Station Testing

Some tests using the DJI GS Pro (Ground Station) software for automatic flight programming with the Phantom 4 Pro.

New flight campaign at the Kuckenburg spot (Sachsen-Anhalt) finished with two different flight altitudes using DJI GS Pro – mapping the open archaeological excavation site of medieval church now in September 2017. This worked flawless – the only problem: you kind of need a mobile connection with your iPad. Since DJI GS is an iPad-only software I used a hotspot from the iPhone to bring the iPad online. Its not perfect but it works. Overall I find DJI GS Pro to be more easy to program and to setup than Drone Deploy. The interface has more option to setup – so it is at first more complex but it integrates into the DJI Go App and so far my impression is that it is not giving these unexplained copter start problems that Drone Deploy sometimes showed. GS also seems to be less integrated into a subscription model and looks like a standalone software solution – though a DJI account is needed. I havnt tested capturing DNGs. Its not a direct option as far as I can see – this could be a limitation. You can easily modify exposure times and f-stop numbers even when flying to geht sharper shots. There is however so far no option to switch from JPEG to DNG. As this is usually only limited by bandwidth it could be an option that is available when you decrease the flight speed (leaving enough time between exposures) – so not tested yet.

As an in-App purchase you also can automatically do POI flights – this is very handy for these dense point clouds of single objects and its not so straight forward to do this in manually POI mode as part of the DJI GO software (though also possible).

DJI GS Pro however has some strange ways to handle waypoints when you use the hover method but once you understand where the problem is (the number of waypoints is restricted to 99) – it works nicely. DJI GS Pro also comes with different modi – “Virtual Fence” is very nice for training and restricting the flight space, “3D-Map Area” is for mapping of larger areas and “3D Map POI” is for these POI flights where you want to map 3D object structures and where you have enough space between objects to create some kind of circumnavigation.

The full manual goes here: https://dl.djicdn.com/downloads/groundstation_pro/20170831/GS_Pro_User_Manual_EN_V1.8.pdf

Some shots from the Kuckenburg flight campaign with 500 DNG shots and approx. 50Mio and 80Mio points in different dense point cloud calculations with Agisoft. As we don’t have a SAPOS subscription for “Sachsen-Anhalt” no DGPS points were measured. However some fixed points from the FSU Jena excavation team will be used.

 untitled-20170919-d4c5abaf23a147c434e47d2a0105ac83-0680

kuckenburg-model-tiefbelf

Speeding up Agisoft Photoscan

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

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), with approx 64-128 GB RAM and a dual i7 system setup.

mtk – Sören

 

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

 

 

Using DroneDeploy and the POI mode for automatic point cloud mapping

Using DroneDeploy and the POI mode of DJI.

Have been doing some leaf-off flights now in March on one of my favorite sites for complex tree crown point cloud mapping. To add to the leaf-on data from last autumn.

sp-stand-leaf-off-2

Fig.: Leaf-Off point cloud with combined height color coding and reflectance color coding.

This time I also checked the full automatic flight modi using the POI (Point Of Interest) mode from DJI and Drone Deploy with the P4Pro and the P3A.

Both work perfectly although I believe the POI mode can be dangerous when its done with low altitudes. You have to carefully check that the radius is free from obstacles when you define the center position, altitude and distance from center (radius) for the POI flight. When POI is started it begins with comparably low speeds. You can modify the speed setting when the POI mode started. Unfortunately you cannot modify this stetting before you start. Tuning the speed on an iPad or (even more difficult – on an iPhone) is kind of dangerous because you easily move the slide too much to higher speeds than wanted and the copter will immediately accelerate and start circling your POI object like crazy until you managed to move the slider to slower speeds. There is however always this stop button to kill the POI mode – this is handy and needed sometimes. When you press the stop button the copter stops the POI mode completely and waits for new commands.

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