CAVU FPV for DJI Go Drones

CAVU is an acronym used in aviation circles meaning "Ceiling and Visibility Unlimited." Commonly used by pilots as slang to describe anything that is desirable or sought after.

(http://www.urbandictionary.com/define.php?term=CAVU)

1.1 What is needed?

What is needed to run this app:

a DJI drone (Phantom 3 or newer); if you want to use a Phantom 3 Standard, please read this
a smartphone running Android 4.4 or newer and a high resolution (at least Full HD = 1920*1080 pixels, better Quad HD = 2560*1440 pixels or 4K, see "The math" below)
VR/3D goggles

e.g. "google cardboard" compatible
please note that Samsung Gear VR goggles cannot be used because on older models it is not possible to connect the smartphone to the remote controller via USB - the USB port is blocked by the Gear VR; on newer models an USB port exists, but the connection fails)

Why Android?

To experience the first person view with a VR headset, it is cruicial to have as many pixels as possible.
The 5.5" versions of the iPhone currently only have Full HD which is not optimal for a good flight experience (we recommend using devices with Quad HD or 4K).

The math:

Full HD = 1920 * 1080 = 2,073,600 pixels
Quad HD = 2560 * 1440 = 3,686,400 pixels = 1.77 times the pixels of Full HD
4K = 3840 * 2160 = 8,294,400 pixels = 4 times the pixels of Full HD

1.2 What are we recommending?

During the app development we found the following hardware to be recommendable:

drones

the Phantom 4 Pro (without the built-in monitor)

the endless number of sensors make flying as easy as never before
the superb 20 mega pixel camera takes stunning fotos
the ability to control the yaw of the camera/gimbal via head tracking

the Mavic Pro

for its mobility and "ready to fly" time

the Spark

for its completely wireless operation (no USB cable required between remote controller and smartphone)

Android smartphone

Samsung Galaxy S8(+)

superb display (Quad HD)
good camera (for "ground view")

LG G6

currently the most affordable of the 2017 "flagship" devices with a very good display (Quad HD+)

Sony Xperia XZ Premium

has the best display of any smartphone (4K resolution - double the resolution of the dji goggles)
unfortunately some "tweaks" are needed to activate full 4K support
read more

VR goggles

3D/VR goggles that allow to adjust the eye distance and that allow you to keep your glasses on
in case your smartphone does not have a very high resolution, you can try "non-VR goggles" instead

flexible USB cables
in case you are using the Phantom 3 standard, you can use Bluetooth remote/game controllers to take photos and record videos

1.3 Where to download

The app can be downloaded in Google Play store.

Please note:
Although the app can be downloaded and tested for free, an in-app-purchase is needed to unlock the "flight time restriction".
Please read this for more detailed information.

1.4 What's new? (Release notes)

You will find the information about the latest features in our Release Notes document.

The "Closed" items in the list are already available.

The "Active" items are currently in development.

The "New" items are planned to be realized in the near future.

1.5 App languages/translation

The app is currently translated to German and English only (the documentation is available in English only).

We don't want to use automatic translation services because we think the result is not optimal (and looks funny/strange in some cases). Using professional translation services for all languages is beyond our budget.

If you want to see the app in your native language anyway, you can support us to translate it - it's around 125 labels/short texts to translate (excluding the help pages).

2 Who are we and what is our mission?

We are a small group of passionate software developers (usually working for corporate companies and on our AirPlay Multiroom audio solution/app).

We are in the RC hobby for quite a while, mainly cars and helicopters.

In 2016 we were infected by the "drone virus".

Not satisfied with the (fpv) controller apps available, we decided to do something about that...and started the development of our own controller app.

Because the result is quite good and we wanted to share our love of flying fpv, we decided to publish the app on the Google Play Store.

Our mission is to provide the best flying experience (flying is fun!), without loosing the feature of taking great pictures and videos while on the flight... For us a 100% stable and easy to use app is more important than a feature-overload.

If you have ideas how to further improve the app or you are experiencing problems with our app, please contact us via the "Contact/Feedback" button in the main menu of the app. Alternatively you can send an email to the address linked in the Google Play Store.

We usually answer within 2-3 days.

If you want to see what we are currently working on, please have a look at our Release Notes and Beta Program.

3 Starting the app

After downloading the app from Google Play store, it's time to start the app for the very first time.

Some things are to consider which are described a bit more in detail in the following sections.

3.1 Android 6 and app permissions

In order to make the app run properly, some permissions are needed.

Apps developed for Android 6 (M) or newer have to request these permissions explicitly.

When you start the app for the very first time, additional dialogs will be opened that will ask you for the permissions individually.

The following permissions are needed:

Make and manage phone calls - The SDK provided by DJI needs this permission to get a unique device identifier. Neither phone calls are started, nor your contacts are read. All DJI compatible apps (incl. the DJI GO app) need this permission. But apps that are developed before Android 6 won't show that explicitely.
Take pictures and record video - This is used to show the pilots perspective.
Access this device's location - This is needed to calculate the home position of the drone.
Access photos, media, and files on your device - To store temporary data and log files.

Additional information can be found in our privacy policy.

3.2 The main menu

The first thing you will see (after accepting the permissions) is our main menu.

Here you have access to the main functions of our app:

the VR flight mode ("GO FLY")
access the help (this document)
access to information how to deal with USB connection problems
the possibility to contact us and give us feedback
the possibility to unlock the flight time restriction (only visible when a drone is connected)

3.3 Potential USB connection problems

If you have installed multiple DJI compatible apps on your android device and you connect it to the DJI remote control via USB, a dialog will pop up asking for the app to use.

When you select the app, please always press "Just once" or deselect the "Use as default app" checkbox.

Otherwise the selected app is always started whenever the cable is connected.

The other apps will not be able to connect to the drone in this case.

If you pressed "Always" accidently, we added some features in the app how to solve this problem easily.

Have a look at "Help for USB connection problems" in the main menu.

If the message "Unfortunately, System-UI has stopped." appears, this is the result of a bug in the Android 6 operating system. In this case, NONE of the DJI app will work any more.

We experienced this problem during testing with the LG G4 smartphone on Android 6.

Unfortunately, the only "solution" in this case is to have installed max. one DJI compatible app at the same time.

Sorry for that!!

4 Demo mode and in-app-purchases

Bad news first:

This app is not free.

Developing and maintaining software is very time consuming - and with that very expensive.

The good news:

You don't have to buy a pig in a poke.

You can download the app for free.

It will run in "demo mode" - which means you can fly your drone using our app for 5 minutes on each app start.

After 5 minutes of flight, a semi transparent overlay will appear over the flight screen telling you the flight time is over.

You will still be able to fully control your drone and also see the live-view image.

If you like the app, we would be happy if you share it with your friends.

The more people downloading (purchasing) the app, the more time we can invest to further improve it.

5 VR Flight Mode ("GO FLY")

The "VR Flight Mode" is the main feature of our app.

It allows you to use your smartphone together with VR goggles as a FPV headset.

For this purpose, there are 2 images shown side by side.

The following sections will describe how to handle the vr mode and how to configure it according to your preferences.

In case you forgot your vr goggles at home or want to fly without them, we added the possibility to switch to "traditional" layout.

5.1 On-screen help/tutorial

We tried to make our user interface as self-explanatory as possible.

For this reason we added some tutorial overlay on the flight screen.

It will give you hints what to do - especially when using the app for the first time.

5.2 The configuration menu

Depending on the flight mode, the configuration menu is either at the top of the screen or on the right hand side.

How it can be used to adjust the user interface to your needs is described in section Configuring the user interface.

When you are in VR mode and the smartphone is inserted into the vr goggles, the menu is hidden automatically (using the proximity sensor).
In non-vr-mode the menu can be hidden by pressing the menu button in the top right corner.

5.2.1 Controlling the camera gimbal via head movement

Usually, the camera gimbal is controlled with the wheel on the upper left side of the remote controller.

To allow a more immersive flight experience, the app gives the possibility to control the gimbal via head movement.

To enable/disable this feature, tap the corresponding icon in the configuration menu once the drone is connected (after installation of the app, this is enabled by default).

The app allows the control of the gimbal pitch within a 120° range (-90° down; +30° up) for almost all of the dji drones.

The Spark only supports a 90° range (-90° down; 0° up).

For drones of the Phantom 4 product range (Phantom 4 standard, advanced and pro) it is also possible to control the horizontal movement (yaw) of the gimbal by rotating your head.

Please note

Although this feature works for the dji Mavic together with the dji goggles, this is not possible for 3rd party apps - we are currently trying to contact dji...

To make this feature work, you have to define a "center" direction.

You can do this by pressing and holding the c1 button on the remote controller for 1.5 seconds while you are in flight screen.

Once a center is defined, a small triangle will appear in home point and drone location display.

This triangle indicates the direction of the gimbal in relation to the drones front direction/orientation.

Moving your head to the left/right will rotate the camera/gimbal accordingly.

Please note:

The process of defining the center position has to be done after each launch of the flight screen.
If you don't want to control the yaw, simply skip the process.
To reset the "center" position during flight, repeat the process of pressing and holding the c1 button at any time.

5.2.2 Enable/disable HD live video image

On some devices there is a delay/latency of the live video image.

This potentially comes from using slower smartphones that cannot handle the high resolution video preview images very good.

To support also slower devices, it is possible to activate/deactivate HD live video transmission.
For this purpose you will find a "HD" button in the configuration menu. Tap it to enable/disable HD live video transmission.

5.2.3 Switch off VR goggles mode

You forgot your VR goggles at home? Or you are just not in the mood to fly vr?

No problem, simply switch back to the "traditional" view.

To enable/disable the goggles mode, simply press the goggles icon in the menu.

You can define the layout for goggles and non-goggles mode individually.

5.3 Showing live preview image

You can toggle the images by pressing the c1 button.

5.3.4 Zoom the smartphone view & toggle focus mode of smartphone camera

When you are in "ground view" mode (the picture of the smartphone camera is shown) you can use the right click wheel on the remote control to zoom in and out the picture.

With that it is possible to watch the drone from the ground even it is a bit further away.

If you click the right wheel, you can toggle the focus setting of the smartphone camera.

If you are using the Mavic Drone:

push the "5D-pad" up and down to zoom in/out
use the c2 button to toggle the focus
this also works for the "drone" view - you can zoom the picture + set the focus manually

5.4 Flight data displays (HUD)

During flight various flight data displays (head up displays / HUD) are shown.

These displays are described in the following sections.

If you tap an item on the screen, a short description of the item will be shown in the Important messages display.

The layout/position/size of these items is fully adjustable.

5.4.1 Signal strength

The signal strength display shows the quality of the video transmission signal between the drone and the remote controller.

If the strength is below 40%, the display gets yellow to indicate warning.

If the strength is below 20%, the display gets red to indicate a critical warning.

5.4.2 Height, distance and speed

There are 2 blocks of displays showing height, distance and speed related information.

The upper display of each block shows the height/distance of the drone in relation to the home point.

The lower display of each block shows the corresponding speed (rate of ascent/descent and horizontal speed).

5.4.3 Flight time and battery status

In the top center you will find the information about the flight time with the current battery pack.

In the bottom center you will find the information about the remaining battery capacity (in percent) and the estimated remaining flight time.

The remaining battery display will turn yellow if the battery capacity drops under 50% to indicate warning.
If the capacity drops below 30%, the display will turn red to indicate critical warning.

5.4.4 Google maps display

With the Google Maps headup display you will know exactly where you are - all of the time.

You can enable/disable the display using the Google Maps button in the configuration menu.

You can resize and move the display together with the other HUD as described in section "Configure the flight data views".

The following information are shown

in the drone perspective

the current drone position (if known) = center
the direction the drone is heading to = top
the home point (if locked)
a connection between the drone position and the home position

in the ground perspective

the current smartphone position (if known) = center
the direction the smartphone/vr headset is heading to = top
the current drone position (if known)
a connection between the smartphone position and the drone position

5.4.5 Home point and drone location

The home point and drone location display has multiple purposes/states

when no drone is connected, it shows a red circle which is striked through
when a drone is connected, but the home point is not locked, it shows a red circle and the drone
the drone symbol is pointing into the direction the camera is facing to (top = north)
if the home point is locked the circle turns green
it stays green as long as the drone is within a 5m range around the home point
the circle is yellow as long as the drone is outside the 5m range but inside a 10m range around the home point
if the drone is outside a 10m range around the home point, the circle will be replaced by an arrow pointing into the direction of the home point

5.4.6 Photo and video recording state

During video recording, the display in the top left corner shows the duration of the recorded video.

If a foto is taken, the display in the top center shows the number of the foto (since the last start of the app).

Both displays are only showed when needed.

5.4.7 Important messages

If during flight something important happens that is not shown/indicated by the flight data displays, it is shown in the "important messages" display.

If during configuration mode a flight data display is tapped, the information message display will show a short description of the display.

6 Taking fotos and recording videos

6.1 Taking photographs

To take a photograph, press the shutter button on the top right of the remote controller.
Fotos are taken in the highest available resolution with a 4/3 aspect ratio.

The foto HUD will show the number of the foto for 2 seconds.

6.2 Recording videos

To record a video, press the record button on the top left of the remote controller.
Videos are taken in 4K resolution with a 16/9 aspect ratio.

The video recording state HUD will show the length of the video during recording.

6.3 Take photos and record videos using a bluetooth remote/game controller

The DJI Phantom 3 Standard does not have any additional/custom buttons on the remote controller to take photos or record videos.
This makes it hard to achieve these tasks when the smartphone is used in the VR headset.

To allow to take photos/record videos anyway, CAVU FPV allows to use Bluetooth game controllers to trigger the actions.
What you need is some kind of Bluetooth game controller, e.g. this one.

Please connect the controller to your phone using the Android Bluetooth settings as described in the user manual of the game controller.
If the controller supports multiple modes (mouse, keyboard, game controller), please make sure it is set to game controller mode.

Once it is connected, you can start CAVU FPV.
In the flight screen you will see a bluetooth icon.

This button has the following states/actions

By default, the button is deactivated (light gray).
If you press it and no game controller is connected, you will get a corresponding information.
If you press it, you need to configure the controller-buttons you want to use for taking photos and recording videos. Please follow the instructions on the screen.
Once the buttons are configured (and a controller is connected), the UI-button will turn white. You can use the controller-buttons to trigger the actions.
If you press the button while it is white, you can stop/reset the configuration.

7 Configuring the user interface

The user interface is fully adjustable and can be configured to fit your requirements.

The following sections describe how this can be done.

7.1 Adjusting the eye distance

If you cannot see the text of the flight data displays clearly, maybe the eye distance is setup incorrectly.

If your vr goggles support it, please first try to adjust eye distance in the goggles itself.

If that is not sufficient, you can use the eye distance button in the configuration menu.

If the setting is active (the button becomes white) you can adjust the distance by dragging the preview image to the left/right.

7.2 Move the live view image

By default, the live image is shown in the center of each eye so that it is completely visible.

By pressing the adjustment button in the configuration menu, you can adapt the position and size of the live image according to your wishes.

Simple drag the view to the desired position and use the 2-finger-zoom-gesture to adapt the size.

7.3 Move the second (PiP) display

By default, the PiP image is shown on the left hand size of each eye so that it is out of the way but still visible.

By pressing the adjustment button in the configuration menu, you can adapt the position and size of the PiP image according to your wishes.

Simple drag the view to the desired position and use the 2-finger-zoom-gesture to adapt the size.

The section Picture in Picture (PiP) mode describes how to enable/disable the PiP mode.

7.4 Configure the flight data views

We positioned the flight data displays / HUD in a way we think it makes sense.

But as the other views the location and size is fully adjustable.

By pressing the adjustment button in the configuration menu, you can adapt the position and size of the HUD according to your wishes.

Simple drag the view to the desired position and use the 2-finger-zoom-gesture to adapt the size (of all displays simultaneously).

7.5 Switching between metric and imperial units

By pressing the units item in the flight screen (showing "km/h" or "mph" depending on your current setting) you can switch between metric and imperial units.

8 Special hardware

This section describes some "special" hardware that limits or extends the default features of the app (or that require additional skills to get it working as desired).

8.1 The Phantom 3 Standard

The remote controller of the Phantom 3 Standard does not have any additional (custom) buttons to be used by apps.

The Phantom 3 standard can be used with our app anyway, but there are some limitations/changes to the standard behaviour of our app.

most of the tutorial screens shown when first using the app are deactivated
it is currently not possible to switch between drone and ground perspective (missing c1 button on the remote controller)
taking fotos and recording videos is not possible by default

using an additional bluetooth remote/game controller can solve this problem; see here

8.2 Sony Xperia ZX Premium - 4K smartphone

The Sony Xperia ZX Premium has an outstanding feature that makes it perfect for VR/fpv purposes - a 4K display...

... in theory.

Unfortunately Sony decided that the usable resolution for 3rd party apps is locked to Full HD (1920*1080) by default - with the exception of some media content.

We already requested a feature that allows 3rd party apps to activate 4K resolution in the Sony forum - without success so far..

To be able to use the full 4K resolution anyway, some "tweaks" are needed.

you have to enable "Developer mode" on your android device - see here how that works
you need to download the Android Studio development environment by google - see here
connect your Android device to your PC via USB cable
open a command line in the directory sdk\platform-tools
in the command line, type "adb shell"

enter "wm size 2160x3840" to switch to 4K resolution
enter "wm density 800" to adapt the size of the icons to a reasonable size
see this forum for details

now you can run CAVU (and all other apps) in 4K
to switch back to default resolution, please

enter "wm size 1080x1920" to switch to Full HD resolution
enter "wm density 400" to adapt the size of the icons to a reasonable size

Please note that the Sony Xperia X5 Premium already had a 4K display - but due to a slow processor we do not recommend using it in 4K mode.

8.3 Quanum DIY FPV Goggle V2 PRO (non-VR)

If your smartphone does not have a high resolution but you want to try flying fpv anyway, you can try the Quanum DIY FPV Goggle V2 PRO, some non-VR goggles.

Compared to other VR headsets, this uses a single lens - both eyes will see the same display. With that, no 3D effect is possible - but the full resolution of the smartphone display can be used for both eyes.

It cost around 30-60$ and comes with a 5" TFT monitor.

You can replace the monitor with your smartphone easily.

By switching off the VR mode in CAVU this goggles can be used with the app.

Please note that the fpv experience is a bit less immersive than with other devices, but it's a good compromise for smartphones with lower resolution.