Topodrone DJI MAVIC 2 PRO L1/L2 PPK User manual

Topodrone SA
CHE-354.723.874 TVA
1820, Rue de la Gare 13, Montreux, Switzerland
[phone]
[email protected]
www.topodrone.org
TOPODRONE DJI MAVIC 2 PRO L1/L2 PPK
USER MANUAL

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 1 from 43
TABLE OF CONTENTS
No
Description
pages
1.
Drone preparation
2
1.1
First steps before work
2
1.2
Compass calibration
3
1.3
Camera calibration settings
4
1.4
IMU calibration features
5
1.5
GNSS receiver settings
6
2
GNSS data post processing and images geotagging
7
2.1
Data preparation
7
2.2
GNSS data postprocessing and images geotagging
7
3
Photogrammetry processing in Pix4D mapper
16
3.1
Creating a new project
16
3.2
Initial aerial triangulation
21
3.3
Camera calibration
22
3.4
Accuracy estimating
28
4
Photogrammetry processing in Pix4D mapper
4.1
Creating a new project, photos alignment
31
4.2
Accuracy estimating
35
4.3
Camera calibration
37
4.4
Aerial triangulation accuracy improvement.Tie points filtering
40
4.5
Removing rolling shutter distortion
43

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 2 from 43
1. Drone preparation
1.1 First steps before work
DJI Mavic 2 Pro Topodrone PPK – is a ready-to-fly geodetic survey solution which is based on DJI
Mavic 2 Pro drone. It is strongly recommended to learn DJI M2P manual first, you can find it on the official
web-site: https://www.dji.com/uk/mavic-2/info#downloads
Correct preparation of the drone means following exact rules to ensure flight safety and the best
orthophoto or 3D-model quality. Flight safety – is the main basis of all our solution.
1. Checking. All components of the drone must be in a condition: no damages, cracks or malfunctions.
It is needed to carefully inspect blades, motormounts, motors, arms, gimbal, micro-sd cards, cables
and connectors, especially if you had drone in a public use. Always check your DJI Mavic 2 Pro
Topodrone PPK before large orders and far business trips.
2. Charging. You should charge all batteries of the drone, remote controller (RC) and mobile device
up to 100%. Never use DJI Intelligent Battery which is charged lower than 90%, especially if battery
has started its storage discharging. It can cause premature termination of the flight mission.
3. Exploring. Before move to the working area, explore locality in a
on-line geo-services like DJI GEO, AirMap, and PilotHub, to
provide yourself more knowledge about places and objects located
nearby. It is not allowed to fly in No-Fly-Zones: airports, prisons,
sports stadiums. Military bases, state institutions, objects of
strategic importance (CHP, hydroelectric power plants, nuclear
power plants, etc.) are particularly dangerous, but they are not
marked at GEO-services. Electricity transmission lines, located at
the place you need to capture, can cause radio and magnetic
interference during the flight.
4. Setting. In the DJI Go 41 App set all parameters for comfort flying in a manual mode:
1. Distance limit – “turn off” value is recommended
2. Maximum Flight Altitude – 500 meters2 value is recommended
3. Return to home altitude – 100 meters or higher value is recommended. Anyway it changes
during the mission planning in the other apps.
4. RC MODE settings – changes axes of the sticks, value 2 is strongly recommended
5. EXP tuning – provides you control drone more accurate, 0.10 value is recommended
6. RC signal lost – action which drone would make if lost RC signal. Value “Return to home” is
recommended
7. Low battery warning – set at the minimum, 20% value is recommended3
NOTICE 1. DJI Go 4 App is the basic application for DJI Drones. You could not set several parameters
via other apps. It is recommended to make manual flights using DJI Go 4 App.
NOTICE 2. In some countries maximum allowed flight altitude for UAV is 120 meters. Setting 500
meters value in maximum flight altitude menu provide drone follow the terrain, flies higher than 120
meters from the altitude of home point, but not from the terrain.
NOTICE 3. If area of photographing is located far from you (more than 1 km), increase this value to 30%
NOTICE 4. Camera settings described in paragraph 1.3 of this manual.

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 3 from 43
1.2 Compass calibration.
As the basic model, DJI Mavic 2 Pro Topodrone PPK needs the compass calibration (CC) each time
you move to the new location. CC helps your drone to adapt to local magnetic field lines. During CC,
accelerometer and compass makes two rotations in different axes. After that, drone makes adjustment
between values of each sensors. To make correct CC follow next steps:
1. CC makes directly before flight at the open outdoor area. Making CC indoor is useless
2. Remove gimbal holder and unfold drone’s arms.
3. Turn on the drone and RC, insert and plug the mobile device.
4. Make sure, there are no large metal constructions or magnetic
fields in a 50 meters.
5. Enter drone into CC mode. At least there are two ways:
a) In the DJI Go 4 app open MC Settings / Advanced settings /
Sensors state / Compass / Calibrate compass / OK
b) At the right side of RC, rapidly move the slider to S and T
positions not less than 4 times.
6. Ensure that rear LEDs of the drone lights solid yellow.
7. Put RC in the left arm and take drone from the in your right arm.
Hold drone from the top under the battery. Do not change the
orientation of the drone!
8. Rotate drone to the left side (counter-clock wise) in 380 degrees
(a bit more than 360 degrees). Stop when the rear LEDs will
change color from solid yellow to solid green.
9. Change orientation of the drone, turning it in 90 degrees in a
longitudinal axis.
10. Rotate drone to the left side (counter-clock wise) in 380 degrees
(a bit more than 360 degrees). Stop when the rear LEDs will
change color from solid green to blinking green.
11. If using 5a way entering CC mode, turn the Flight Mode slider to
P (central position). This is especially important!
12. Compass calibration now is complete.
Before and after CC you can check the value of magnetic interference
in the DJI Go 4 App – it should be at the green zone after CC. If the app
notice you compass calibration failed (rear LEDs blinks red rapidly) – recalibrate compass at another place
nearby.
Notice 1: no magnetic or ferromagnetic objects on the body of pilot are allowed. For example:
massive jewelry, metal inserts or magnets in the end of the iPad tablet etc. If you have some of these objects,
even after successful CC, your drone will have “Compass Error” after taking off.
Notice 2: CC increase flight stability of the drone during the flight. But compass error can appear
even after absolutely correct calibration. It usually caused by different external interferences such are metal
objects, large antennas, electricity transmission lines (ETL)

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 4 from 43
1.3.Camera calibration and settings
Before the shooting process will be started, you should calibrate focus of your DJI Mavic 2 Pro PPK
camera and set optimal image settings. It is recommended to use next order.
1. You should determine drone’s working altitude. This value
depends on many factors: scale of the final orthophoto map,
properties of the lens, height of the obstacles, features of relief,
etc. Usually, working altitude is from 60 to 12 meters.
2. Set correct image ratio. Go to the image menu, tap the second
tab. Use the Image Ratio 3:2 value, it allows to use all square of
camera’s matrix. Do not use 16:9 Ratio! Check another values
of this menu – all defaults.
3. Lift off the drone to the working altitude and move gimbal to the 90 degrees (nadir). Ensure that
focusing method now is in the AF value. Then tap to the center of the screen to let the camera
focusing at the surface. After that change focusing method in the MF value - manual focus scale
will appear. Do not touch it! Now drone’s camera is focused at the selected height value. It will
not change in the future.
4. Now it’s time to set the best camera settings. All parameters are at auto as default. In this case,
drone will change image brightness, smoothness during the flight. But this way is bad for
triangulation image processing: key points at different images will be different. To get the best
image quality during the flight it is strongly recommended to set image params as follows:
ISO: from 100 to 200. Upper values increase image noise, and decrease ortophoto map quality
Aperture: from 2.8 to 4. Upper values decrease stream of light, so images will be darker
Shutter: from 1/1600 to 1/640. Upper values increase image motion blur, lower ones does not
allow the camera to get enough light, so images will be darker and more discolored.

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 5 from 43
1.4. IMU calibration and settings
IMU calibration needs very rarely. However some things can affect the sensor states: falls and
bumps, temperature changes and long stand by time. Because of use the additional module upper
the shell of DJI Mavic 2 PPK, the process of IMU calibration is
not the same as the default. To calibrate IMU you need to do
next:
1. Set up the props to motors
2. Fold the arms like at photo
3. Prepare your table or another flat surface: the horizon
should be aligned to the bubble level
4. Start the IMU calibration process and make steps 1-4 as
they are.
5. At step 5 you shoul place the drone head over heels. Use
the edge of table to make this step. Place your drone like
at the photo below
6. When the step 5 is complete, rotate drone and place it normally
7. IMU calibration now is complete

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 6 from 43
1.5.GNSS settings
Appearance and description of elements:
Green LED. Indicate power supply module.
Blue LED. Indicate quality of receive GNSS signal.
State
Description
No flash
PDOP>10
Slow blink
3<PDOP<10
Fast blink
2<PDOP<3
Solid blue
PDOP<2
Orange LED. Indicate recording data to a flash card. When recording in progress, LED rapidly blink.
Each blink means that 4 kB data is recording.
Red LED. Indicate, if system have error. In case of error, check flash card. If change, or install/format
microSD card not solved a problem, contact support.
Plug in microSD card.
Dual frequency (L1/L2) antenna

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 7 from 43
2. GNSS DATA POST PROCESSING AND IMAGES GEOTAGGING
2.1 Data preparation
Remove SD card with images from a drone and copy photos to your computer.
Divide a whole images dataset to separate flights and store photos from each mission in separate folders.
For example, Flight 1, Flight 2 etc.
NOTICE. Do not delete any images.
Remove SD card from GNSS receiver installed on the drone and copy ubx files to your computer to a folder
ROVER (for example).
Download GNSS static logs from a base station and convert them to Rinex format. Copy Rinex files to a
folder BASE (for example)
Mesure coordinates of ground control points (GCPs) and coordinates of the base station.
NOTICE. Coordinates of the base station should be in Latitude, Longitude, Ellipsoid high, WGS 84
coordinate system.
2.2 GNSS data post processing
Step 1. Run TOPOSETTER 2.0 application

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 8 from 43
Step 2. Select folder with photos

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 9 from 43
Step 3. Select UBX file from a drone

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 10 from 43
Step 4. Select Rinex or UBX file from a base station

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 11 from 43
Step 5. Impute coordinates of the base station in WGS 84.
Define antenna offset for a drone.
NOTICE.
FOR DJI MAVIC 2 PRO PPK use the following parameters
Height: 0.07
Offset forward/backward: -0.02
FOR DJI PHANTOM 4 PRO PPK use the following parameters
Height: 0.17

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 12 from 43
Step 6. Setup data processing setting. Click advanced setting. Advanced setting will appear.
To embed precise coordinates to photos EXIF tags check Burn exif check box. This option may lead
increasing of data processing time.
To save list of coordinates check Save text file check box.
Select format of text file Pix4D or Metashape
Click Save button.
NOTICE. To look at data processing performing switch on Display utility window option.
Click Start button

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 13 from 43
After finishing of all steps of data processing (data conversion, GNSS data post processing, images
matching and geotagging) all results will be stored in Output folder.
File Coordinates.txt is stored in PIX4D or Metashape folder
Photos with updated EXIF tags are stored in UpdateTags folder
Files with .pos extension are results of GNSS data postrpocessing
NOTICE. Coordinate system is WGS84.

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 14 from 43
Step 7. Checking processing results.
After processing accomplishing, the following buttons will appear.
NOTICE.
Click buttons in front of Rover or Base fields to open GNSS observation files to check the quality of
GNSS signal.
To check quality of GNSS data postprocessing click button in front of output results.

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 15 from 43
On the map you can see results of GNSS data postprocessing.
Green points of photos events – Fixed solution
Yellow points – Float solution
Red points – Single solution
NOTICE.
If there are only red points on the map it means, that GNSS data from a drone and a base station were
not collected at the same time.
If there are only yellow points (float solution) you should check coordinates of a base station or quality of
the signal. To remove noisy GNSS signal try to increase satellite mask angle or exclude GLONASS
satellite in Advanced setting menu.

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 16 from 43
3. PHOTOGRAMMETRY PROCESSING IN PIX4D MAPPER SOFTWARE
3.1 Creating pix4d mapper project
Run PIX4D mapper application.
Click New Project. Select a project folder location. Click next

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 17 from 43
Select images to be processed from output\UpdateTags folder. Click next

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 18 from 43
Software will read precise coordinates of images and accuracy setting automatically. Click Next.
NOTICE. It is possible to upload coordinates from txt file. Click From File button and select
coordinates.txt file
It is recommended to check camera settings. Cilck Edit button and check if Linear rolling shutter camera
model is enabled in case if DJI MAVIC 2 PRO was used for survey.

Topodrone SA
CHE-354.723.874 TVA
Rue du Centre 39, 1637 Charmey, Switzerland
[phone]
[email protected]
www.topodrone.org
Page 19 from 43
Select output coordinate system and click Next.