DJI Matrice 4E / 4T mapping mission

For photogrammetry, use the wide camera on the 4E and 4T. Do not use the zoom or tele camera for the mapping grid, and do not mix cameras in the same job.

These are the wide camera figures from DJI's specifications:

Matrice 4E wide camera

4/3-inch CMOS, 20 MP, max image size 5280×3956, mechanical shutter (2 to 1/2000 s) and electronic shutter, JPEG or DNG (RAW)

Matrice 4T wide camera

1/1.3-inch CMOS, 48 MP, max image size 8064×6048 (12 MP or 48 MP photo modes), JPEG, no mechanical shutter listed

Note: The 4T also has a thermal camera. We do not use thermal images for processing. Upload only the visual wide-camera photos. Thermal images look like heat-colour pictures, so if the SD card folder mixes them with the visual photos, remove the thermal ones before you upload.

On the DJI Pilot 2 home screen, tap Flight Route, then Create Route, and create an Area Route. Tap the map and drag the boundary points so the area covers what you want to map. Tap the middle of a boundary point to add a new one.

Select the aircraft model, the camera and the lens. Choose the wide camera. Enter a task name and choose Ortho Collection for a standard map.

Set the following in the Area Route. The overlap values are the defaults DJI suggests for most scenes, and they match our other guides for orthophotos.

Altitude mode

Relative to Takeoff Point (ALT) is what DJI recommends for aerial mapping. Pilot 2 then asks for the target surface relative to the takeoff point.

Altitude / GSD

Pilot 2 shows the ground sampling distance (GSD) for the route altitude. A lower altitude gives finer detail, but more photos and a longer flight. GSD describes the level of detail, not absolute measurement accuracy. In ALT mode the altitude is measured from where you take off, not from the roof. Mapping a 30 m tall building from 50 m? The camera is only 20 m above the roof, so the overlap up there is much lower than planned. It is calculated for 50 m, not 50 - 30 = 20 m. If there are tall things in the area, fly higher or bump up the overlap.

Front overlap

80% (DJI default). Raise it if the area has large height differences.

Side overlap

70% (DJI default). Raise it if the area has large height differences.

Margin

Under Advanced Settings. The flight area extends beyond the mapping area, so the edges are photographed too.

Photo mode

Timed Interval Shot (the default).

Speed

Pilot 2 sets the speed from the GSD and front overlap, but check it anyway. The 4T wide camera has a rolling shutter, so photos smear more the faster you fly relative to your height. From experience: about 10 m/s from 120 m comes out fair, even over messy scenes. Fly lower, slow down in proportion: about 5 m/s at 60 m, 4 m/s at 50 m. If Pilot 2 wants to go faster than that, turn it down. The 4E has a mechanical shutter and is less picky, but flat out can still blur your photos.

Elevation optimization

DJI describes this as extra oblique photos taken from the middle of the area, and recommends it for orthophoto work. Optional. Not available with the Oblique Collection.

Note: Terrain Follow is available in the Area Route for areas with large height differences. To switch it on, choose AGL as the altitude mode. DJI describes Real-Time Follow, which uses the aircraft vision system and needs no DSM file. Terrain Follow keeps the height above ground similar, so the photo detail is more even across the area.

These are our recommendations for processing. Pilot 2 may already apply some of them in a mapping route, so check that they are set before you fly.

File format

JPEG. RAW/DNG is not needed for processing and makes the files much larger.

Image size

4:3 full camera frame. The Matrice 4E wide camera takes 5280×3956 photos. On the 4T, the photo size has to match what Pilot 2 planned the route for. Our 4T customers flying Pilot 2 mapping routes get 12 MP photos (4032×3024), and that works fine. Check the first photos on the card: 4032×3024 means you're good.

Distortion correction (dewarping)

Leave it off. DJI's manual says it is disabled by default in mapping routes.

Focus

DJI's manual says the default in mapping routes is manual focus set to infinity. Keep it.

Note: The Matrice 4E has a mechanical shutter on the wide camera. Check in the camera settings that it is in use for the mission. DJI does not list a mechanical shutter for the Matrice 4T wide camera. An electronic shutter reads the sensor line by line, so keep the flight speed moderate on the 4T.

Important: Before you start the mission, take one test photo with the wide camera and open its info or details. Check that the pixel size matches the full 4:3 size for your camera, and that the photo is not cropped. Do not rely on any setting being right without looking at a real photo.

For a 3D model, the Area Route in Pilot 2 has an Oblique Collection next to the Ortho Collection. Oblique Collection creates five s-shaped routes in the area and controls the gimbal to take straight-down and oblique photos in five directions.

Smart Oblique can be switched on in the Area Route. DJI describes it as a way to take photos from several angles by controlling the gimbal automatically. In the Oblique Collection, DJI says the aircraft only needs to fly one route to get the straight-down and oblique photos needed for 3D reconstruction. In DJI's manual, the default oblique gimbal angle is -45°, and the overlap of oblique photos can be lower than for straight-down photos.

Elevation optimization is not available together with the Oblique Collection.

DJI's manual says to enable RTK in the aircraft settings and wait for the RTK status to show FIX before collecting aerial photogrammetry data. RTK is a feature of the drone. We do not promise any accuracy of the result. If accuracy matters to you, check the result with your own control measurements in the field.

Save the task, then upload and run it from Pilot 2. Monitor battery and signal during the flight. The default action when the task completes is Return to Home.

When the mission is complete, land and power off the aircraft. Remove the microSD card and connect it to your computer. Copy all the visual photos from the mission to a folder.

Open the upload page, drop the folder in your browser, and choose orthophoto, 3D model, or both. Include all photos from the mission. Do not filter out photos manually.