AERO RANGER FORUM

PILOT SUPPORT

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BY admin
#25
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Survey or "Area" missions are used to map a large area of terrain for use with orthomosiac and stitching products such as Pix4D. Typically, the drone will fly a "lawnmower" pattern of strips up and down a survey area, to produce a set of photos from which a map can be produced. The highest quality maps require flying low and using a cross hatch pattern of two interlocking "lawnmower" missions to produce good results and capture more detail.

NOTE: If you have a Spark you cannot use this mission. The Spark does not support waypoint missions.

Two main steps are required to produce a survey mission:
  1. Setting the mission objectives
  2. Define the survey area
First, navigate to the Plan screen using the main menu as shown below. Tap the "Hamburger" icon at the top left of the screen to display this menu:

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On the Plan screen, move the map close to the area that you would like to survey and zoom in to a comfortable level. Don't zoom in too far. While you can zoom and scroll later, it is easier to move the map to roughly where you need it first.

When ready to create the mission, press the round blue + button at the bottom right of the screen to reveal the mission selector. Tap on the "Survey" item and the tap Next to start building a Survey mission.

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Step 1: Mission Objectives

The objectives dialog for Survey missions has the most number of settings of any mission.

You can exit mission creation by tapping the X at the top left of the objectives dialog. This will cancel new mission creation and retain whatever mission is currently loaded.

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In the example above, there are several important settings that you can change, but in many cases the defaults will be suitable
  • Camera - The camera should show the drone that you are connected to now, or were last connected to.
    • Tap on this section of the dialog to display the camera settings.
    • In survey missions, only JPG photos or Video can be taken due to the short time between shots that is required. The camera will default to JPG even if you select RAW.
Tip: You don't have to change Camera settings now, you can change them at any time prior to takeoff. Camera settings are available from the main app menu

In a survey mission, there are two methods of setting the altitude. All waypoints in the mission will be created at the altitude you choose. As always, this is the altitude above the home point.

Either select the minimum GSD (ground separation distance) that you want, or select a fly at fixed altitude. Use the radio buttons next to each option to select and activate it.
  • Achieve minimum GSD - Using this option, the properties of the camera sensor are used to determine an alititude to fly at to deliver a required GSD.
    • GSD is expressed in cm/pixel and is the estimated coverage of a single pixel in the photograph
    • GSD is an approximation, on sloping terrain this setting will likely not be correct. It is based solely on the altitude above the home point.
    • The fixed altitude box below will be updated to show the altitude that this GSD would require.
  • Flying altitude (above home) - Use this option to simply enter an altitude you would like to fly at.
    • The GSD box will also be updated to show what this altitude will deliver in GSD terms.
  • Min Safe Alt - this is a critical setting for the entire mission.
    • Whatever other settings you choose, no part of the mission can be lower than this altitude.
    • It also defines the altitude at which the vertical part of takeoff finishes and the vertical part of landing begins
    • Make sure the Min Safe Alt is set well above any obstacles such as tall trees or buildings in your area of operations. The safety of the drone and people and property around you is your responsibility.
    • Remember - all altitudes are measured relative to the Home point.
  • Overshoot survey area - use this option to define a buffer zone around the chosen mission area to overshoot. This can help to avoid edge effects where there is not enough overlapping photos, but will increase flight time.
  • Crosshatch pattern - tick this to produce a cross hatched mission that is effectively two standard missions at 90 degrees to each other. This greatly improves the quality of the survey, and picks up features much better, but will double the flight time.
  • Sidelap % - The sidelap % defines the distance between each of the strips that the aircraft will fly (to the side), based on the camera properties and flight altitude.
    • The higher this value, the more strips will be flown. This can vary from 40% to 95%. 70% is a good default for most survey work.
  • Overlap % - This controls the distance between each photo along the flight line based on the camera parameters and flight altitude. It can vary from 40% to 95%. 70% is a good default for most survey work.
  • Target Speed - this is the speed in m/s that the aircraft will attempt to attain when flying the mission
    • If you set this too fast, you will be warned that the camera will not be able to keep up - either reduce the overlap % or reduce the speed. If you do not, the software will automatically set a lower speed.
    • If you set this too fast, you may not have time to react in case of an incident where you need to take manual control.
    • 5m/s=18km/hr=11.2 miles/hr
  • Gimbal Angle - Set the gimbal angle (0=horizontal, 90=straight down). In most cases survey missions require a 90 degree down angle, but you may change it here. Note that you will not have manual gimbal control during flight, so select the correct angle here.
  • Review mission after creation - if you tick this, the app will remain on the Planning page once you have finished creating the mission, if ticked off, it will automatically return to the Fly page, ready for takeoff.
Once you are ready, press Next.

Step 2: Define the survey coverage

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The next step is to set the coverage for the survey. In the current version of Aero Ranger, mission areas are rectangular only. There are plans to allow polygonal shapes in future releases.

A rectangular widget will appear on screen as shown. As with all missions, an instruction pane will also appear at the top of the screen. You can dismiss this at any time using the x at the top right.

Using the rectangular widget, you can size the survey area.
  • Pull on the round handles on each side to move that side in or out
  • With a single finger, you can drag the entire survey area around the map from the middle of the rectangle
  • With two fingers inside the rectangle you can pinch zoom to expand or contract the entire rectangle. You can also rotate it with two fingers.
  • The zig-zag line inside the box indicates the primary flight direction. If you have selected cross hatch, this is the way the drone will fly first, before rotating this 90 degrees for the cross hatch passes.
The length of each edge, and the overall survey area, along with an estimated flight time are shown on inside the rectangle. This flight time assumes a fixed landing/takeoff time component so use it as a rough guide only. Note that the mission details at the bottom of the screen will not be updated until the mission creation is completed and may show values from the previous mission, as in the above screenshot.

Tip: To zoom in/out and move or rotate the map, you can use regular pinch/zoom or single finger drag gestures on an area of the map away from the survey widget. 

Tip: If you have zoomed in too far, finger gestures may not work correctly. In this case, use the  Image button at the top right of the screen to zoom out one step.

Once you are satisfied, press the blue OK button at the bottom right of the screen.

Note: The actual size of the survey area may increase slightly when you press OK. The software sizes the rectangle to ensure a whole number of strips can be created, to avoid partial coverage along the edge.

A survey will be created as shown below

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In this image, the waypoint connecting lines have arrows to indicate the direction of flight in each segment.

Each waypoint is also numbered in sequence. The waypoints show their altitude (above the home point) on below the waypoint number.

If cross hatching was selected, the mission will look like this:

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In this example, the East/West lines will be flown first, followed by the North/South lines. The waypoint number indicates the order of flight.


Mission Statistics
After the mission is created, basic mission statistics are updated in the white strip beneath the map.

In the above case, the mission is 2.69km long, 179 pictures (estimated), 11:01 mins flight time (estimated) and will cover an area of 2.1 Hectares and 2.1cm per pixel

Final tips for Survey missions:
  • You can only fly a Survey mission with the camera set to JPG or Video. RAW mode does not work due to the short time between images that is required during surveying flights. RAW images cannot be taken any faster than once every 10secs. If you select RAW (dng), the camera will automatically switch back to JPG mode.
  • This camera gimbal angle is managed by the drone based on your settings in step 1. You won't have manual control over the gimbal during a Survey mission. In most cases it will point straight down.
  • The drone does not take terrain into account in any mission type. All altitudes are relative to the takeoff point. Please ensure you set the Min Safe Alt high enough to avoid crashing into terrain, buildings, people or infrastructure at any point of the mission. You are responsible for the safety of your equipment and people and property around you.
WHAT IS THE HOME POINT?

A critical part of any mission is the Home point.

SUPPORTED DRONE MODELS

Most recent DJI drone models are supported

HOW DO I CHANGE CAMERA SETTINGS?

Camera setting have recently had a major revamp.

How do I zoom the camera

To zoom your camera using AeroRanger

TRY OUT AERORANGER