Verify Position

In this segment, Marlyn’s GPS and Inertial Navigation systems are checked to ensure they are working before take-off. This will show the screen displayed.

Heading

This step is to check if the heading of Marlyn corresponds with the icon displayed on screen as shown. The belly of Marlyn, where the camera is pointing from, must have the same heading as the icon on screen (the arrow points in the direction of the camera). 

This is easily checked by pointing Marlyn to an object or feature that could be recognized on the map. Verify that the Marlyn icon points to the same object. 

You can also use a calibrated compass to check the heading by comparing the number in the icon to the compass.

Included with this checklist step is also a Passive check which determines whether the heading is drifting away from its current point. This is explained in further detail in this guide under ‘Heading Stability’. 


Position

For this step check verify that the position of Marlyn on the map corresponds with the position of Marlyn in the field.

Number of Satellites Connected

This is a Passive step which detects whether the number of connected satellites is sufficient for navigation. If the icons come up as light grey then the status is OK and no actions are required by the user, in any other case the sub-menu will display the errors as follows;

Status: Number of Satellites is larger than 9
Result: OK

Status: Number of Satellites is between 5 and 9
Result: OK, with warning message
RecommendationIt is recommended to make sure there are no objects above Marlyn and that the immediate vicinity is clear of large buildings

Status: Number of Satellites is less than 5
Result: Failed
RecommendationIt is recommended to make sure there are no objects above Marlyn and that the immediate vicinity is clear of large buildings

Accuracy

In this Passive step the Accuracy of the GPS fix is checked, which is known in surveying terms as the PDOP (Position Dilution of Precision). This is defined as the error caused by the relative position of the connected GPS satellites, and as such it is important to note that this number can be low even with an acceptable number of connected satellites. 

If the icons come up as light grey then the status is OK and no actions are required by the user, in any other case the sub-menu will display the errors as follows;

Status: PDOP is less than 1.7
Result: OK

Status: PDOP is between 1.7 and 2.4
Result: OK, with warning message
Recommendation: It is recommended to wait until the PDOP has improved before beginning the mission.

Status: PDOP is greater than 2.4
Result: Failed
RecommendationIt is recommended to wait until the PDOP has improved before beginning the mission.

GPS Fix

In this Passive step the overall GPS fix is checked and is a simple pass/fail. In order to get a fast and accurate fix, take the following aspects into account:

  • Step away from the aircraft
  • Position Marlyn at least 10 meters from electronic devices.
  • Do not attempt to start very close to high buildings or trees.

It might take up to two minutes from start up to acquire a GPS fix depending on the external conditions.

If the icons come up as light grey then the status is OK and no actions are required by the user, in any other case the sub-menu will display the errors as follows;

Status: GPS Fix OK
Result: OK

Status: GPS Fix Fail
Result: Fail
Recommendation: Make sure there are no objects above Marlyn and that the immediate vicinity is clear of large buildings

Heading Stability

This is a passive step in which the Heading as verified in the first step is not changing too greatly over time. Even after verifying the heading direction in the previous step, it is important to note that this number can drift by up to 90 degrees due to the presence of metallic objects nearby.

If the icons come up as light grey then the status is OK and no actions are required by the user, in any other case the sub-menu will display the errors as follows;

Status: Heading Drift within 5°
Result: OK

Status: Heading Drift between 5° and 15°
Result: OK, with warning message
Recommendation: It is OK to proceed, but ensure not too much time passes by between now and the take-off to prevent the heading from drifting further. 

Status: Heading Drift Greater than 15°
Result: Failed
Recommendation: Reboot Marlyn at a different location, away from possible ferro-metallic objects close by. 

Once all of these checks are complete, press ‘Next’ to proceed to the next segment.