Hardware - Geometrics Forum

Finding lost MagArrow II with a new MagArrow II

Muhammad Devandra — Wed, 24 Sep 2025 05:27:48 +0000

Hello everyone, my name is Devan, and I would like to open a discussion about finding a lost MagArrow.

To give you some background, I lost my MagArrow II while it was mounted below the DJI M400 during a flight mission in a highly dense forest. We have the drone flight log, which indicates that it was stuck in a tree within a 50 m radius of the last known location. We have searched the whole area, but due to a highly dense forest and steep terrain, it was very difficult to find the MagArrow II and the drone on foot.

For more than a month, I presume it was still perched within the tree canopy. And now we have bought a new MagArrow II to continue our survey. In this case, I desperately want to find and retrieve the lost MagArrow using the new device.

I have an idea that if I conduct a 5 m spacing grid in both East-West and North-South directions within a 100-meter radius of the last known location, we could eventually narrow down our perimeter by finding an anomaly that indicates the lost device. Therefore, I have a few questions:
1. How magnetic is the drone and the MagArrow II?
2. Is it feasible to find the old MagArrow with the new MagArrow with the stated method? Alternatively, do you have any effective suggestions for a different approach?

I appreciate any insights you can provide. Thank you!

SD problems

Charles Yago — Wed, 30 Apr 2025 15:55:12 +0000

hello :)
Im having problems with MagArrow II data recording, and i'd love some help or advice.
The issue definatly is a problem with the SD connection. Im having no troble connecting to the sensor's WIFI, but when heading to the "Data" page I get the massage "Unable to load servays. Verify that the SD card is insrted correctly. " Indeed in systemtest page i get a "SD card: Failed" test.

Im aware of the SD's spring load mechanism, and tried many times in different configurations, including trying with different SD cards, updating the MagArrow software, but to no avail. The system just wont recognise any SD :(

Anyone had a similare problem? Any tips or suggestions?
I'd love to get the sensor working again

Takeoff and Landing with a Tethered MagArrow

Gretchen Schmauder — Tue, 21 Jan 2025 20:46:02 +0000

The following video shows the correct way to takeoff and land with MagArrow II tethered to the drone. Takeoff and Landing

microSD card type and format

Rui Zhang — Mon, 13 Jan 2025 17:35:44 +0000

We suggest using microSD cards with specs equivalent to or better than SanDisk Extreme and format it to exFAT.

Why does data transfer through WiFi become slow?

Rui Zhang — Sat, 27 Jul 2024 01:19:26 +0000

If the system has a large amount of survey data, it may affect the data transfer rate. Sometimes a very slow SD card makes the system unresponsive; to the user this can look like a slow/bad network connection. Therefore, it might be useful to clean up the SD card and USB drive.

1. Delete the Geometrics.log file on the USB drive.

1. Clean up the survey data on the SD card:

1. 1. First, make sure that you have all the data that you need off of the SD card. Either download all survey data that you want to keep, or copy all of the contents of the SD card to another drive (perhaps to a PC).

1. 1. Delete all of the data on the SD card, doing one of the following:

1. 1. 1. Use the UI to delete all of the surveys, then use the "Clean old files" button on the Admin page to empty the recycle bin on the SD card. This can be VERY slow, and because the MagArrow has a very simple web interface, the user will get no useful feedback. On a very full SD card, this process might take 30 minutes or so.

1. 1. 1. Or.... Remove the SD card from the MagArrow and after copying any data that the user still hasn't saved to a PC, format it or delete everything on it, then re-insert it. Be careful not to lose the SD card or to let it drop into the inaccessible spaces in the instrument. If you format the SD card, the ExFAT format is preferable.

If the customer can't get the data downloaded from the instrument (takes too long or stops), the data can be imported into a survey in Survey Manager, directly from the SD card (or from the PC hard drive to which the SD card data has been copied). Then the SD card can be cleaned up or formatted.

With the new version of Survey Manager (you need to update that also, not just the instrument software), the user can import a large survey, including all of the files in subdirectories, by selecting the "acquinfo.txt" file in the root directory of the survey, from the SD card.

More details about how to import/export SD card files using Survey Manager can be found in the post below:

SD card files conversion

A simple mounting configuration to improve MagArrow stability during flights

Rui Zhang — Wed, 08 May 2024 16:36:53 +0000

Many of our customers have found out that widening the attaching points of a MagArrow can greatly improve its stability (reducing swings) during flights.

If you are interested in designing a customized mounting fixture, a CAD file of a MagArrow baseplate can be found here: https://www.geometrics.com/community/magarrow-hardware/half-rigid-suspension-design/#post-1154

Make MagArrow tow/suspension cables in different lengths

Wei Jiang — Tue, 07 May 2024 14:59:19 +0000

Geometrics provides MagArrow tow/suspension cables with 10ft length. Customer can make their own tow/suspension cables in different lengths. See the attached zip file for instructions on how to make MagArrow tow/suspension cables. It contains a procedure, a Bill of Material, and some construction notes in a ReadMe.txt file.

Why does it take so long for my MagArrow GPS to lock?

Rui Zhang — Mon, 25 Sep 2023 20:22:10 +0000

1. Make sure the MagArrow top cover (the curved side) is facing up and under a clear sky.

2. It may take up to 20 minutes for the GPS to lock during the initial power up. Afterwards, the GPS stores the location information for a while (~40 minutes for MagArrow I and ~ 2 hours for MagArrow II) without the power so that it can lock much faster than 20 minutes (~2-3minutes) during subsequent powerups.

3. If the powerup locking time is significantly longer or intermittent GPS dropouts are observed during flight:

MagArrow I will need to be sent back to Geometrics for repair.
MagArrow II customers may choose to unscrew the external helical antenna (or attach the external helical antenna) and check whether the longer-than-normal locking time or the intermittent issue goes away. MagArrow II has an independent internal and external antenna design. When the external helical antenna is attached (unattached), the system switches to the external (internal) antenna automatically.

Frozen compass readings

Rui Zhang — Wed, 20 Sep 2023 19:17:53 +0000

1. If the frozen issue is intermittent, please update to the latest MagArrow embedded software and survey manager, which can be found in the download section of MagArrow. The compass status can now be monitored on the browser interface. If the compass fails, power cycle the MagArrow.
2. The frozen issue often occurs during the startup when the MagArrow faces exactly north/south/west/east. The compass initialization sometimes fails when one of the compass readings is close to 0. The latest embedded software greatly improves the robustness of the startup procedure. However, if the frozen issue persists, please power up your MagArrow facing north-west.
3. If the above two steps do NOT fix the issue, the MagArrow has to come back for repair.

Half Rigid Suspension Design

Rui Zhang — Thu, 07 Sep 2023 01:09:14 +0000

With the provided 10-feet suspension cables, the magnetic noise due to most commercial drones can be ignored. However, some MagArrow customers experience stability issue, especially in windy conditions.

For a small number of drones, the MagArrow can be attached to the landing gear directly with acceptable noises (line-levelling is still required in data processing).

For most drones, however, this configuration causes too much noise. A half rigid mounting design may solve this problem. It has 2 rigid bars with hinges on one side and 2 flexible cables on the other. On the ground, the rigid side folds to the side. While in the air, gravity will keep the MagArrow further away from the drone. Drone noise can be greatly suppressed since the noise follows 1/R^3. A factor of 2 increase in the separation can lead to a factor of 8 decrease in noise.

Please make sure the hinges and the rigid bars are made of non-magnetic material.