# GPS Glitch on HERE4 blue (DroneCAN) during Pre-Arm – persists after module replacement

**URL:** <https://discuss.cubepilot.org/t/gps-glitch-on-here4-blue-dronecan-during-pre-arm-persists-after-module-replacement/17737>\
**Category:** Here GPS\
**Created:** [23 July 2026 18:02 UTC](https://discuss.cubepilot.org/t/gps-glitch-on-here4-blue-dronecan-during-pre-arm-persists-after-module-replacement/17737 "2026-07-23T18:02:26Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Mandelo](https://discuss.cubepilot.org/user_avatar/discuss.cubepilot.org/mandelo/32/9767_2.png) [@Mandelo](https://discuss.cubepilot.org/u/Mandelo)\
**Post date:** [23 July 2026 18:02 UTC](https://discuss.cubepilot.org/t/gps-glitch-on-here4-blue-dronecan-during-pre-arm-persists-after-module-replacement/17737/1 "2026-07-23T18:02:26Z")

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## 

[2026-07-22 16-01-19.bin](https://discuss.cubepilot.org/uploads/short-url/38P6izfL58WANdFdiHqHZ7to8VT.bin) (4.4 MB)

## Description

I am experiencing persistent **GPS Glitch errors during pre-arm** , even with the vehicle completely stationary on the ground.

This issue **was already present before replacing both HERE4 modules** , which is why they were replaced in the first place. After replacement, the behavior remains exactly the same.

* * *

## Setup

- Flight Controller: Cube Orange+

- Firmware: ArduPilot 4.5.7

- GPS: 2x HERE4 (DroneCAN)

- Configuration:

- Environment:

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## Observed Behavior

- GPS Glitch occurs **during pre-arm (no movement, no vibration)**

- Happens consistently after boot

- EKF rejects GPS even though solution appears valid

### GPS Data (GPS1)

- HAcc: ~0.8 m

- VAcc: ~1.4 m

- SAcc: ~0.15 m/s

- No major degradation in accuracy

- Occasional message delay spikes (~400 ms)

### PM (Performance Monitor)

 ![newplot (20)](https://discuss.cubepilot.org/uploads/default/original/2X/0/09486e4f5228c431148089c085e9005951aa5d74.png)

- No scheduler overruns (NLon = 0)

- No internal errors

### CAN

- No bus errors

- No overflows

- No packet drops

### However:

- Significant **Clock Drift (~ -200 ms)** observed

- 

- Loop rate appears to drop during glitch events (from ~400 Hz to ~20 Hz in plots)

 ![newplot (18)](https://discuss.cubepilot.org/uploads/default/original/2X/e/e0932a976433d1428f8bb1128abad94e278cd6a0.png)

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## Observations

- GPS data quality is good

- No indication of GNSS reception issues

- No CAN errors

- CPU overload

- Problem occurs even when stationary

- Replacing both HERE4 modules did **not** solve the issue

- Another identical drone (same hardware/config/location) works normally

* * *

## Tests already performed

- Replaced both HERE4 modules → no change

- Verified GNSS quality → good

- Compared with identical drone → no issue on other unit

* * *

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---

<div class="post-metadata">

**Author:** ![xfacta](https://discuss.cubepilot.org/letter_avatar_proxy/v4/letter/x/5f8ce5/32.png) [@xfacta](https://discuss.cubepilot.org/u/xfacta)\
**Post date:** [30 July 2026 23:09 UTC](https://discuss.cubepilot.org/t/gps-glitch-on-here4-blue-dronecan-during-pre-arm-persists-after-module-replacement/17737/2 "2026-07-30T23:09:24Z")

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A quick check of the log, I would say it’s an issue with compasses. There’s possibly some large electrical fields in the roof of the building you are on.  
I would go to an ordinary field and do a compass calibration then re-assess.  
I dont see anything wrong with the GPS units.  
“Glitch” just means the GPS position doesnt agree with the IMU and compass inputs.