Bug: T-Echo (nRF52840) on 2.7.15 reports incorrect and quantized GPS positions

[4cnmpj8ry6-ops]

Category

Other

Hardware

T-Echo

Is this bug report about any UI component firmware like InkHUD or Meshtatic UI (MUI)?

• Meshtastic UI aka MUI colorTFT
• InkHUD ePaper
• OLED slide UI on any display

Firmware Version

2.7.15.567b8ea

Description

Hardware:

• LILYGO T-Echo (nRF52840)

Firmware:

• 2.7.15 (commit 567b8ea)

Observed behavior:

• The GPS coordinates shown on the T-Echo e-ink display are wrong by ~200–300 meters (mostly in longitude)
• Multiple different nodes appear at exactly the same coordinates on the Meshtastic map
• This happens even when nodes are physically separated by tens or hundreds of meters
• Position overrides, reboots, and moving the node outside do not change the offset

Additional observation:

• ESP32-based nodes running the same firmware in the same mesh show distinct positions, while multiple T-Echo nodes collapse to the same map location

This looks like a problem in how GPS positions are encoded or transmitted on the nRF52 (T-Echo) platform rather than a reception or multipath issue.

Steps to reproduce:

1. Flash a LILYGO T-Echo with 2.7.15
2. Place two T-Echo nodes 50–200 m apart outdoors
3. Both nodes appear at the same or nearly the same coordinates on the map

Expected:
Each node should show its actual GPS position.

Relevant log output

[github-actions[bot]]

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[fifieldt]

https://meshtastic.org/docs/configuration/radio/channels/#position-precision

[4cnmpj8ry6-ops]

The position precision value, doesn’t look available in the iPhone Meshtastic app. Due to lack of knowledge and possibilities I don’t see other methods to set the value

[4cnmpj8ry6-ops]

Let me try to explain: on the node map there are two clusters of nodes. My node is part of the most eastern cluster and it is about 700 meters east of my home. When I zoom in to that cluster, I see many nodes, currently 6, including nodes of which I know the position, one is north of me and one northwest of me. All the 6 nodes have exactly the gps longitude and latitude. This both appears on the screen of the t-echo as well on the iPhone app.

[b8b8]

The position precision value, doesn’t look available in the iPhone Meshtastic app. Due to lack of knowledge and possibilities I don’t see other methods to set the value

It's under the channel settings. You need a private primary channel or disabled position on longfast to enable precise location on private secondary on iOS. By default, imprecise locations are shared and you need to change it to precise. The way positions are made imprecise is by dropping bits. This causes all the close by nodes without precise position to appear to be at the same spot.

[4cnmpj8ry6-ops]

Thank you for explaining the functionality, conclusion, works as designed.
There is an opportunity for better communication in the app and the documentation