Unsurv Technologies
Security & Privacy

unsurv offline

An open source, privacy friendly, compact GNSS receiver with ESP32 and NFC for all your location based projects, including tracking surveillance cameras

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unsurv offline is a privacy friendly, small and lightweight PCB (45 mm x 32 mm) based on an ESP32 featuring a high quality GNSS receiver, accelerometer, and NFC capabilities. Using a combination of onboard features and OpenStreetMap (OSM) data, unsurv offline helps you collect and analyze location data in a privacy-friendly way. Originally conceived to better understand offline video surveillance, this fully open source project is here to help you find and develop a variety of custom use cases.

To visualize the expanding video surveillance network, this device can generate a daily report of your close encounters with surveillance cameras without exposing your location to any 3rd party. It does this by using a database of camera locations from the OSM on the SD card. Please watch our demo above for more information about this use case.

You can access your unsurv data easily using your smartphone (or any NFC Tag 4 capable reader) and the dynamic NFC tag integrated into the case. A tiny BMA400 accelerometer helps you save precious battery capacity by managing power-saving features. It can even be adapted as an input device with tap and double tap recognition or as a fitness tracker with step counter and running/walking detection.

The kit option includes a high quality 3D printed case with enough space to house a 300 mAh single cell LiPo battery, which can be charged via onboard USB. Do you have access to a 3D printer? Great! The case design files are open source, so you can choose the PCB + antenna version and print the case yourself.

Track the data that is tracking you.

unsurv offline is built to help track a variety of data points. You can track the surveillance cameras that have potentially seen you throughout your day. It will also do simple location logging, automated commute tracking, and map WiFi signal strength. This means you could log your daily commute by bike and ensure that nobody except you has the data. You could map WiFi signal strength in your city and create a map of free WiFi access points. If you use vehicles commercially and want to claim tax benefits, you could use unsurv offline to log each trip. Since unsurv offline is open source, you can utilize the source code to come up with your own custom uses.

Here is a short list of the provided use cases you can build upon:

All of these will work with the unsurv companion Android app that you’ve seen in the demo and will be added to an Arduino IDE library for ease of use later on. They can also be found on the unsurv GitHub repository.

Why Not Use Location Tracking On Your Phone?

Implementing an always-on location service on a smartphone is possible, but comes with certain drawbacks: it increases power draw and might not be sustainable throughout the day. Even worse, it potentially exposes your location to third parties, taking away from the privacy focus. unsurv offline solves for all of this as a customizable lightweight, portable, low-power board with every feature you need for powerful location tracking.

Features & Specifications


unsurv-offlinecricketTrackiAbeeway MicroTTGO T-Beam
Size (mm) 45 x 32 46 x 23 46 x 38 59 x 34 100 x 33
Host ESP32 STM32L082 Unknown Unknown ESP32
Main access NFC / SD card / App LoRaWAN App / Web Web LoRaWAN / Display
WiFiYes No Yes Yes Yes
BluetoothYes No No No Yes
Motion sensingYes Yes Yes Yes No
Open sourceHW + SW HW only No No HW + SW
Requires subscriptionNo No $20 / month No (for personal use) No

Support & Documentation

All files for unsurv offline are open source and editable with free tools. The PCB has been desinged using KiCad while the case is designed using FreeCAD You can follow development and have a look at the hardware design and software on our GitHub repository. You can also find the codebase for the Android companion app to interact with your device.

Interested in This Project?

Please reach out with any questions using the Ask a technical question page, listed in the link below.

In the Press

Geeky Gadgets

"...the open source unsurv offline board offer[s] users a privacy friendly, small, lightweight PCB loaded with an ESP32, GNSS receiver and featuring NFC."


"Unsurv,... is an offline privacy-friendly, small, lightweight PCB (43 mm x 32 mm) loaded with an ESP32, GNSS reciever and NFC capabilities."


"This week saw a rad retro Raspberry Pi Zero camera, 3D models on an ESP32, CircuitPython Day, and more maker madness! "

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Produced by Unsurv Technologies in Stuttgart, Germany.

Sold and shipped by Crowd Supply.

unsurv offline PCB + case + antenna

Full kit including the PCB, case, and external NFC antenna

$99 $8 US Shipping / $18 Worldwide

About the Team

Unsurv Technologies

Stuttgart, Germany  ·   unsurv.org

Creating tools to better monitor offline surveillance.

Martin Wieland

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