Several reasons can induce a gap between the location provided by the Atlas service and the actual device location.
Sigfox messages can be received by base stations quite far from the device. Some messages actually reached a distance greater than 1000 km. This can cause impair the device position accuracy.
Moving devices cause location calculation performances to be significantly degraded.
Low RSSI and a low number of receiving base stations can impact location computation.
Device at ocean level / coastal areas
Signal propagation over the ocean is very good, leading to base stations receiving messages far from the device. Location performance on a waterfront is significantly degraded.
Devices at altitude
When a device is located in altitude and with a clear line-of-sight, numerous base stations can receive the message, some being in line-of-sight conditions, leading to a misinterpretation of the collected data.
Base stations at altitude
These base stations will capture signals emitted by devices far from them. That will increase the average error, which is why these base stations are often excluded from location computation. These stations will only be used when no located data is available.