N900 Hardware GPS


[edit] Hardware

The GPS in the N900 is a TI GPS5030 - navilink 5. [1]

The Navilink series is detailed here.

The GPS is not connected to the main CPU, but to the processor in the phone module, hence cannot be communicated with directly. [2]

It is connected through I2C, and a 4 bit data connection, see Page 10 of the schematic.

The GPS uses approximately 50 mA when enabled, and logging once per second using location test GUI. See also N900 Hardware Power Consumption

[edit] Software

The GPS is driven through the liblocation library, which supports several modes of location, some of which use the GPS, some use external data to improve lock times, and some that do not use the GPS at all.

There are many user applications that use the GPS, from simple loggers, like GPS data logger to openstreetmap editors and even commercial replacements for the free Ovi maps software.

[edit] Phonet Protocol

See N900_GPS_Reverse_Engineering

[edit] Accuracy

Over a long period in one position with a clear view of the sky, the horizontal accuracy is outlined in this graph.

  • 50% of points within 2.4m
  • 90% within 4.2m
  • 99% within 18m
  • 99.9% within 80m.

Percentage points falling within the given radius in decimeters (1/10th of a meter)

The outliers are explored in detail here.



[edit] Bugs

A number of users have reported poor or no lock in circumstances where the phone should obtain a GPS lock. See this (now closed) bug for more information and if you are still affected by this. (read all of the bug carefully)