Sparkfun has just started selling the excellent 5Hz Locosys LS20031 GPS module that Dean Goedde is using with Attopilot. It uses the Mediatek chipset, which doesn't have a binary mode, but is otherwise great at getting a lock fast and keeping it. Cost is $59.95. Details:
# 32 Channel GPS
# Fast TTFF at low signal level
# Up to 5Hz update rate
# Capable of SBAS (WAAS, EGNOS, MSAS)
# Built-in micro battery to reserve system data for rapid satellite acquisition
# LED indicator for fix or no fix
I have considered taking Curtis Olson's approach of 10Hz interpolation of 4Hz or 5Hz GPS data to get higher resolution. A GPS Rx that already gives 10Hz would be nice and do the hard work for us already. On the other hand, what I have found in extensive AttoPilot flight testing is at 5Hz, typical flight speed of say 75 km/h (21 m/s) that only 4m elapses between GPS updates. 4m is on the order of GPS position resolution, so 10Hz and 2m is not really noticable. At say 100+ km/hr the 10Hz updates should start to make a difference.
Not necessarily. But if you don't have a lot of processor power to spare, if you're reading GPS at 5Hz in ASCII the parser can take up a lot of cycles. Binary mode is a less work for the processor. It's not a problem at 1hz, but if you're using this module with Arduino at 5Hz, you'll need to ensure that your ASCII NMEA parser is effecient (interrupt driven, etc). We've discussed how to do this and shared some code in this thread.
Comments