While NMEA charges a hefty fee (hundreds of dollars) for the document, summaries are available for the price of a little web search fu. (There were a few surprises here and there.)Īll of these devices emit ASCII data in a standard format described in the document NMEA 0183 Standard for Interfacing Marine Electronic Devices (version 4.10, NMEA 0183, National Marine Electronics Association, 2012-06). My tiny little company ended up buying a large assortment of these devices - ten in all, plus a few other more special purpose GPS devices that didn't have USB interfaces - allowing me to test Hazer against a broad range of of NMEA sentences. This turned out to be really useful when I was working on Hazer, a simple little C library to parse NMEA GPS sentences. Most are pretty inexpensive: a few tens of dollars, if that. But GPS-over-USB devices are really useful for quickly cobbling together a geolocation application like I described in Better Never Than Late, or for determining the general time-of-day at least to the nearest second.Ī quick search for "GPS USB" on reveals a pile of such devices (and lots of other stuff). Such devices are not appropriate for the the kinds of precision timing applications I described in Engines of Time my attempt to do so quickly revealed the latency and jitter that the serial-to-USB conversion introduces, and that is deadly to Network Time Protocol (NTP) applications. All of these devices have been used with my own GNSS software. In this article I briefly describe these devices, what I've used them for, and give you some useful information about each. Some have an actual RS232 serial port, or logic level serial output. For most of these devices, the NMEA output is funneled through a Universal Serial Bus (USB) interface. I've had several occasions to make use of Global Navigation Satellite System (GNSS) receivers that emit National Marine Equipment Association (NMEA) serial output.
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