268 lines
7.0 KiB
Markdown
268 lines
7.0 KiB
Markdown
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# Choosing your configuration
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There are only a few configurations provided by examples. If your application needs something slightly different, here is a general configuration process.
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## What number do you want?
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First, decide which data members of `gps_fix` and `NMEAGPS` you need (see [Data Model](Data Model.md) for member descriptions). Those members **must** be enabled in `GPSfix_cfg.h`.
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Next, figure out what messages can fill out those members, because those messages **must** be enabled in `NMEAGPS_cfg.h`. Here is a table of the NMEA messages parsed by NeoGPS, and which data members they affect:
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<table>
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<tr>
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<td><p align="right"><b>Message</b></p><p><b>Data Member</b></p></td>
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<td><p>GGA</p><p><br></p></td>
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<td><p>GLL</p><p><br></p></td>
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<td><p>GSA</p><p><br></p></td>
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<td><p>GST</p><p><br></p></td>
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<td><p>GSV</p><p><br></p></td>
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<td><p>RMC</p><p><br></p></td>
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<td><p>VTG</p><p><br></p></td>
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<td><p>ZDA</p><p><br></p></td>
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<td><p align="center">PUBX<br>00<sup>1<sup></p><p><br></p></td>
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<td><p align="center">PUBX<br>04<sup>1<sup></p><p><br></p></td>
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</tr>
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<tr><td><p><b>class gps_fix</b></p></td></tr>
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<tr>
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<td><p align="right">status</p></td>
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<td>*</td>
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<td>*</td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">date<sup>2</sup></p></td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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</tr>
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<tr>
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<td><p align="right">time<sup>2</sup></p></td>
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<td>*</td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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<td>*</td>
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<td>*</td>
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</tr>
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<tr>
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<td><p align="right">lat/lon</p></td>
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<td>*</td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">altitude</p></td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">speed</p></td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">heading</p></td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">satellites <sup>3</sup></p></td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">HDOP</p></td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">VDOP</p></td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">PDOP</p></td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">TDOP</p></td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">Velocity North,<br>
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East,<br>
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Down</p></td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>* <sup>4</sup><br>* <sup>4</sup><br>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">lat, lon, alt error</p></td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">speed error,<br>
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heading error,<br>
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time error <sup>5</sup></p></td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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</tr>
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<tr><td><p><b>class NMEAGPS</b></p></td></tr>
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<td><p align="right">satellite IDs <sup>3</sup></p></td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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</tr>
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<tr>
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<td><p align="right">satellite azimuth,<br> elevation and<br> signal strength <sup>3</sup></p></td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td>*</td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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<td> </td>
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</tr>
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</table>
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This table illustrates the poor design of the NMEA message set: it requires multiple messages to deliver a complete fix (i.e., all members of `gps_fix`). This also explains why many manufacturers provide proprietary messages that *are* more complete. Above, you can see that the `$PUBX,00`<sup>1</sup> message contains all members except `date`.
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While the manufacturer's specification will document all sentences supported for your device, you can also find general descriptions of many NMEA sentences [here](http://www.gpsinformation.org/dale/nmea.htm), [here](http://aprs.gids.nl/nmea/) or [here](http://www.catb.org/gpsd/NMEA.txt).
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<hr>
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<sub><sup>1</sup> The NMEA proprietary messages "PUBX" are only availble in the `ubloxNMEA` class. See [ublox-specific instructions](ublox.md) for adding this class to your configuration.</sub>
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<sub><sup>2</sup> Date and time are both stored in one member of `gps_fix`, called `dateTime`. The `fix.dateTime` member is a C++ class that has both date-oriented members (Date, Month and Year) and time-oriented members (Hours, Minutes and Seconds). See [NeoTime.h](/src/NeoTime.h) for the complete description and capabilities of the `dateTime` member, such as date/time arithmetic and conversion to/from seconds since the epoch. Hundredths of a second are stored in a separate member of `gps_fix`, called `dateTime_cs`, and can also be accessed with the functions `dateTime_ms()` and `dateTime_us()`.</sub>
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<sub><sup>3</sup> The `fix.satellites` member identifies how many of these satellites were used to calculate a fix. The number of satellites' information available in the `gps.satellites[]` array is stored in `gps.sat_count`. This the total number of satellites that may or may not be used for calculating a fix.
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<sub><sup>4</sup> Only Velocity Down is provided by the PUBX,00 message. A utility routine is provided to *calculate* Velocity North and East from Speed and Heading, if enabled. See `calculateNorthAndEastVelocityFromSpeedAndHeading` in gps_fix.h.
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<sub><sup>5</sup> These fields are only available from UBX binary messages.
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