GPXIN-28: E_WARNING raised if Speed not present (but calculated)

I need to double check, but my guess is we're probably not generating the acceleration stats if speed isn't present in the source. GPXIN-13 implemented calculating time moving when calcDistance is used, but I don't think we've touched Accel/Deccel stats yet.

GPXIN-16 also saw these errors, the fix at the time was to suppress speed if it wasn't present in the GPX file, but the implementation of calcDistance (GPXIN-6) has essentially overridden that protection.

We calculate accel stats here - https://github.com/bentasker/PHP-GPX-Ingest/blob/5414ad85e032348864f6c13fbe5867a935f57516/GPXIngest.class.php#L490

list($acc,$decc) = $this->calculateAcceleration($ptspeed,$time,$unit);

But ptspeed is supposed to be set during the calculations

						// Added for GPXIN-13
						if (!$trkpt->desc || empty($speed_string)){
						      // Calculate the speed based on distance travelled and time
						      // distance is in feet

						      // Avoid div by 0
						      if ($this->entryperiod == 0){
							    $speed_string = "0 MPH";
							    $ptspeed = 0;
						      }else{						    
							    $fps = $dist / $this->entryperiod; // Feet per second
							    $mph = round(($fps * 0.681818),0);
							    $speed_string = "$mph MPH";
							    $ptspeed = (int)$mph;
						      }
						      // Make sure the metadata shows we did this calculation
						      $this->journey->metadata->AutoCalc['speed'] = true;
						}

Dropping some debug into calculateAcceleration we do seem to be passing it calculated values

Called with 14, 1247348337, mph
Called with 15, 1247348352, mph

And we do seem to be getting Acceleration stats

[maxacceleration] => 0.0298
[maxdeceleration] => 0.2235
[minacceleration] => 0.0298
[mindeceleration] => 0.2235
[avgacceleration] => 0.03
[avgdeceleration] => 0.22

So it doesn't look like that's the root cause.

Will try and get a copy of the GPX file the user is using - wonder if they've got a track with only one trackpoint or something? Should really check whether those arrays are empty before running max/min on them though

The user has provided an example GPX:

<?xml version="1.0" encoding="UTF-8"?>
<gpx version="1.1" creator="GPS Track Editor" xmlns="http://www.topografix.com/GPX/1/1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:gte="http://www.gpstrackeditor.com/xmlschemas/General/1" xmlns:gpxtpx="http://www.garmin.com/xmlschemas/TrackPointExtension/v1" xmlns:gpxx="http://www.garmin.com/xmlschemas/GpxExtensions/v3" targetNamespace="http://www.topografix.com/GPX/1/1" elementFormDefault="qualified" xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd">
<metadata>
	<name>GPS_2010-04-08_070150</name>
</metadata>
<trk>
	<name>ACTIVE LOG</name>
	<trkseg>
		<trkpt lat="32.069516" lon="34.786010">
			<ele>23.17</ele>
			<time>2010-04-08T07:01:50Z</time>
		</trkpt>
		<trkpt lat="32.069516" lon="34.786010">
			<ele>25.23</ele>
			<time>2010-04-08T07:01:51Z</time>
		</trkpt>
		<trkpt lat="32.069516" lon="34.786010">
			<ele>26.37</ele>
			<time>2010-04-08T07:01:55Z</time>
		</trkpt>
		<trkpt lat="32.069516" lon="34.786010">
			<ele>19.80</ele>
			<time>2010-04-08T07:01:59Z</time>
		</trkpt>
		<trkpt lat="32.069516" lon="34.786010">
			<ele>26.00</ele>
			<time>2010-04-08T07:02:00Z</time>
		</trkpt>
		<extensions>
			<gte:name>#6</gte:name>
			<gte:color>#00ffff</gte:color>
		</extensions>
	</trkseg>
</trk>
</gpx>

The speed (and by extension (ac|de)cel) calculations are based on lat/lon. But in that file they're static (though the user's elevation is changing) so we wouldn't record any values to push into those arrays.

Which by extension, means that if, over a number of trackpoints, a user doesn't change speed at all (however unlikely that might be) we won't be generating stats for that either, which would have an effect on the averages generated.

Whether or not that's a bad thing I can't decide. If we introduce calculation of 0 values then we're talking average acceleration over a track. Without, we're talking average rate of acceleration when accelerating which is a subtle but fairly important distinction. I can see a use-case for both, though I think the currently existing stats will have to continue to use the status quo, as the calculations are correct (if a little ambiguous) I don't want to break b/c over them

I think this is as fixed as it can ever be.

Having a file with absolutely no lat/lon present, but static, whilst only elevation changes across the whole file is such an edge case (unless you're interested in tracking journeys in lifts), that it doesn't seem worth putting too much effort into.

The commit above should have fixed the warnings in any case.