I've got myself a bit confused about the times I see when I open GPX files in Mem-Map EU. These files come from using Mobile Device > Import data from device, which is an HTC Touch Pro 2 running WM 6.1. I use its GPS facility with 'Pocket Nav OS5' to record walks. In my other programs the times of trackpoints in these GPX files is shown in GMT (= UTC). Most of the time this is the same in Mem-Map EU. But occasionally I find one which is apparently displaying local time. In the example that prompted this post it's BST, from a walk in May.

Can someone remind me of the 'rules' surrounding this please? And, is there any setting in Mem-Map EU (as there is in other programs, like GPS Utility) to change the way times are displayed?

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Terry, East Grinstead, UK

In a GPX file, since it has the ability to specify a time zone, the program should use that time zone. Otherwise, the program assumes UTC and uses the computer settings to display the proper time.

Thanks. I think I've almost grasped it, but the penny hasn't finally dropped! I'm not clear what you mean by your first sentence. What "has the ability to specify a time zone"?.

In your second sentence, do you mean Mem-Map EU assumes local time?

I don't see any setting in either Pocket Nav or Mem-Map EU about time zone.

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As an experiment I just changed the time on my Windows Mobile device from 1305 to 1405 (as if it was still summer, or I'd taken a trip across to Germany). Then started up Pocket Nav, recorded a brief track (one point), then re-cradled it to my PC. That caused the time on the device to switch back from 1410 to 1310. So presumably ActiveSync always sets the correct local time from my PC. But it won't have changed the data in the recorded MMO file. I then started Mem-Map EU and imported the data, which showed the trackpoint time as 1307. I also saved it as a GPX and loaded that in GPS Utilty and in my text editor. The time is 1307 in both of those too.

So I still haven't qiite simulated the situation which I think caused my original confusion! That was a walk in May (in the UK) which was therefore BST, 1 hour ahead of UTC. GPS Utility (and my text editor) show the time as UTC, Mem-Map shows it 1 hour later, which is actually the correct local time. But if I'd viewed this same import a month or two ago, when local time on my PC was BST, presumably Mem-Map would have reported this walk's trackpoints in UTC?

All very confusing!

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Terry, East Grinstead, UK

Richard,

We're coming up to the first year anniversary of my last question, so I'm assuming you didnt see it!

To repeat: "What "has the ability to specify a time zone"?

If I open a typical GPX file (made from recording a walk during British Summer Time) this is what I see. Where is the field for entering the time zone? Are you saying perhaps that this is an optional extra piece of dta that can be added manually?


<?xml version="1.0" encoding="ISO-8859-1"?>
<gpx version="1.1"
creator="Memory-Map 5.4.2.1089 http://www.memory-map.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://www.topografix.com/GPX/1/1"
xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd">
<trk>
<name>20111005Ardingly-Brian</name>
<type>Track</type>
<trkseg>
<trkpt lat="51.0565903823" lon="-0.0829984983"><ele>86</ele><time>2011-10-05T08:46:54Z</time></trkpt>
<trkpt lat="51.0561487993" lon="-0.0828144312"><ele>125</ele><time>2011-10-05T08:48:53Z</time></trkpt>
<trkpt lat="51.0561410348" lon="-0.0820926189"><ele>121</ele><time>2011-10-05T08:50:00Z</time></trkpt>
etc

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Terry, East Grinstead, UK

Hello? Anyone at Mem-Map still moniting these forums?

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Terry, East Grinstead, UK

The time zone is the "Z" at the end of the date-time string (Z = "Zulu time", which is UTC).

In principle an offset in hours and minutes can be used to show another zone (eg, "2011-10-05T09:46:54+01:00" or "2011-10-05T00:46:54-08:00", both of which are the same time as "2011-10-05T08:46:54Z"), but in practice the normal convention is for GPX files to use UTC and let the reading program decide how to convert that to local time for display.

However, this is just background info and doesn't really help with your more specific question about how MM behaves, though my guess would be that it would always store times as UTC.

Richard.

That is correct, Richard. Unless specified in the file, the program assumes UTC.

Thanks Richard.

So the only way to get MM to display the correct local time (with the read-out cursor, or in the OP window) would be to edit the GPX before loading it into MM. For example, for a walk in Southern California starting at 10:23 am local time I would have to change the first trackpoint
<trkpt lat="33.9766482671" lon="-116.1653207302"><ele>1309</ele><time>2011-02-23T18:23:19Z</time></trkpt>
to
<trkpt lat="33.9766482671" lon="-116.1653207302"><ele>1309</ele><time>2011-02-23T18:23:19-08:00</time></trkpt>
and so on?

Mem-Map: Why have you not added a simple feature to allow the user to adjust this automatically? Most other map-processing programs do so.

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Terry, East Grinstead, UK

Back to this long running but (for me) still inconclusive discussion.

Richard (rgphilpott): You seemed to provide the definitive answer I'd been seeking. If I understood correctly you said that I could change Mem-Map's behaviour by editing the GPX file, replacing all lines like "2011-10-05T08:46:54Z" with "2011-10-05T09:46:54+01:00".

Richard (USmmtech): You appeared to confirm that.

However, I just made that global replacement to a sample GPX file, but hovering over the track still shows the original times, not one hour later.

If it helps, here's the start of the revised GPX file:

<?xml version="1.0" encoding="ISO-8859-1"?>
<gpx version="1.1"
creator="Memory-Map 5.4.2.1089 http://www.memory-map.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://www.topografix.com/GPX/1/1"
xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd">
<trk>
<name>20110730-C2C-Day6</name>
<type>C2C ALL:C2C Actual</type>
<trkseg>
<trkpt lat="54.5554591497" lon="-2.7412378311"><ele>192</ele><time>2011-07-30T08:11:27+01:00</time></trkpt>
<trkpt lat="54.5550938288" lon="-2.7407826742"><ele>182</ele><time>2011-07-30T08:17:13+01:00</time></trkpt>
etc

Edit: I was mistaken. The current PC time factor must have confused me. I've now repeated several tests and summarise the results as follows:

GPX #1, walk in winter, start = 09:12 local time. Actual 1st trackpoint time in file = 09:12. Displayed by MM as 10:12 (incorrect). After global replacement = 09:12 (correct).

GPX #2, walk in summer, start 09:25 local time. Actual 1st trackpoint time in file = 08:25. Displayed by MM as 09:25 (correct). After global replacement = 08:25 (incorrect).

If I was doing this test late in the year (back on GMT instead of BST) then those results would be reversed.

On balance, reckon I'll stick with taking photo of a clock or my watch near the start of every walk. The combinations of walk date (winter, summer), location (UK, Europe, USA, etc) and the current PC Date/Time make it all too much of a PITA!

A wizard in MM might sort it, but I won't hold my breath.

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Terry, East Grinstead, UK