Speed indication in SmartST V2

uffe73 · Posted: Mon Nov 01, 2004 11:26 pm Post subject: Speed indication in SmartST V2

Hi all,

I wasn't sure if I should post this question in the SW or HW section as the answer is probably depending on both...

Anyway, I'm wondering why my Navman 4410 GPS with SmartST V2 won't give me a better speed accuracy than 3-4 km/h. According to a GPS site on the internet it should be possible to achieve a speed accuracy of 0.2 m/s with a clear sky which is equal to 0.72 km/h. This is for most GPS systems achieved by means of Kalman filtering.

The funny thing is that I tend to get only certain speed indications displayed in SmartST, but never those inbetween. As an example I can get the following speed indications: 100 km/h, 104 km/h, 108 km/h, 111 km/h, 115 km/h, 118 km/h, 122 km/h, 126 km/h but never those inbetween. I have tested this with the cruise control of my car. I have to press the "accelerator button" on my cruise control four times to get SmartST to change from 118 km/h to 122 km/h, which should indicate that the speed increment of the cruise control is about 1 km/h per button push.

There is probably a logic explanation to this behaviour and I'm very curious to hear it. Are there any big differences between different GPS systems when it comes to calculating speed? Can I expect any improvement in SmartST V3 regarding this?

Finaly, does anyone know if it's really possible to achieve a speed accuracy of 1 km/h? If that is possible, I could use my GPS System as a more realiable speedometer than the one built into the car, since the speed displayed by the car speedomeeter is always about 10km/h too high.

A lot of questions...

/Ulf

lbendlin · Posted: Mon Nov 01, 2004 11:38 pm Post subject:

This is clearly a software bug. Some programmer made a rounding error with the conversion.

Interestingly enough Smart ST is not the only software with that problem. Mapopolis also shows only select speeds in its log file, similiar to the values you list. And it refuses to accept speeds above 156 mph (think plane taking off).

You should report your findings to Navman and ask them to fix it.
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uffe73 · Posted: Fri Nov 05, 2004 1:06 pm Post subject:

Just wanted to mention that the bug/problem has been forwarded to the testers at Navman.

It would be interesting to know if the problem can be reproduced in SmartST V3. Is there anyone out there who owns an iCN 510 or pIN 300 and who could test this and let me know?

How good is the resolution of the speed indication when mph is selected as speed unit? Can you get all mph speed values displayed in SmartST?

/Ulf

uffe73 · Posted: Mon Nov 29, 2004 11:25 am Post subject:

Hi again,

Could anyone with a SmartST V3 device let me know if Navman have fixed the problem with displaying of speed? If the correct algoritm for speed calculation is used, the accuracy should be better than 1 km/h. The resolution in SmartST V2 is 3-4 km/h.

Regards,

Ulf

Tim Buxton · Posted: Mon Nov 29, 2004 12:07 pm Post subject:

I tried this a short while ago, but then forgot about it. When I'm in Navigate mode and I have speed displayed, it is as you describe. I tried at places on the M25 where it is straight and flat, using cruise control and I could only get certain speeds displayed. (I'd set my unit to display kph.) On the return journey I used the GPS status screen to observe my speed and this appeared to display 'proper' speed. It certainly showed speeds which weren't shown in on the Navigate screen.

I wonder if Navman have put in some sort of filter to smooth out the speed readout on the Navigate screen, something like "If the speed is between 115 and 115kph, show 118" for instance.
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uffe73 · Posted: Mon Nov 29, 2004 12:52 pm Post subject:

Aha, that's interesting. I've never tried to use the GPS status screen for this. Too bad that there's no quick way (without using the stylus) to switch between the navigation screen and the GPS Status screen.

So this sound like the implementation of speed indication in V3 is similar to V2. I haven't got any response from Navman saing if they intend to fix this or if the current behaviour is according to their specs.

Anyway, thanks for the information, Tim!

/Ulf

UKHABU · Posted: Mon Nov 29, 2004 1:27 pm Post subject:

There is a quick(er) way! click the joystick once left and you can then just tap with a finger the GPS Status screen.
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icsys · Posted: Wed Dec 01, 2004 2:48 pm Post subject:

Tim Buxton · Posted: Wed Dec 01, 2004 2:53 pm Post subject:

OK then, one press of the left hand rocker, then two finger taps, the first to select the second screen and then another to tap GPS Status. :D
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uffe73 · Posted: Wed Dec 01, 2004 5:08 pm Post subject:

Well, it's not handiest way to show the speed, but it seems to be the best we have at the moment. Too bad that the voice instructions are switched off by SmartST V2 when I leave the navigation mode. I'm wondering if this is done intentionally or if it's a bug. Is it the same in V3?

I've emailed Navman twice (sent to different people) about the error in displaying speed (in navigation mode) but I still haven't got any response. It seems to me that this problem should be quite easy to fix, since the correct speed is available in the GPS status mode.

AlfieB · Posted: Wed Dec 01, 2004 5:31 pm Post subject:

Hi there

Because I use an iCN630 I'm not sure how your units function, and if I've missed the point on this thread my apologies, but I've found it most interesting.

Does this Speed display query only occur when using PDA's etc Question

When in navigation mode I tend to leave the speed display showing for the majority of the time. The unit though being set to MPH not Kph and I find it does show a full speed range, ie: 39, 40, 41, etc.

I have tried checking the reading against the speedo in my Renault and I find that as one would expect there is a consistent variation between the car and GPS. The car speed always gives a read higher than the GPS, again eg: when my speedo shows 40 mph, Navman is showing 37 mph.

regards

alfieB Thumbs Up

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uffe73 · Posted: Wed Dec 01, 2004 10:52 pm Post subject:

I've only been using the PDA (PPC) version of SmartST V2 with kph as unit, but according to Tim Buxton the same phenomenon is showing on an iCN 510. The thing to note is that the resolution of the speed indication is lower on the navigation screens than on the GPS Status screen.

icsys · Posted: Thu Dec 02, 2004 12:58 am Post subject:

If you want voice guidance and see a larger speed display try the Next Instruction screen.

You also get the Active POI alerts (both visual and sound) coming through as well.
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Tim Buxton · Posted: Thu Dec 02, 2004 4:22 am Post subject:

uffe73 · Posted: Thu Dec 02, 2004 8:27 am Post subject:

With navigation mode I meant one of the three navigation screens - north-up, 3D and the safety screen. The speed can be displayed in either the 3D view or the safety view (I don't see the reason for not displaying the same information in the north-up view as well...)

I certainly agree that the voice instructions should be active as long as a route is set and not only while displaying the map, so I guess this is a bug in the V2 SW. Maybe it's been corrected in V3.
However, I don't see a big reason to go to the GPS Status screen while driving, if the speed was only displayed correctly in the map views...

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