Advertise on DISCO3.CO.UK
Forum · Gallery · Wiki · Shop · Sponsors
  Home · FAQ · New Posts · My Posts · PMs · Search · Members · Members Map · Groups · Profile · Donate · Register · Log In  
DISCO3.CO.UK > General (D4)

Speedo Speed vs GPS Speed
Post Reply  Down to end
Page 1 of 1
MadJax
 


Member Since: 30 May 2011
Location: Adelaide
Posts: 120

Australia 2010 Discovery 4 TDV6 SE Auto Stornoway GreyDiscovery 4
Speedo Speed vs GPS Speed

Is it just me or does my speedo show a slower speed than my GPS device Question

I do need to do some more testing but I believe a 10% difference is shown, the speedo being slower.

Not only that but I cannot find a Sat Nav function that shows speed. Which is interesting.


What are your views on this


Thanks Thumbs Up Discovery 4 2.7 SE
Defender 130 TD5 - Daily Drive
2.7t Caravan
Java TD5 HSE - Gone but not forgotten.
Java V6 Freelander - Had fun in it.  
Post #80702315th Jun 2011 12:15 pm
View user's profile Send private message View poster's gallery Reply with quote
Voug
 


Member Since: 03 Dec 2010
Location: Somewhere between East and West
Posts: 195

Germany 2011 Discovery 4 3.0 TDV6 HSE Auto Baltic BlueDiscovery 4

Checked yesterday my blackvue recordings ... 120 km/h at the cruise control / speedo gives 117 km/h via GPS. Thats okay.  
Post #80703615th Jun 2011 12:33 pm
View user's profile Send private message View poster's gallery Reply with quote
DG
Site Moderator 


Member Since: 12 Dec 2005
Location: The Gaff
Posts: 50979

Wales 

Your speedometer should never read less than your true speed .......but it is allowed to display more than your true speed by a certain percentage (well, under EU regs, not sure about AUS) 21 year LR veteran > D2 GS 2003 > D3 S 2006 > D3 HSE 2009 > D4 HSE 2013 > D4 HSE 2015 > D5 HSE 2018 > DS HSE R-Dynamic P300e 2021 

Last edited by DG on 16th Jun 2011 12:21 am. Edited 1 time in total 
Post #80704015th Jun 2011 12:45 pm
View user's profile Send private message View poster's gallery Reply with quote
RichardB
 


Member Since: 03 May 2010
Location: Hants
Posts: 485

United Kingdom 2010 Discovery 4 3.0 TDV6 XS Auto Nara BronzeDiscovery 4

I've been using GPS units in cars for 20 years odd. Before all 24 satellites were in place and well before Selective Availability was switched off officially by Bill Clinton and tomtom was running on a psion 3.

Never yet had a car where the GPS registers lower than the speedo. As DG says, speedos must not under report speed for obvious reason. So they are pretty universally calibrated to overreport. Usually around 5% to a max of 10%. My D4 seems to pretty reliably do 70 GPS (true) when the clock gives 70 and 50 is 53/54. mph that is. Useful to know for the UKs average speed check cameras.

Clearly, the speedo does not take a feed from the in car GPS! I also suspect it's why built in units don't show speed on the Nav display from the GPS.

May be obvious but GPS units derive speed indirectly from 2 position readings, usually about 1 second apart or so. They may also overlay this with a moving average to provide damping. Consequently GPS speeds lag true speed,
so make comparisons when running at a steady speed!

As a result, if your speedo is under reading consider getting it checked especially if under warranty.  
Post #80724615th Jun 2011 8:38 pm
View user's profile Send private message View poster's gallery Reply with quote
kenny
 


Member Since: 17 Jan 2010
Location: South West Aus
Posts: 79

Australia 2011 Discovery 4 3.0 TDV6 SE Auto Siberian SilverDiscovery 4

From memory the speedo is set to +3% +3kph here in Aust on the CCF. If you have the touch screen and set it to diagnostic mode there is a screen in there that will show the GPS speed and the MOST Buss speed. Those two speeds are almost identical to each other, it's only the dashboard display that is higher.  
Post #80731015th Jun 2011 10:36 pm
View user's profile Send private message View poster's gallery Reply with quote
MadJax
 


Member Since: 30 May 2011
Location: Adelaide
Posts: 120

Australia 2010 Discovery 4 TDV6 SE Auto Stornoway GreyDiscovery 4

I should have looked at the diagnostic screen earlier.

Will try it over the weekend Thumbs Up Discovery 4 2.7 SE
Defender 130 TD5 - Daily Drive
2.7t Caravan
Java TD5 HSE - Gone but not forgotten.
Java V6 Freelander - Had fun in it.  
Post #80731815th Jun 2011 11:36 pm
View user's profile Send private message View poster's gallery Reply with quote
hughes_jh
 


Member Since: 09 Jan 2011
Location: Warwickshire
Posts: 294

United Kingdom 2006 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

Speedo needs to show a tad higher than actual to allow for any uncontrollable variation, even things like tyre wear will affect the speedo (the theory being that your car goes faster on new tyres due to the larger diameter)  
Post #80736016th Jun 2011 8:04 am
View user's profile Send private message View poster's gallery Post Reply
Display posts from the last:  
Post Reply Back to top
Page 1 of 1
Jump to:  
< Previous Topic | Next Topic >


Posting Rules
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum



DISCO3.CO.UK Copyright © 2004-2024 Futuranet Ltd & Martin Lewis
DISCO3.CO.UK RSS Feed - All Forums
DISCO3.CO.UK is independent and not affiliated to Land Rover.
Switch to Mobile Site