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manora
Occasional Visitor
Joined: Mar 11, 2005
Posts: 34
Location: North West Wales
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 Posted: Wed Feb 04, 2009 10:49 am Post subject: Compass, how accurate? |
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I have been trying to set the electronic compass.
I have followed the instructions in the Satmap, rotate though 720 deg, hold level etc but it seems to register about minus 15 degs when compared to a normal magnetic compass in the same location at the same time.
I've had a look at the manual setting and the declination showing is as correct as is possible without fractions for this location.
I know the electronic compass is nice to have but not essential, but I hate things which don't work as they should, and I certainly wouldn't rely on it.
Anybody else notice a problem or is it just me? |
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M8TJT
The Other Tired Old Man
Joined: Apr 04, 2006
Posts: 10118
Location: Bexhill, South Sussex, UK
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| Posted: Wed Feb 04, 2009 11:12 am Post subject: |
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Could it be that satmap is using a true N reference but a magnetic compass ref is mag north. This means with a W mag dev, the TN based system will under-read the MN device by the MagVar. But this does not account for all of the 15 deg error that you have. Presumably you have no ferrous objects near the mag compas causing mag deviation. 
Edit Or am I talking a load of poo  |
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manora
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Joined: Mar 11, 2005
Posts: 34
Location: North West Wales
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| Posted: Wed Feb 04, 2009 11:58 am Post subject: |
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The Satmap is using magnetic north, as does the "real" compass of course. The Satmap and the compass are side by side so any outside influence should effect both equally.
I've played about some more using a paper map and have come to the conclusion that if I need to be accurate then I will use a real compass.
One point is that what ever setting I use for "Display" ie grid or magnetic I don't see a difference in the actual heading displayed or in the direction the compass points.
I think I'll stop now as I will end up going round in circle with or without a map and compass.  |
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Dave_the_Hiker
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Joined: Dec 13, 2008
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| Posted: Wed Feb 04, 2009 1:59 pm Post subject: |
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If you are getting the electronic compass to give a reading which is "only" 15 degrees out I think you are doing rather well. I have never managed to better this on any electronic compass. The Garmin units (and I have the Vista HCx and have had the GPSMAP 76CSx and Oregon) certainly don't do any better with any regularity and that is immediately after calibrating. In my opinion the electronic compass is only useful for approximately orientating the map on the Satmap while stationary.
Page 15 of the Active 10 manual says:- "An electronic compass does not give as accurate a bearing as a standard silver point magnetic compass."
Dave
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SatMap Active 10 - 1:50K maps
Garmin Vista HCx - Topo GB II, City Navigator Europe.
HTC Artemis - Memory Map, Tomtom 6
TomTom 520 - 8.320 firmware 815 maps. |
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manora
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Joined: Mar 11, 2005
Posts: 34
Location: North West Wales
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| Posted: Wed Feb 04, 2009 2:40 pm Post subject: |
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Fair point Dave, I don't have any prior experience of electronic compasses but I wouldn't want to walk too far on a heading that was 15 deg out.
I will continue to pack my trusty Silva and paper map when out and about.
Thanks for the advice.
Peter |
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mikealder
Pocket GPS Moderator
Joined: Jan 14, 2005
Posts: 19638
Location: Blackpool , Lancs
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| Posted: Wed Feb 04, 2009 2:50 pm Post subject: |
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But with your position and trail displayed on the map you can easily see where you have been and where you are going, even in total fog where an electronic compass is useless if you cannot see reference points to triangulate from - I seldom use the built in compass as I don't find its use of any value whilst walking.
If I were using it on a boat then I guess it could be handy, aircraft contain their own instruments which I would use rather than a handheld device - Mike |
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philpugh
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Joined: Dec 28, 2005
Posts: 2003
Location: Antrobus, Cheshire
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| Posted: Wed Feb 04, 2009 4:48 pm Post subject: |
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The other point is that an electronic compass will affect the battery life of the device.
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Phil |
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Dave_the_Hiker
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Joined: Dec 13, 2008
Posts: 48
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| Posted: Wed Feb 04, 2009 5:21 pm Post subject: |
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| manora wrote: | Fair point Dave, I don't have any prior experience of electronic compasses but I wouldn't want to walk too far on a heading that was 15 deg out.
I will continue to pack my trusty Silva and paper map when out and about.
Thanks for the advice.
Peter |
What you need to do is to go to "settings" then "units and set speed" then change "Target Speed" to "1 kph".
This ensures that as soon as you start walking the "Compass" derives its data from the satellites not the electronic compass. You will then find that the heading is very accurate.
The electronic compass is next to useless and as Mike says. You can see where you are on the map so you shouldn't get lost.
It's just a pity that you can't turn the electronic compass off all together, as you can with Garmin units, to save power.
_________________
SatMap Active 10 - 1:50K maps
Garmin Vista HCx - Topo GB II, City Navigator Europe.
HTC Artemis - Memory Map, Tomtom 6
TomTom 520 - 8.320 firmware 815 maps. |
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manora
Occasional Visitor
Joined: Mar 11, 2005
Posts: 34
Location: North West Wales
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| Posted: Wed Feb 04, 2009 5:43 pm Post subject: |
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| Dave_the_Hiker wrote: |
What you need to do is to go to "settings" then "units and set speed" then change "Target Speed" to "1 kph".
This ensures that as soon as you start walking the "Compass" derives its data from the satellites not the electronic compass. You will then find that the heading is very accurate.
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Good idea, I will do that. One point, the setting is under "GPS Settings" then "GPS Used as Heading at"
The one you quoted is used to calculate ETA etc.
Peter |
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Dave_the_Hiker
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| Posted: Wed Feb 04, 2009 7:17 pm Post subject: |
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You are right of course. While on that page I have found it worthwhile to change "Altitude from GPS" to "Altitude from Maps". Altitude from GPS is notoriously inaccurate.
Dave
_________________
SatMap Active 10 - 1:50K maps
Garmin Vista HCx - Topo GB II, City Navigator Europe.
HTC Artemis - Memory Map, Tomtom 6
TomTom 520 - 8.320 firmware 815 maps. |
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4ndynorfolk
Regular Visitor
Joined: Jul 02, 2008
Posts: 237
Location: Norfolk
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| Posted: Wed Feb 04, 2009 7:54 pm Post subject: |
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Philpugh wrote: | Quote: | | The other point is that an electronic compass will affect the battery life of the device. |
I seem to recall that when I first got my Satmap last June with version 1.16 there was somthing in the manual about de-activating the compass to save power. I can't find it now. Was it simply by never calibrating it from new/ factory reset?
Does anyone else remember this? |
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GB5
Occasional Visitor
Joined: Feb 04, 2009
Posts: 2
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| Posted: Wed Feb 04, 2009 8:46 pm Post subject: Satmap Electronic compass |
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I asked Satmap about the accuracy of the electronic compass earlier this week they said it can be about 15 degrees out and recommend the use of a normal compass and map in hazardous conditions.
As a newcomer to the site I would like to thankyou all for the positive / negative comments and excellent review about the Satmap unit. I purchased one a couple of weeks ago after the latest version was issued and its much better than the one I tried a year ago.
Time to obtain a cold GPS lock is around three minutes. |
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philpugh
Lifetime Member
Joined: Dec 28, 2005
Posts: 2003
Location: Antrobus, Cheshire
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| Posted: Thu Feb 05, 2009 6:17 pm Post subject: |
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| Dave_the_Hiker wrote: |
What you need to do is to go to "settings" then "units and set speed" then change "Target Speed" to "1 kph".
This ensures that as soon as you start walking the "Compass" derives its data from the satellites not the electronic compass. You will then find that the heading is very accurate. |
As I am thinking about the possibility buying the Active10 (rather than spend quite a bit of money on the GB Explorer maps for my Colorado 300). Do you get a 'direction vector' displayed when moving. I mean something like the pointer you get on Anquet on a PDA - which is doing what you describe above. It's quite a nice feature and can be very useful in unfamiliar territory.
| Dave_the_Hiker wrote: |
It's just a pity that you can't turn the electronic compass off all together, as you can with Garmin units, to save power. |
Hmmm.... hope this is something they are going to change - never use the one on my C300 - always use my trust Silva. But you can turn the C300 compass off as you say.
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Phil |
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mikealder
Pocket GPS Moderator
Joined: Jan 14, 2005
Posts: 19638
Location: Blackpool , Lancs
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| Posted: Thu Feb 05, 2009 6:23 pm Post subject: |
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| philpugh wrote: | | Do you get a 'direction vector' displayed when moving. I mean something like the pointer you get on Anquet on a PDA - which is doing what you describe above. It's quite a nice feature and can be very useful in unfamiliar territory. |
Yes, this feature has been recently introduced with the latest software upgrade.
As for turning off the compass I don't see as it will be much of a battery drain, with the LiPol battery fitted it is easy to get over one days worth of walking using the device - There is the other option for high power rechargable AA cells, a couple of sets would get you through a weekend - Mike |
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4ndynorfolk
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Joined: Jul 02, 2008
Posts: 237
Location: Norfolk
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| Posted: Thu Feb 05, 2009 7:58 pm Post subject: |
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| Quote: | | There is the other option for high power rechargable AA cells, a couple of sets would get you through a weekend - Mike |
I wouldn't use high power rechargables in this way. I have found that the so called "hybrid" or "ready to go" rechargables are much better dispite only being 2100mAh compared with a high power 2800mAh cell.
The reason being the self discharge rate on standard nimh batteries which is often quoted as being 20-25% in the first 24 hours then 10-15% per month. The "hybrid" cells are claimed to hold 80% charge after 12 months.
So, unless you can use these high power cells straight from the charger, that extra capacity is lost within a day.
I have these in My Fuji 9600 bridge camera. It can sit in the cupboard for months, but always has loads of power when I come to use it.
Google "Uniross HYBRIO" to find the best deals. |
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