HappyMartin Posted July 21, 2014 Share You are better off with smart recording in most cases. It isn't based on time or distance and places points more frequently depending on how fast you are moving and and often you change direction, I'm not sure about your Garmin but all the units I have owned have had an option for smart recording. It's always worked best for me Link to comment Share on other sites More sharing options...
L'Bie Posted July 22, 2014 Share My experience with Garmin is that the vertical accent calculation becomes particularly dodgy in bad weather. When I bought my Edge500 a couple of years ago, it advertised its ability to measure elevation using better than aircraft barometric sensors. I often go out for long rides often resulting in barometric changes in the area from where I departed. Elevation at start and at end of exercise at the exact point never agreed. I did some research and wrote a letter to Garmin asking why triangulation is rejected as a means to calculate the elevation. The typical error shouldn't be more than the 10 meters that the devise promise and since the errors I encountered were often much larger than the 10 meters, it seems like the more accurate method. Remember GPS needs only 3 satellites to determine a position, but if you check your device you will find 11 or 12 at any time within range. The more satellites it sees, the more accurate the positioning should be. 12 is plenty. Garmin came back with an answer about the atmosphere, clouds etc. can stuff the triangulation up!? Really! In the most horrible weather my position recorded even shows what side of the road I was using! And if the error is less than the 10 meters accuracy, It would at least still put me above sea level when I am cycling in the mountains of Madagascar. In short, Remember that GPS we know is run by the American Air-force. They allow us to use GPS, but with a forced error so that the evil baddies can not use their own technology against them. And before you start flaming the Americans, the Russians also has a system and they follow exactly the same protocols. In the East there are developments, but they do not have enough satellites up and running yet. RockCoach 1 Link to comment Share on other sites More sharing options...
fandacious Posted July 22, 2014 Share I did some research and wrote a letter to Garmin asking why triangulation is rejected as a means to calculate the elevation that makes no sense at all. Triangulation can be used for location, not elevation. If your barometer is incorrectly initialized, then your entire ride will be wrong. Read up on resetting the garmin barometer from time to time Link to comment Share on other sites More sharing options...
Falco Posted July 22, 2014 Share Reading all this makes me so glad I'm not a techno geek, to be honest I don't understand most of it and don't really want to. My Garmin tells me what I need to know, I couldn't care less if it's out by 10 metres, or 100 metres for that matter. I just go ride and enjoy myself, even if the trip is a km longer or shorter than NASA would calculate. TopFuel, Jigghead, Jakkals. and 1 other 4 Link to comment Share on other sites More sharing options...
Brian Fantana Posted July 22, 2014 Share that makes no sense at all. Triangulation can be used for location, not elevation. If your barometer is incorrectly initialized, then your entire ride will be wrong. Read up on resetting the garmin barometer from time to time If your device has a basemap installed it can calculate your altitude by using your position (obtained from triangulation) and interpolation between contour lines. So it uses triangulation indirectly to obtain altitude. I agree with your advice to reset/calibrate a barometer regularly. Link to comment Share on other sites More sharing options...
fandacious Posted July 22, 2014 Share If your device has a basemap installed it can calculate your altitude by using your position (obtained from triangulation) and interpolation between contour lines. So it uses triangulation indirectly to obtain altitude. I agree with your advice to reset/calibrate a barometer regularly. sure, but using elevation off a map instead of baromoter will give you wild variances for your ride Link to comment Share on other sites More sharing options...
Pure Savage Posted July 22, 2014 Share After 5 hours by garmin is 1500% more accurate than my iphone because my iphone battery has long since died. nickcza, fandacious, L'Bie and 7 others 10 Link to comment Share on other sites More sharing options...
'Dale Posted July 22, 2014 Share Reading all this makes me so glad I'm not a techno geek, to be honest I don't understand most of it and don't really want to. My Garmin tells me what I need to know, I couldn't care less if it's out by 10 metres, or 100 metres for that matter. I just go ride and enjoy myself, even if the trip is a km longer or shorter than NASA would calculate. It's definitely subtle Enthusiastic enthusiasts Link to comment Share on other sites More sharing options...
L'Bie Posted July 22, 2014 Share that makes no sense at all. Triangulation can be used for location, not elevation. If your barometer is incorrectly initialized, then your entire ride will be wrong. Read up on resetting the garmin barometer from time to timeOf course it can. Triangulation it not only applicable to a flat surface. There are approximately 32 satellites revolving around earth forming part of the GPS network. If your device can see more than three of those satellites, you will have signals coming in from different elevations. See this as round spheres interlocking each other. When you are not in the centre of these interlocking spheres you have triangulation in the X, Y and Z axis. Its all maths and the accuracy of the GPS on the street is also maths. They can do it. They just won't allow it. Ask yourself if it was not possible, how do cruise missiles hit a target several hundred miles beyond direct control. That target does not have to be on sea level. It could be anywhere. The missile needs to know that. With regard to barometer resetting. Its totally immaterial if you go for a ride in clear weather at a certain atmospheric pressure. During your ride, the weather changes for and a storm develops. That is normally associated with a lower barometric pressure. You saw the storm and made it home at a time when the barometric measurement will be lower from what it was at your departure. Using barometric measurement will place you at an altitude higher than when you left. Recal is not going to cater for that. Link to comment Share on other sites More sharing options...
fandacious Posted July 22, 2014 Share Of course it can. Triangulation it not only applicable to a flat surface. There are approximately 32 satellites revolving around earth forming part of the GPS network. If your device can see more than three of those satellites, you will have signals coming in from different elevations. See this as round spheres interlocking each other. When you are not in the centre of these interlocking spheres you have triangulation in the X, Y and Z axis. Its all maths and the accuracy of the GPS on the street is also maths. They can do it. They just won't allow it. Ask yourself if it was not possible, how do cruise missiles hit a target several hundred miles beyond direct control. That target does not have to be on sea level. It could be anywhere. The missile needs to know that. With regard to barometer resetting. Its totally immaterial if you go for a ride in clear weather at a certain atmospheric pressure. During your ride, the weather changes for and a storm develops. That is normally associated with a lower barometric pressure. You saw the storm and made it home at a time when the barometric measurement will be lower from what it was at your departure. Using barometric measurement will place you at an altitude higher than when you left. Recal is not going to cater for that. you better let nasa know that their GPS satellites can calculate elevation... theres a reason your bike computer has a barometer in it Edited July 22, 2014 by Slowbee Link to comment Share on other sites More sharing options...
Slowbee Posted July 22, 2014 Share I am putting this on the watch list - this should be fun fandacious and Pure Savage 2 Link to comment Share on other sites More sharing options...
L'Bie Posted July 22, 2014 Share Reading all this makes me so glad I'm not a techno geek, to be honest I don't understand most of it and don't really want to. My Garmin tells me what I need to know, I couldn't care less if it's out by 10 metres, or 100 metres for that matter. I just go ride and enjoy myself, even if the trip is a km longer or shorter than NASA would calculate. I am ranting quite a bit here, but it is one of my pet topics. Sorry! I still believe his GPS device is not set correctly for the purpose of cycling. I use a simple Edge500 and mine tracks all those very same tracks he rode exactly. The Edge is a cycling specific GPS and I don't need to tell it at what point or at what frequency it needs to plot a waypoint (a route is just a bunch of waypoints strung together) and it may be his ultimate problem. Mine has recorded tracks in the bundus where it was almost impossible to see the footpath on Google earth. The only place where I found my Edge to stray from the truth was underneath overhead high voltage lines. Link to comment Share on other sites More sharing options...
L'Bie Posted July 22, 2014 Share you better let nasa know that their GPS satellites can calculate elevation... theres a reason your biek computer has a barometer in it Nasa uses GPS but the US Air-Force manages and controls it. Ask them about the accuracy of their missiles. Barometer comes from planes and pilots reset before take-off and they will adjust as necessary with information from airports in the vicinity. We don't see much of pilot operating anymore, because 9/11 changed all that, but pilots still fly the same way as before and the flight instruments allow for it. it is an acknowledgement if the factors I suggested. Link to comment Share on other sites More sharing options...
L'Bie Posted July 22, 2014 Share Many of us has flown before. Some landings are tougher than others. What makes these landings difficult, is the position of the pilot in relation to his landing gear. He needs to judge his height visually and he needs to keep one eye trained to the elevation so he can make an educated estimate on when it is time to feather the approach, making your live as a passenger as comfortable as possible. Pilots take pride in their jobs and good landings are amongst the items important for them (at least the ones I know). If the pilot has to rely on a barometric pressure sensor calibrated for zero in Durban, how is he going to get usable information on his approach to OR Tambo at a elevated 1685m. Link to comment Share on other sites More sharing options...
Skinnyone Posted July 22, 2014 Share The inaccuracy can also come from not setting the compass declination correctly as well... Link to comment Share on other sites More sharing options...
Stretch Posted July 22, 2014 Share for those interested in a bryton's view on life FlandersZA, L'Bie and Jakkals. 3 Link to comment Share on other sites More sharing options...
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