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Thread: Cadence Data?

  1. #1
    MTB Mamba
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    Cadence Data?

    I've been researching the Edge 705 a bit and saw that they have several different options, one without cadence and one with it.

    What exactly does the cadence option record?

    I'm assuming without the cadence option I can still at least track speed and avg. speed right?

    So what will I get with cadence as far as speed measurements etc, and what will I get without it?

  2. #2
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    I also have been researching the 705. From what I understand cadence shows RPM's. It helps a rider keep within a specific zone no matter what the gear. All versions of the 705 can do cadence if you have the cadence sensor, which you can purchase separately for around $39. The 705 still shows speed in MPH without the cadence sensor.

    If I have missed something others can chime in.

  3. #3
    MTB Mamba
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    Ok, so even without the cadence sensor I'm still going to get Speed, max/min, average etc from what it sounds like right?

    Looks like cadence might be a touch more than what I really want/need

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    Yes as speed info is calculated from the GPS portion of the 705.

  5. #5
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    The cadence sensor also measures revolutions of the wheel. If you calibrate your 705 for the circumference of your wheel, you get much more accurate speed and distance data. The GPS is pretty accurate, but wheel circumference is quite a bit more accurate. I've had the GPS readings be off by a mile on a 5.3 mile climb. It has been off by 2 miles on a 24 mile ride. Depending on your needs, that is either no biggie or unacceptable. It was unacceptable to me so I got the GSC10. Which quit working a few weeks ago and I'm very frustrated by it. I much prefer accurate data.

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    So if you use the GSC10 cadence sensor the 705 adds this information along with GPS speed data for a more accurate speed calculation? Or does it not use GPS speed data if the cadence sensor is used?

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    I believe it uses the speed sensor from the GSC10 instead of GPS.

    I initially hooked my GSC10 up just for cadence. The 305 kept using GPS for speed and distance. Then I added a spoke magnet and used it for all three (speed, distance, cadence).

    Now the GSC10 quit. I replaced the battery and it still ain't working. I'm very unhappy.

    My Forerunner 305 automatically switched back to GPS for speed and distance when the GSC10 quit. So the 305 didn't quit recording speed and distance, it switched back to GPS and simply isn't as accurate as when the GSC10 was measuring wheel revolutions.

    When the GSC10 was working, it was great! Now it is just another irritating piece of non-working electronics. I hope to get it working again. Technology is great. When it works.

  8. #8
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    The GSC10 speed data is only used when the GPS has lost satellite coverage or is stationary, like on an indoor trainer.
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    So if you don't lose the GPS signal while on a ride then the 705 won't use data from the GSC10 sensor? Seems to me that if this were true then it would make no sense to buy a GSC10 sensor if you only use the 705 for riding outside.

  10. #10
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    Quote Originally Posted by Resist
    So if you don't lose the GPS signal while on a ride then the 705 won't use data from the GSC10 sensor? Seems to me that if this were true then it would make no sense to buy a GSC10 sensor if you only use the 705 for riding outside.
    Correct, the GPS only uses the sensor for speed and distance it if looses satellite reception, or if it senses that it is not moving and data is available from a GSC10 mounted on the chainstay with a wheel magnet. I have one on one bike with only the cadence sensor magnet and no wheel magnet.

    Most of us only have the GSC10 because we want cadence data. I do not use it on my two mountain bikes, but have it on my road / tour / commuter bikes. If you are in an area with deep canyons with lots of deciduous tree cover, you might need one. Or, if you ride an indoor trainer and want time/distance data.

    Road riders want to learn to ride a higher cadence, and for that, the GSC10 with a Garmin Edge/Forerunner is very helpful. Some have reasons for wanting cadence on an MTB, but most of us do not.
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  11. #11
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    Gotcha, If I go with the Edge 705 I'll probably go without it at first and see how it does compared to my bike computer. If I see some bad results as you did I'll buy the GSC10 to accompany it.

  12. #12
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    Quote Originally Posted by QuenteK25
    Gotcha, If I go with the Edge 705 I'll probably go without it at first and see how it does compared to my bike computer. If I see some bad results as you did I'll buy the GSC10 to accompany it.
    And if you decide to use the GSC10 as primary data source, you will have to go into the setting and change to "use with GPS off" for the speed / distance pickup of the GSC10 to work. You will need to do this on each ride.

    One trick that most people miss is to turn the GPS on at least 15 minutes before you ride, and let it calibrate the barometric altimeter (if it has one) and get the best satellite acquisition possible while absolutely still. All your data will be much more accurate than if you turn it on and ride away.

    Here is a shot of a commute to and from work. The road running left and right is a four lane (2 each way) road, and the intersection that goes up is a two lane road. You can see my tracks on the shoulder of each road. This is an Edge 305 track downloaded into TopoFusion software, and aerial photo imagery. Is that accurate enough for you?
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  13. #13
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    Quote Originally Posted by slocaus
    And if you decide to use the GSC10 as primary data source, you will have to go into the setting and change to "use with GPS off" for the speed / distance pickup of the GSC10 to work. You will need to do this on each ride.

    One trick that most people miss is to turn the GPS on at least 15 minutes before you ride, and let it calibrate the barometric altimeter (if it has one) and get the best satellite acquisition possible while absolutely still. All your data will be much more accurate than if you turn it on and ride away.

    Here is a shot of a commute to and from work. The road running left and right is a four lane (2 each way) road, and the intersection that goes up is a two lane road. You can see my tracks on the shoulder of each road. This is an Edge 305 track downloaded into TopoFusion software, and aerial photo imagery. Is that accurate enough for you?
    Haha, yeah I'd say that will do

  14. #14
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    Quote Originally Posted by slocaus
    The GSC10 speed data is only used when the GPS has lost satellite coverage or is stationary, like on an indoor trainer.
    Sounds like this is correct. I was searching the Garmin website for help to resolve the non-functioning GSC10 issue I'm having and came across this:
    http://www.garmin.com/garmin/cms/sit.../searchsupport
    Of course, it is lame that it would turn off GPS totally so you can't get the mapping or elevation data.

    Perhaps my issues with accuracy are that I turn it on and start riding the moment the screen turns from "locating satellites" to the normal HR/distance/time. Does it keep working on satellite acquisition after the screen goes to the normal mode?

  15. #15
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    Good job!

    Quote Originally Posted by slocaus
    And if you decide to use the GSC10 as primary data source, you will have to go into the setting and change to "use with GPS off" for the speed / distance pickup of the GSC10 to work. You will need to do this on each ride.

    One trick that most people miss is to turn the GPS on at least 15 minutes before you ride, and let it calibrate the barometric altimeter (if it has one) and get the best satellite acquisition possible while absolutely still. All your data will be much more accurate than if you turn it on and ride away.

    Here is a shot of a commute to and from work. The road running left and right is a four lane (2 each way) road, and the intersection that goes up is a two lane road. You can see my tracks on the shoulder of each road. This is an Edge 305 track downloaded into TopoFusion software, and aerial photo imagery. Is that accurate enough for you?
    YES!

    You are smart! Really great to have you on this forum.
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  16. #16
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    Quote Originally Posted by MultiRider
    Sounds like this is correct. I was searching the Garmin website for help to resolve the non-functioning GSC10 issue I'm having and came across this:
    http://www.garmin.com/garmin/cms/sit.../searchsupport
    Of course, it is lame that it would turn off GPS totally so you can't get the mapping or elevation data.

    Perhaps my issues with accuracy are that I turn it on and start riding the moment the screen turns from "locating satellites" to the normal HR/distance/time. Does it keep working on satellite acquisition after the screen goes to the normal mode?
    You link comes up with a blank support page.

    If you are riding on a trainer indoors, what elevation and mapping do you expect?

    In the three years that I have been using the Edge 305 and reading this forum, it is very very rare to loose signal. I had it happen once, for about 15 feet in a deep canyon blocking satellite view to the south, and heavy sycamore trees overhead. When I downloaed the track, it appeared that I went to the road center and back to the outside when it regained the satellites. I lost accuracy for 15 horizontal feet and maybe 5 feet laterally.... [shrug]

    Look at page 76 of the Garmin 205/305 manual here.
    There are two sensors on the GSC10: one for cadence and one for speed. Cadence data from the GSC10 is always recorded. The speed data from the GSC10 is only recorded and used for distance calculation when the GPS signal is weak or GPS is turned off.
    Yes, but accuracy of satellite acquisition is harder while moving, and never seems to get as precise as when it stabilizes while completely stationary. I let mine get to about +- 15 foot accuracy on the screen before I move it.
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  17. #17
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    Quote Originally Posted by slocaus
    You link comes up with a blank support page.
    Here's the content of the link (did a search on "cadence" and selected one of the topics supplied in the results) which says you have to turn off the GPS entirely to use the GSC10 for speed/distance;

    Question: How do I make my Edge 305 use the speed sensor instead of GPS calculated speed?

    Answer:
    To make the Edge 305 use the speed sensor instead of the GPS for speed tracking, follow these steps:

    Click 'Settings'
    Click 'General'
    Click 'System'
    Select 'GPS' and turn to 'Off'
    This will make the unit to calculate speed using the speed/cadence sensor. Please note: This will also disable the GPS for tracking your location.

    Last modified on: 05/16/2007

    Quote Originally Posted by slocaus
    If you are riding on a trainer indoors, what elevation and mapping do you expect?
    I'm not talking about riding a trainer indoors. Never mentioned that in any of my posts. I'm riding outdoors.

    I've been using my Forerunner 305 for running and biking for several years. But distance wasn't critical to me until this year when I started racing, so I didn't pay attention to accuracy.

    This year, I started racing. I used my Forerunner 305 for the first race of the season -- the Winter Park Hill Climb. It is 5.3 miles of very steep climbing. I planned to go pretty hard until about mile 4.8, then go all out the last 1/2 mile of the race. I led the race up until about mile 3 when a guy passed me. I stayed fairly close to him but tried not to redline my HR until I was confident I could put in a good kick to the end (last 1/2 mile or so).

    Well, my Garmin said "4.6" on Distance as we rounded a corner where people were yelling and screaming "GO! GO! GO!" and there was the finish line about 100 yards away. I got out of the saddle and sprinted like crazy but got 2nd place by 6.8 seconds.

    All because the Forerunner was about a half mile off on the distance traveled to that point.

    I was MOST annoyed at this and bought the GSC10 because I thought it would give better accuracy on speed and distance because the 305 would use wheel rotations and calculate. So this discussion has corrected that misconception.

  18. #18
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    Quote Originally Posted by MultiRider
    Here's the content of the link (did a search on "cadence" and selected one of the topics supplied in the results) which says you have to turn off the GPS entirely to use the GSC10 for speed/distance;

    Question: How do I make my Edge 305 use the speed sensor instead of GPS calculated speed?

    Answer:
    To make the Edge 305 use the speed sensor instead of the GPS for speed tracking, follow these steps:

    Click 'Settings'
    Click 'General'
    Click 'System'
    Select 'GPS' and turn to 'Off'
    This will make the unit to calculate speed using the speed/cadence sensor. Please note: This will also disable the GPS for tracking your location.

    Last modified on: 05/16/2007
    And you will have to do that each time you turn it on.

    Quote Originally Posted by MultiRider
    I'm not talking about riding a trainer indoors. Never mentioned that in any of my posts. I'm riding outdoors.
    I know, My goofball, smartass tendencies keep popping up. This place needs a "tongue in cheek" smilie. The winker just does not convey enough.

    Quote Originally Posted by MultiRider
    I've been using my Forerunner 305 for running and biking for several years. But distance wasn't critical to me until this year when I started racing, so I didn't pay attention to accuracy.

    This year, I started racing. I used my Forerunner 305 for the first race of the season -- the Winter Park Hill Climb. It is 5.3 miles of very steep climbing. I planned to go pretty hard until about mile 4.8, then go all out the last 1/2 mile of the race. I led the race up until about mile 3 when a guy passed me. I stayed fairly close to him but tried not to redline my HR until I was confident I could put in a good kick to the end (last 1/2 mile or so).

    Well, my Garmin said "4.6" on Distance as we rounded a corner where people were yelling and screaming "GO! GO! GO!" and there was the finish line about 100 yards away. I got out of the saddle and sprinted like crazy but got 2nd place by 6.8 seconds.

    All because the Forerunner was about a half mile off on the distance traveled to that point.

    I was MOST annoyed at this and bought the GSC10 because I thought it would give better accuracy on speed and distance because the 305 would use wheel rotations and calculate. So this discussion has corrected that misconception.
    Does the Forerunner have a barometric altimeter? Really steep climbs will affect distance as well, and the barometric altimeter really helps in that regard. Here is a very good thread over on GroundSpeak forums about how the barometric altimeter really works in the Garmin units.
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  19. #19
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    Nope, the Forerunner doesn't have barometric altimeter.

    I am very surprised that the odometer function is so far off on my mountain bike rides. The WP Hill Climb was a gravel road that goes from the base area to the restaurant at the top for delivering supplies. Probably 6-8% grade.

    I just opened up Training Center to see what it thought the grade was on the Hill Climb. Let me assure you, the road that the trucks go up to supply the restaurant don't hit anywhere near a 50% grade. The thing is whacked! Not sure if that contributes to the odometer problem. My Forerunner 305 is significantly short (10%) on mileage for pretty much every ride.

    As you can see, I started to ramp up my effort at 4.5 miles thinking there was 3/4 of a mile left and that I'd really hammer the last 1/2 mile. And then the race was over. Because the Garmin was WRONG. I'm still annoyed.
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