Grade Field Errors, My explaination

I tried to reply to a previous discussion about this but it was locked.   I saw a comment about going up or down a hill and the Gradient field not being accurate or slow to show the change.  The 1030 Plus, unlike previous models, does not seem to have a barometric altimeter.  Because of this, it relies 100% on GPS to determine the rate of climb or descent. GPS is pretty accurate in showing your horizontal position, within 10-30 feet or so, depending on conditions.  However, if you are talking about 10-30 feet horizontal, that makes the grade field not so accurate. I am sure most of you have experienced on a big climb then topping the hill and starting the downside the grade still shows you climbing.  Without that barometric altimeter, it makes it slower to react.

Another thing about the grade field, from what I have read and what I have experienced, the Garnins calculates the grade this way. 

It records your position every second or so, and then at some predetermined time or distance, it compares your current position to that past position.  It knows how much horizontal distance you have gone and how much altitude you have gained or lost to calculate your grade, plus or minus. That is why your display of grade is always 10-30 feet behind you, depending on your speed.  If you are going up a short/steep hill, and then going down the other side, your display may not even show a hill. Plus, I do not know what the refresh rate is for the display. 

Go up that same hill very slowly, then you will get a more accurate display.  

Many years ago I asked Garmin support about this this and what the "predetermined time or distance" was.  She confirmed that I was correct about how the grade field worked, but she did not know the exact algorithm they used, and it was probably a trade secret anyway.

Just my 2 cents worth.

  • I always thought it was strange that those early docs left off reference to the barometer. It would be hard to calculate grades without it. And when I mark a location that I ride from a lot, it tells me that the elevation is celebrated.  Which suggested the barometer.  But since the 1030 Plus never did a good job of grade, I just thought it was true. My second Garmin was an 705 and an accurate grade was not an issue.  After I had an 800, 830, and 1000 which all did well,  I'm glad that the "gradient responsiveness delay" has been fixed in the 1050 and some of the other models, but so far not the 1030 Plus.  Except for the grade issue, I fell the 1030 Plus has been the best model. 

  • I always thought it was strange that those early docs left off reference to the barometer.

    I doubt the early docs left this out.