Meridian Auto-Averaging

[Guest Firefighter75]

Hello everyone. I've been following the posts for about the last 2 weeks. I'm planning on buying my first GPS and I have decided on the Meridian Gold (I think!). Anyway..I am concerned about the auto-averaging issue. Being a newbie, I have no idea what this feature is. Would anyone care to explain it to me?

[Guest ClayJar]

ically start averaging when you stop moving, you have to make an assumption that if the calculations show you're moving less than X miles/hour, it's just random error and you're actually stnding still.

 

Okay, so that's basically how auto-averaging works, and now here's the problem: When Magellan created the firmware for the GPS 315, they set the threshold speed at about 2-2.5 MPH. So, when you slow down to 2 MPH while hiking up a hill toward the cache, it says, "Oh! He's stopped! Let me average now." Obviously, you haven't stopped, but since they set the threshold speed so high (which was appropriate back when the government was intentionally degrading the civilian signals), the receiver kicks into auto-averaging and therefore your position will start lagging behind where you really are.

 

With the MAP 330 and beyond, including the Meridian series (which seems to be based, in code or spirit, on a modified MAP 330 firmware),the auto-averaging threshold speed is less than 0.5 MPH (it even often displays 0.0 MPH as it goes back to normal mode). This is slow enough that shifting from one foot to the other is enough to kick it out of auto-averaging mode -- it shouldn't ever pose a problem.

 

Incidentally, on a GPS 315, there is a neat little trick to get it to pop out of auto-averaging mode at least momentarily (so it starts over with your current position). You take your receiver and give it a nice, broad swing at arm's length (like you're starting a hula-hoop). When you do that, the receiver will be moving faster than the threshold for about a second, and it'll kick back to normal mode. (I came up with the idea, but someone else named it the "hula-wave", and I actually don't have a GPS 315 to do it with... my MAP 330 and Meridian don't have the problem.)

 

Anyway, so, now you've gotten the basics. Any questions? (My degree is in engineering, not communications, so I may have skipped points. )

[Guest ClayJar]

ically start averaging when you stop moving, you have to make an assumption that if the calculations show you're moving less than X miles/hour, it's just random error and you're actually stnding still.

 

Okay, so that's basically how auto-averaging works, and now here's the problem: When Magellan created the firmware for the GPS 315, they set the threshold speed at about 2-2.5 MPH. So, when you slow down to 2 MPH while hiking up a hill toward the cache, it says, "Oh! He's stopped! Let me average now." Obviously, you haven't stopped, but since they set the threshold speed so high (which was appropriate back when the government was intentionally degrading the civilian signals), the receiver kicks into auto-averaging and therefore your position will start lagging behind where you really are.

 

With the MAP 330 and beyond, including the Meridian series (which seems to be based, in code or spirit, on a modified MAP 330 firmware),the auto-averaging threshold speed is less than 0.5 MPH (it even often displays 0.0 MPH as it goes back to normal mode). This is slow enough that shifting from one foot to the other is enough to kick it out of auto-averaging mode -- it shouldn't ever pose a problem.

 

Incidentally, on a GPS 315, there is a neat little trick to get it to pop out of auto-averaging mode at least momentarily (so it starts over with your current position). You take your receiver and give it a nice, broad swing at arm's length (like you're starting a hula-hoop). When you do that, the receiver will be moving faster than the threshold for about a second, and it'll kick back to normal mode. (I came up with the idea, but someone else named it the "hula-wave", and I actually don't have a GPS 315 to do it with... my MAP 330 and Meridian don't have the problem.)

 

Anyway, so, now you've gotten the basics. Any questions? (My degree is in engineering, not communications, so I may have skipped points. )

[Guest Firefighter75]

Thanks for you help. Now...what I got out of that is auto-averaging in the Meridian is no big deal due to the low threshold and most likely will not confuse the hell out of me while learning how to use my new toy. By the way..your post about your MeriGold helped me pick that unit as well.. Thanks for sharing your knowledge.

[Guest Firefighter75]

Thanks for you help. Now...what I got out of that is auto-averaging in the Meridian is no big deal due to the low threshold and most likely will not confuse the hell out of me while learning how to use my new toy. By the way..your post about your MeriGold helped me pick that unit as well.. Thanks for sharing your knowledge.

[Guest ClayJar]

quote:

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Originally posted by Firefighter75:

Now...what I got out of that is auto-averaging in the Meridian is no big deal due to the low threshold and most likely will not confuse the hell out of me while learning how to use my new toy.

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Yep, that's correct, and I'm always happy to help (um... unless I'm watching a movie or something with J^2, in which case I'll reply when I get home ).