GPS Coordinates Freeze, Does this happen with every GPS?

[unity007]

Hello,

I'm fairly new to geocaching, but when I go out trying to find a cache, my GPS unit will work when I'm in motion, but the second i stop moving and try to search, or walk slowly, my unit stays stuck on previous coordinates.

 

This has made finding even simple caches incredibly difficult and frustrating, and is actually turning me off from caching altogether. Does this happen with every GPS device? Right now I'm using a Mio Moov, and unfortunately I don't really have it in my budget to buy a state of the art GPS.

[+ecanderson]

Hello,

I'm fairly new to geocaching, but when I go out trying to find a cache, my GPS unit will work when I'm in motion, but the second i stop moving and try to search, or walk slowly, my unit stays stuck on previous coordinates.

 

This has made finding even simple caches incredibly difficult and frustrating, and is actually turning me off from caching altogether. Does this happen with every GPS device? Right now I'm using a Mio Moov, and unfortunately I don't really have it in my budget to buy a state of the art GPS.

There is always a little bit of "coordinate drift" when you stand still - and your Mio is trying to avoid showing that drift. It's probably also trying to hold you to a road position when you're near one. It's not an ideal device for what you're trying to do in many respects. "State of the art" is in the eye of the beholder. There are a number of fine GPS units out there that you could pick up used for very little money. Check the Garage Sale area here. You might be surprised. Any of the older eTrex models with a high sensitivity chipset (typically indicated by an "H" in the model suffix, or a GPSMAP series unit with an "x" in the suffix) would get you started. Paperless is nice (and more $), but not essential. I found my first 2000 without that feature. Edited February 26, 2011 by ecanderson

[+StarBrand]

All smaller GPS units have an accuracy error to any reading in the 15 to 30 foot range. Small movements do not always get noticed by the unit as well (sometimes as much as 20 feet). Once you get inside of the error radius, you will often see a lot of strangeness to the readings as they shift seemingly randomly around. Put the GPS away and start looking for likely hiding spots.

[+ecanderson]

Put the GPS away and start looking for likely hiding spots.

Since that's an automotive GPS, it might not even get him that close due to "road snap" issues.

 

To the OP - there are very few automotive GPS units that are really good for geocaching - even when you discount the battery life and durability issues.

Edited February 26, 2011 by ecanderson

[+dfx]

Not every GPS does it, it depends on the type of GPS chip and how it's configured, and also on the software used.

 

Most or probably all GPS chips can be configured to constantly report updated coordinates, meaning that every time they deliver a set of coordinates (usually once a second), they will deliver their current "best guess" on the current location, which will always slightly vary. To the user it will appear that the coordinates are always jumping around and moving around a bit, which can make pinpointing GZ somewhat difficult (even though technically, this way you get the most information). This is a why certain software and firmware (I believe Garmin handhelds are doing it this way) are "smoothing" out the raw data from the GPS chip, to make it appear more steady to the user and make it more useful by being more intuitive. The downside is that if the algorithm isn't perfect (and it never is), the position will stop updating under certain circumstances, which can be quite annoying. The movement knows as "hula wave" can sometimes be used to remedy this and get updated coordinates again, or otherwise simply waiting it out can also work.

 

The other option is to offload this job to the GPS chip itself. This is known as "static navigation" and causes the GPS chip to stop delivering updated coordinates once it has detected that it stopped moving with a certain amount of confidence. The effects (and potential remedy) is similar to when the software is doing it, only that in this case, the software has no say in the matter and has to trust the GPS chip to do the right thing (which it may or may not do). Vehicle GPS devices often use the static navigation feature of the GPS chip to make things simpler and because it's good enough for vehicle navigation purposes. Those units also often have the mentioned "road snap" problem, which isn't directly related to the GPS data, but makes geocaching with them very hard to impossible.

Edited February 26, 2011 by dfx