Improving Local GPS Accuracy

[geos715]

The Android as a GPS GeoCaching gaming platform has one major short coming. Frequently waypoints are set and when the game is played, the apparent point may be exactly on target or the apparent point can be 10 or 20 feet off or more in some direction. Every geocacher knows this and accepts this as just part of the game. Recently, a solution to this was suggested by an Android game feature I was developing. I wanted the user to be able to play anywhere. This was accomplished by having the user being able to go somewhere in the world and play the game there and the waypoints in the game would be played in relation to there.

Here's a link to the article:

 

http://tombtalk.net/?page_id=424

 

The Portals game can be downloaded from Android market and you can read about it on Geocaching.com Portals Game GC348FP

 

Perhaps this Improving Local GPS Accuracy technique could be programmed into the Android and IPhone apps from geocaching.

The technique was added so that a multicache could be played anywhere in the world.

[+kunarion]

This part seems flawed:

 

"The only thing that had to be done was take a GPS reading at a known waypoint. The GPS reading on any given date depends upon the whim of the GPS gods and the apparent location is sometimes off by many feet. No matter, I only needed todays apparent location from a fixed point and I had the apparent location for the fixed location. The other waypoints were all in relation to the given point on the measurement day. All I had to do was determine the offset between today and the original measurement day"

 

Indications can swing rather substantially while moving, or even when standing still. If it's an issue of finding out "today's error", that's only a small part of the problem.

Edited September 28, 2011 by kunarion

[+Keelmann And Cici]

So the assumption is the margin of error is fixed (relatively) for the day?

[AZcachemeister]

There are far too many variables (even for a 'regular' handheld) for such a solution to be of significant value.

I could certainly 'calibrate' my GPSr (of any caliber) under perfect conditions at a known location, but as the conditions change, the 'calibration' would become meaningless.

[+dfx]

So the assumption is the margin of error is fixed (relatively) for the day?

 

Sounds like it. A magor fallacy. The coordinate readings at a fixed point can vary greatly over the course of only a few minutes.

[knowschad]

I hate to add to what might appear to be a pile-on, but at the very least, you seem to be disregarding GPS multipath errors, commonly known as "bounce". This can be a huge problem in some areas, and none at all in another area possibly very near by.

 

In addition, a poor satellite "constellation" arrangement yields poor accuracy. It seems to me that getting a fix on a known location does nothing to improve that poor accuracy when it comes to finding another waypoint. Poor accuracy is poor accuracy. But I'm not a GPS expert in the least... I may be wrong, and if you can indeed improve things, more power to you!

[+kunarion]

if you can indeed improve things, more power to you!

I'm probably missing something, but if you have a GPS game that works anywhere, do you need an "accurate" starting point? You just mark whatever spot you're at, whatever the GPS says, and play from there.

[+EdrickV]

I have to say, the basic idea mentioned in the original post sounds a lot like Wherigo to me. Which I know can be setup to do games that use specific coordinates, or "play anywhere" games that apparently use referenced coordinates based on where you were when you started the game. And it's also available for non-Android devices. (Including a couple handheld GPS units.)

 

As far as trying to use something like that to "calibrate" a GPS, Like others I don't think that would work. GPS accuracy is affected by a lot of different factors, some of which are constantly changing. (For example, weather conditions can affect GPS accuracy.) For a real method used to improve the accuracy of GPS units (but, AFAIK, not most smartphones) you could try reading up on WAAS, or GPS III.