Thread: So many questions.

Originally Posted by Saitch

They'd have to be perfect conditions then as I was using my Android & the property owner was using his phone, which I have no idea what it was but was pretty flash, & they were both about 100m + out in location in a 600 acre open paddock & as mentioned, I had the benefit of knowing exactly where I was in relation to the Cadastre.
Steve

Hmm maybe something else is going on then.

Stationary in an open field even a "poor" GPS should be able to get a fix better than 100m

Most gps will give a DOP on the Satellite data page.
Looking at it will also let you see the relative position of the "birds".
What you want is a good feed from multiple birds sitting midway between the horizon and straight up (note you can not influence this).

Birds low to the horizon or directly overhead induce greater error in the triangulation.

Originally Posted by FeatherWeightDriver

Hmm maybe something else is going on then.

Stationary in an open field even a "poor" GPS should be able to get a fix better than 100m.

Might be something to do with the datum as Toombie has suggested.

I strongly suspect that for much of the published maps of Australia (whether digital or paper) and even after the speroid and datum are correct, the basic information is often not within 100m. And your identification of features, especially cadastral features, could easily have errors of this sort of order. For example, fences are not necessarily on property boundaries, and roads etc may have been realigned since the map was updated.

John

Agreed (and clarified in my earlier post).

2 possible issues:

• the accuracy of the GPS
• the accuracy of the maps

Originally Posted by Tombie

Most gps will give a DOP on the Satellite data page.
Looking at it will also let you see the relative position of the "birds".
What you want is a good feed from multiple birds sitting midway between the horizon and straight up (note you can not influence this).

Birds low to the horizon or directly overhead induce greater error in the triangulation.

Agreed & with a non dedicated GPS such as An IPad I don't know whether The positions are able to be viewed. Not on my Iphone anyway.
Steve

Originally Posted by JDNSW

I strongly suspect that for much of the published maps of Australia (whether digital or paper) and even after the speroid and datum are correct, the basic information is often not within 100m. And your identification of features, especially cadastral features, could easily have errors of this sort of order. For example, fences are not necessarily on property boundaries, and roads etc may have been realigned since the map was updated.

John

John, I was pretty sure where I was as I'd located, by survey, 4 pegs & 4 recovery marks placed in the early 90's & even with a scale factor applied, the phone position would still be poor.
Steve

Originally Posted by Saitch

Agreed & with a non dedicated GPS such as An IPad I don't know whether The positions are able to be viewed. Not on my Iphone anyway.
Steve

I'm pretty sure IPhone's don't make detailed GPS data available. What you get is what you get.

Android devices, on the other hand, allow full access so you can see what satellites you are seeing, signal quality etc.

This is what I get sitting in my house... please don't tell anyone where I live

Originally Posted by V8Ian

Thanks Tombie, you good for coffee on the way home?

No worries mate... Coffee, chat... Welcome to drop in...