Thread: GPS accuracy

Originally Posted by ghand2

Have been using Oziexplorer on my note book with a with a magnetic base receiver (BU-353) for my touring. I recently used it to make a route around my farm for crop spraying with my tractor & boom spray. Plotted a blank map with parallel lines 12meters apart. After a bit of practise I managed to keep on track reasonably well when spraying.
Does anyone know of a way of increasing the accuracy of this set up.
Geoff.

I don't know of any direct answer to this relating to GPS but colleagues of mine are involved in university research on Precision Farming. I guess if you google "precision Farming" this may show some pages with inf you are looking for. My understanding is that it involves spraying but also fertiliser application etc. Just a quick search of the uni website revealed these links.

On another non-GPS track... I have seen sprayers over here (in NZ) use a foaming tip on the ends of their booms. The foam builds up on the tip over 6-10 metres of distance and then drops to the ground, this leaves blobs of foam on the ground on the outside of the sprayed area. They can then turn around and come back seeing where they have been.

Pretty sure that any 'precision' work will need the use of an additional GPS signal from a fixed (known location) ground station operating along the lines of differential GPS.


Martyn

Originally Posted by Bushie

Pretty sure that any 'precision' work will need the use of an additional GPS signal from a fixed (known location) ground station operating along the lines of differential GPS.


Martyn

Exactly what Survey use at the mine.

We have a few fancy Trimbles at work and the accuracy is under 30 cm but you are talking expensive gear (see GeoXH handheld computers from Trimble Australia and Hand-held Ranger field computers from Trimble Australia). Most 'ordinary 'GPS' including those in your iPhone and the like, are reliable to about 10 m. Couple critical issues are repeatability (does the GPS give the same coordinates for the same location every time you use it); and how 'accurate' the ground control, map or plan to which you are cross referencing it to, is. Added to that, obviously the more satellites you pick up the more accurate the output. However, tied with this is that GPSs like Trimbles pick up additional satellites that your normal GPS cannot. Also, the algorithms (programs if you like) that a Trimble would use would be far more complex and require significant addition 'computing power' to undertake the 'calculations'. But back to the original question, rather than a GPS jerry built approach, have a look at this Trimble approach: Spray control systems from Trimble Australia . Would not be cheap, but may achieve what you are seeking.

Cheers
KarlB

Here is another option and its good for both on the street and in the paddock!

Leica mojoMINI

My Garmin Colorado will get 3m radius in standalone or down to 1.5 - 2m with an external antenna.

Try installing the antenna on the roof of the sprayer, will get better reception than being in the cab or on the dash.

Originally Posted by Bushie

Pretty sure that any 'precision' work will need the use of an additional GPS signal from a fixed (known location) ground station operating along the lines of differential GPS.


Martyn

I thought differential GPS became obsolete when the Yanks removed the built in inacuracy from the system.

Deano

Originally Posted by DeanoH

I thought differential GPS became obsolete when the Yanks removed the built in inacuracy from the system.

Deano

Depends on what you are using it for. For mobile positioning, an accuracy of 6m is routinely achievable without differential positioning, but better than this requires a differential signal. For fixed positions, centimetre accuracy is achievable by recording signals over several hours and post processing without differential GPS. Both these figures assume good satellite geometry and adequate processing power not to have too many shortcuts in the algorithms used.

These are more accurate than most maps.

John