Jacob,

I am aware of the effort but I am not personally involved in 17123. It is typically scientists that are appointed to ISO TC's. I am not a scientist by a long stretch. Clearly Leica is active on the other 17123 TC's so it would make sense to get our group involved.

I am not sure if you have read the papers in the following link...

http://www.mojortk.com/leica-web/app/content/public/resources/files/accuracy/2inch.pdf

If you look at my examples you can see that a Trimble Autopilot running a 332 or 252 receiver is not "sub-inch" at a 1mile baseline 95% of the time. I have several problems with the 'sub-inch' tag. Most companies quote their accuracy at a very short baseline (ie > 1mile) which is simply not representative of the environment these systems will be used. It is OK for surveyors who rarely venture 100 yards from their base but not for farming with people working 10 miles plus from their base.

Secondly, companies quote 1 sigma probabilities (ie 68%). It is simply misleading to use a 2/3rds probability in a non-technical market who most of the time don't understand that there is potential for 1/3rd of the time to be well above 'sub-inch'. Auto-steer is not a stop-start activity like surveying where surveyor can wait for a good fix. Tractors can work 24/7 as you know. This does not get communicated during the sales process. Hence we get people thinking dual frequency RTK is the same as single frequency RTK; or SF2 the same as mojoRTK; or they can't understand why they get blowouts; or they can't understand why they can't get back on track next year.

Just read the confusion in this forum. I cringe at some of the comparisons made between say an outback running WAAS and mojoRTK.

We have taken a risk to quote mojoRTK at 2inches even though it is Leica's survey quality engine which is rated 1/2 inch in the survey world. We have competing sales reps saying "mojoRTK is not true RTK because it is not sub-inch... it's 2 inches". I am sure they believe this wholeheartedly. If you plot the accuracy definitions of the manufacturers you will get charts like these...

http://www.mojortk.com/leica-web/app/content/public/resources/files/accuracy/compare_gps.pdf

In short, I think it would be great for the ISO TC to come up with a suitable standard for ag accuracy, but it should not only be a technical definition that most people will not understand.  It needs a fixed objective standard so that every company states their dynamic repeatable receiver accuracy at a fixed realistic baseline say 10km (6 miles) with a 95% confidence level. For example even changing it to hours-in-the day like +/-2", 23hrs a day at 6 miles range (omit range for SBAS corrections) puts it in terms farmers can apply.   I am worried that "pass-to-pass" accuracy is almost impossible to quantify, especially given the distorting effects the 11 year solar cycle has on this measure.  If someone comes up with a truly objective calculation then I would support it as a 'secondary' measure.

The founder of the Auto-steer market once said to me there is a control systems engineering law "that you can never dynamically control a machine to the accuracy with which you can measure its position".  So in the end your 'on-the-ground' accuracy will always be worse than your reciever accuracy.  So receiver accuracy is probably the place to stay for a standard given the variation of machine/ implement/ steering kit setups.

Let me know if you want to talk more about this topic.

Cheers

John