Summary 
Horizontal Accuracy:
RTK: -+1.4cm 68% of the time
RTX: -+2.6cm 68% of the time
Vertical accuracy is generally two times worse than horizontal accuracy so
Vertical Accuracy:
RTK: -+2.8cm 68% of the time
RTX: -+5.2cm 68% of the time

We would not recommend using RTX or similar correction signals for survey as they would likely cost you a lot in extra earth moved because the design will not be correct.

For machine control, we would not recommend also as you will be 'chasing your tail' trying to get the earthworks to balance and you will end up with an inferior finish that will not drain well.

COMPARISON OF POSITIONAL ACCURACY BETWEEN RTK AND RTX GNSS BASED ON THE AUTONOMOUS AGRICULTURAL VEHICLES UNDER FIELD CONDITIONS

ABSTRACT. Currently, many systems (machine vision, high resolution remote sensing, global positioning systems, and odometry techniques) have been integrated into agricultural equipment to increase the efficiency, productivity, and safety of the individual in all field activities. This study focused upon assessing a satellite-based localization solution used in straight path guidance of an autonomous vehicle developed for agricultural applications. The autonomous agricultural vehicle was designed and constructed under RHEA (Robot fleets for highly effective agriculture and forestry management) project and is part of a three-unit fleet of similar vehicles. Static tests showed that 99% of all positions are placed within a circle with a 2.9 cm radius centered at the geo-position using real-time satellite corrections (RTX). Dynamic tests between rows demonstrated a mean (N=610) of the standard deviation for real-time base station corrections (RTK) of 1.43 cm and for real-time satellite corrections (RTX) of 2.55 cm. These results demonstrate that the tractor was able to track each straight line with high degree of accuracy. The integration of a Global Navigation Satellite System (GNSS) with sensors (e.g., inertial sensor, altimeters, odometers, etc.) within the vehicle showed the potential of autonomous tractors for expanding agricultural applications utilizing this technology.

Keywords. Autonomous tractor, GNSS, Precision agriculture, RTK-GPS, Agricultural machinery.

Comparison of positional accuracy between RTK and RTX GNSS gased on the autonomous agricultural vehicles under field conditions (PDF Download Available).

Available from: https://www.researchgate.net/publication/266956117_Comparison_of_positional_accuracy_between_RTK_and_RTX_GNSS_gased_on_the_autonomous_agricultural_vehicles_under_field_conditions [accessed Jul 11, 2017].

Also, see Virtual Reference Station (VRS) for OptiSurface Landform