  Differential GPS, commonly referred as DGPS, is a well-known and very
accurate localization system for many outdoor applications in particular for
mobile outdoor robotics. The most common drawback of DGPS systems are the high
costs for both base station and receivers. In this paper, we present a setup
that uses third-party open-source software and a Ublox ZED-F9P chip to build a
ROS-enabled low-cost DGPS setup that is ready to use in a few hours. The main
goal of this paper is to analyze and evaluate the repetitive and absolute
accuracy of the system. The first measurement also examines the differences
between a SAPOS base station and a locally installed one consisting of low-cost
components. During the evaluation process of the absolute accuracy, a moving
mobile robot is used on the receiver side. It is tracked through a highly
accurate VICON motion capture system.
