VRS (Virtual Reference Station) is a system composed of hardware and software designed to facilitate real-time GPS/GNSS positioning based on a set of reference stations. ODOT utilizes its CORS (Continuously Operating Reference Station) network to perform the role of the reference stations. One primary benefit of VRS is that you don’t need a separate GPS base station and someone to guard it in order to perform RTK positioning across the state. Using VRS, the CORS network acts essentially as a continuous reference station within the entire network. This allows RTK (Real Time Kinematic) positioning using a single (properly configured) rover in the field.
There are multiple brands of GPS equipment that are compatible with ODOT’s VRS network including Trimble, Leica, Topcon, and others. In general, most equipment that can navigate NTRIP can be utilized. Please note that some GPS equipment not originally designed for use with VRS may now be compatible using third party software/equipment.
The NAD83 (2011) horizonatal component of the VRS network is based on the NAD83 (2011) reference frame; 2010.0 epoch, as determined by the NGS.
To utilize this reference frame/datum, please choose one of the following mount points:
The vertical component for all mount points of the VRS network is based on NAVD88, as determined by NGS.
ODOT’s VRS network generates GPS data correction information in CMR+, CMRx, RTCM 2.3, and RTCM 3.0 formats, as well as the ODOT_Ag corrections format that is CMR+ without GLONASS for older Legacy, GPS only units.
The accuracy of ODOT’s VRS has been found to be suitable for many applications. The user should perform their own testing to ensure the VRS will meet the needs of a specific application. Individual accuracies using VRS are a function of many parameters including items such as the equipment, equipment settings, software, GPS/GNSS characteristics, environment, and the procedures being used. All accuracies discussed here are with respect to the reference system, which is the ODOT CORS network in our case. The CORS network is positioned by NGS for various reference frames. See the Datum/Reference Frame section for the current datum/reference frame being used for ODOT’s VRS network.
To obtain access to ODOT’s VRS network, please fill out the form at the link below:
A user “login” and “password” will then be issued for VRS use.