Q Do I need to pay to use MoDOT’s VRS GNSS system?
A

No, it is a free network.

Q How do I access the system for Real time corrections?
A

Go to https://gpsweb3.modot.mo.gov/ and download and fill out the User Agreement.  Once completed, with notary stamp send it in and MoDOT will enter the information, then grant you access.  You will receive an email with all your credentials to use the Network.
Q What does the access get me?
A

You will have access to real-time corrections at your GNSS rover when connected to our Real-Time Network (RTN) via cellular communication services.
Access to Rinex Data files for post-processing of static GNSS observations from the Reference Data Shop on the webpage.
Plus, Trimble specific users can access an addition service from our Reference Data Shop called Virtual Reference Station (VRS), which allows the user to generate a VRS file for at a specific location.

Q Do I need a specific brand of equipment to access the system?
A

No, the network will work with many brands of receivers. We provide GNSS data in several formats: RTCM2.1, RTCM2.3, RTCM3.1, CMR+, CMRx, and RTCM3Net_Autocell.  Consult your dealer as to which message format will work best with your equipment.
The Radio Technical Commission for Maritime Services (RTCM) sets the standards.  This message type is an open source message that is understood by most GNSS receivers.  This is recommended by most dealers other than Trimble.
Compact Message Record (CMR) is a correction proprietary to Trimble.       

Q Do I need a dual frequency receiver to access the data?
A

No, you do not.  If you want accuracies in the range of 2-3cm you will need a dual frequency receiver.  If your accuracy requirement is in the 1-meter range, then you can use a single frequency receiver.  You will need to check with your dealer to check the compatibility of your equipment.
Q My company has multiple receivers; do I need to send in Access Agreements for each receiver?
A

No.  You get the ability to run multiple receivers, using the same user name and password, at the same time with each access we grant.  It is best to submit the agreement under the name of an owner or officer of the company so that you don’t lose access if an employee quits.  We suggest that each separate office has their own user name and password.  We require dealers to have the end user fill out the agreement and not use one blanket user name and password.

Q What Horizontal and Vertical Datum does the MoDOT VRS GNSS network use?
A

The VRS mountpoints will provide corrections consistent with NGS’s NAD83(2011) Epoch 2010.00 adjustment.  To get NAVD88 elevations from the NAD83(2011) ellipsoid heights you should use the latest Geoid model from NGS.   https://www.ngs.noaa.gov/GEOID/GEOID12A/
Q Do I need to do a calibration/localization? 
A

If you want your survey to match the local control as close as possible, you might want to do a calibration.  Contact your equipment dealer as to how to do one with your equipment.
Q Do all the stations also use Glonass satellites?
A

Yes, all the stations in MoDOT’s VRS network utilize Glonass satellites. We are adding Galileo slowly around the state as budget permits but are not fully capable currently.
Q How far can I work outside the network of base stations and still get survey grade corrections?
A

The software specifications say that you are safe to use the network within 10 miles of the exterior stations.  You can still receive corrections considerably further outside than that, but you should be more diligent in checking into know control in order to meet the accuracies of your survey.
Q What cellular provider works best with the network?
A

This is one that would best be answered by your dealer or other users in your area.  They would be able to tell you what plan you would need and what provider works best in the area you would work in. 
Remember that GNSS coverage in your area does not mean that you will have cellular coverage and be able to use MoDOT’s VRS network.  You need both for this RTK method to work. 

Q What should I expect for downtime with the network?
A

The network consists of 80+ GNSS stations, servers and software, plus it connects to end users via the internet and cellular communication. We strive for a 100% uptime for the network but realize that this is not possible.

Q How can I contact MoDOT if I am having a network issue or a question about the network?
A

If you have general questions about the network, you can email us at gpsnetwork@modot.mo.gov.  If you are having issues and need assistance you can call our operator at 573-751-5000.  Tell them that you are having a Network issue along with the general nature of the problem.  We will receive a support ticket and contact you.    You can receive text messages from our Twitter account by texting ‘follow ModotGPS’ to 40404.