OPUS Processing with Emlid Reach

Here is a quick tutorial on using the National Geodetic Survey’s (NGS) Online Positioning User Service (OPUS) with multi-band receivers like the Emlid Reach RS2+, Emlid Reach RS3, and Emlid Reach RX. This high-accuracy workflow is uniform and can be adapted across any alternative survey-grade GNSS receivers to achieve precise geographic constraints.

NOAA's OPUS provides completely free access to high-accuracy geodetic coordinates, running the exact same backend engine software used to calculate coordinates for the permanent CORS (Continuously Operating Reference Stations) network. This guide breaks down exactly how to collect your static point raw data and submit it online.

Step 1: Preparing Your Base Logging Profile

Before heading out to set your equipment up, verify your structural base configurations. Measure and take careful note of your true physical pole height, then open your hardware settings menu in Emlid Flow. Emlid features a dedicated, native OPUS logging preset that automates your data configuration to output the exact recording structures required by the NGS server.

• Enable AutoStart: Toggling this on ensures that your base receiver initializes data logging immediately upon powering up, allowing you to focus entirely on setting up securely over the physical marker point.
• Enable Backup Data for RINEX: This is a crucial safety step. The default OPUS recording preset isolates and logs frequencies only from the NAVSTAR GPS constellation. Enabling the complete RINEX backup ensures that you retain multi-constellation data (GLONASS, Galileo, BeiDou) across that timeframe in case you need to run independent post-processing later.

Step 2: Field Data Collection Guidelines

For this walkthrough scenario, we are setting up our receiver over a physical survey stake tack monument on the ground. We plan to establish this point as a recurring, permanent baseline location for our field job site in the future, making a precise OPUS coordinate solution absolutely necessary.

OPUS processes your submitted data log through two distinct tracking modules based on the total duration of your continuous continuous session. While the absolute system minimums are shorter, our engineering group highly recommends expanding your observation times in the field to secure solid baseline results:

• Rapid-Static Collection: Recommended minimum of 90 minutes continuous logging.
• Static Collection: Recommended minimum of 4 hours continuous logging.

Step 3: Downloading and Submitting Logs to the Web

When using an Emlid Reach RS2+ or RS3 with the native OPUS tracking preset active, your compatible observation files will be cleanly compiled inside your receiver's internal RINEX directory.

💡 Log Extraction Note: If you are unfamiliar with the steps to pull data off your device locally, consult our tutorial on how to download log files from your Emlid Reach receiver directly to your computer.

Locate your observation log file containing the specific date extension suffix (for instance, .230) and select it inside the OPUS web upload window. Next, follow these input steps:

1. Select your exact receiver antenna type profile from the drop-down menu list to ensure your solution incorporates proper phase center variation formulas.
2. Input your precise, true physical pole height measurement.
3. Pick the applicable processing tier—either Static or Rapid-Static—based directly on the total continuous time duration of your data collection.
4. Enter your email address and click upload.

Step 4: Interpreting Your Solution Page

Upon successful document transmission, the OPUS platform will present an on-screen validation confirmation message. Once calculated, your final automated report sheet will arrive directly in your email inbox.

If your file contains an adequate signal-to-noise ratio and clean tracking data, you will receive a standard text solution sheet. The left column items outline your highly precise, solved absolute point coordinates referenced to the NAD_83 datum framework. The right side layout details deep analytical information regarding the surrounding specific CORS base stations selected by the NGS engine to tie down your point.

If the data contains corruption or processing errors, the returned email will detail the specific mathematical failure logs. Most commonly, if you attempt to upload a tracking file immediately after turning off the base in the field, the server may fail to resolve a solution; this occurs because the local CORS network stations require up to 24 hours to elapse before their corresponding tracking data logs are fully indexed and available to the OPUS server.