We learned in the “What is OPUS?” tutorial that OPUS, the Online Positioning User Service, generates coordinates from a GNSS data file you provide that are accurate to a few centimeters and consistent with the National Spatial Reference System.

This tutorial describes the basic steps needed to upload a file to OPUS for processing. I’m Mark Schenewerk and I’ll be presenting this tutorial.

Start by opening a browser window and navigating to the National Geodetic Survey’s home page: geodesy - dot - noaa - dot - gov.

{NGS homepage appears}

OPUS is one of the items listed under the “Tools” menu in the banner across the top of the NGS home page. Or, by scrolling down slightly and looking to the left, we see that OPUS is one of the links in the menu of the most popular web pages on this site. Either of these links can be used to navigate to the OPUS homepage.

{OPUS homepage appears}

Before beginning in earnest, let’s examine this web page.

Near the top of the page, messages about recent or pending events might appear. Here we see news about a recent change to the published solution pages.

To the left is a menu of links to other parts of OPUS. Please note the “about OPUS” entry. This is a link to the OPUS online help documentation.

To the right is an icon with the label “sample solutions.” These are links to the online help describing an OPUS solution report.

In the center of the web page is the form used to upload data files for processing.

Now, let’s complete this form in preparation for uploading a data file for processing.

The first field is for the name of your data file. Although you can manually type in the path plus file name, it’s probably easier to use the “Browse” tool. Just click the “Browse” button associated with this field and a file system navigation window opens.

I’ve stored the file we’ll upload under “Downloads” in the “OPUS tutorial” folder. You will have almost certainly stored your data files in another location on your computer. Although your files will be in a different location, you can navigate to them in this way.

I’m going to upload the file ald3 - 320 - r. Selecting the file by clicking on its icon or name, then clicking the “Open” button at the bottom of the window will enter the selected file path plus name into the field for you. You can also double-click the file icon or name accomplish the same.

We see that the file path plus name have been entered.

Before advancing to the next field, note the bold, red text near this and the other fields. These are links to the corresponding sections of the online help documentation describing those fields.

Next, we select the antenna type name using the pull-down menu.

This is a long list of alphabetized names grouped by manufacturer. The name I need happens to be near the bottom of the list: a Trimble - R8 - GNSS3.

Note that to the right of the antenna name is the word NONE. This indicates that there is no radome covering this antenna.

Some antennas can have a separate plastic cover, called a radome, affixed to the antenna while the data were collected. Radomes are rarely used for conventional surveying, but are often used at permanent sites. While the radome helps protect the antenna from the elements, but does have a slight effect on the satellite signals, so it is very important to select the correct antenna plus radome. If you are unsure a radome was used or don’t know the radome type, use the antenna plus NONE.

More information about antennas, including photos and schematics, is found under “Antenna Calibration” listed the “Most Popular” menu on the NGS homepage.

In this case, no radome was used.

Now, I’ll enter the antenna height. This is the vertical height of the antenna reference point, or ARP, above the mark. If you are unsure of the ARP for your antenna type, consult your hardware documentation, talk to your manufacturer or visit the NGS “Antenna Calibration” web page.

For this data, the ARP is the bottom of the antenna, so I’ll enter 2 meters, the length of the fixed height pole.

The last required information is my email address. The solution report will be emailed to this address, so this is a good time to double check this and the other fields.

Scrolling down the page, we see a button labeled “Options.” This button reveals or hides the entry fields for optional information. In most cases, the options aren’t necessary, so we would just leave these fields hidden. But for completeness, let’s click the “Options” button and describe those fields.

A “formats” selection menu allowing you to choose the format and content of your solution report. These formats are described in detail in other tutorials, but to summarize, three choices are available:

standardthe most important information about the solution organized so that it should fit on a single page if printed.

extendedthe standard format with additional information, like base station coordinates and hardware, and covariance matrices appended. The additional information can help you understand your solution in detail or diagnose issues with problem data.

standard + XMLthe standard report with an attachment containing the extended report contents as an extended markup language, or XML, document. Your organization or third parties may provide custom formatting for OPUS reports using the XML document.

We’ll keep the standard format.

Below “formats,” we can specify “base stations” to be used or excluded. You can do this by entering the four-character IDs of the base stations in the left field to specify they be used if available, or enter IDs in the right field to exclude them.

The map icon to the right of these fields opens a window with a map indicating all possible base stations. It takes a few moments to populate, then you can

● pan the map.

● zoom into your region.

● identify a base station.

● and, by clicking on its icon, select it to be used or excluded.

Normally, you should allow OPUS to make these decisions, but there are exceptions. Some projects require specific base stations be used. Or you may be occupying several marks in an area as part of a project and want insure the same base stations are used for all processing. Or you might be aware that a base station is undergoing maintenance, for example, during your project and want to be sure it is not used.

For this data file, I’ll let OPUS choose by leaving these fields blank.

Next, you can select the “state plane” coordinate zone to be used when reporting planar coordinates (if that is possible). You should normally “let OPUS choose,” but here, again, your project may require a specific SPC zone be used, or you may have a project near the boundary of a zone and want to insure that the same SPC zone is used consistently.

I’ll let OPUS choose.

If this data file is part of an OPUS project, you can specify the project in the next field. OPUS Projects is described in other tutorials and won’t be described here.

OPUS remembers nothing about your activities, but if you will be processing several files related as part of a project, re-entering the information for each file can be annoying. For this reason, the next field allows you to create a profile. The profile is associated with your email address and remembers the values entered literally above this field on the form.

I never recommend using a profile. While it can save time, it is easy to forget that you have a profile and that can lead to unexpected results whose cause (the profile) is difficult to diagnose.

If you would like to create a profile, practice a few times, and develop the habit of deleting your profile when you upload the last file in the group.

In this case, I’ll leave it blank. I don’t have a profile and don’t want to create one.

The final option allows me to “publish my solution” if I’d like. Publishing in this way causes OPUS to permanently store your solution and share it with others using the “Published Solutions” link on this page.

There are minimum requirements for a solution to be published and additional information is required. These are described in the online documentation and in the tutorial on publishing through OPUS.

I know this data file does not meet those requirements, so I’ll leave the selection at “No, don’t publish.”

Now that I’ve completed all fields, it’s time to submit the data file and the information I entered. That’s done using one of the two buttons at the bottom of this form.

If your data is between 15 minutes and 2 hours in length, you would click “Upload to Rapid-Static;” if is between 2 and 48 hours in length, you would click “Upload to Static.”

Why is there a choice? GNSS data processing has challenges that are effectively dependent upon the duration of the data set.

Shorter data files require additional information to successfully compute coordinates with reasonable accuracy. Invariably, this means additional, nearby base stations are needed. The availability of these base stations limits the regions from which data collected can be successfully processed. More information about these regions can be found in the online documentation under “Accuracy.” Specifically see the subsection “See precision & availability”.

Longer data files can use the “strength” of the longer time spans to eliminate the need for the additional information. Thus data from almost any location can be successfully processed provided the occupations are 2 hours or longer.

This data file is 2 hour in length, so I’ll click “Upload to Static.”

The upload will complete in a few moments (depending upon your Internet speed). Afterwards, a confirmation page appears. Take advantage of this. I recommend you develop a habit of double checking your

● file name,

● antenna name,

● ARP height

● and email address.

The processing usually completes in a few minutes, but depends upon the number of other uploads active at that moment. When the processing is complete, a solution report is emailed to you. A description of that report is covered in subsequent tutorials.

This concludes the description of uploading a data file for processing. We’ve navigated to the OPUS web pages, defined all fields in the upload form and successfully uploaded a data file for processing. Also, we should now recognize that if we are planning to use OPUS, we’ll need to consider the viability of short occupations and the desire to publish when designing our survey campaign. There are several other tutorials in this series that may be helpful. Links to those tutorials are given at the end of the “What is OPUS” tutorial.