CORS network installation kicks off

CORS network installation kicks off

A new project led by the Illinois Department of Transportation is helping improve the accuracy of location data used for surveying, mapping, construction, engineering and a host of other applications.

Over three days in August, IDOT started laying the groundwork to create a network of fixed monuments referred to as Continuously Operating Reference Stations, with installations in Litchfield, Petersburg and Jacksonville. The stations will serve as reliable reference points to continuously record and transmit 3D location data to satellites and other receivers in the area, enabling them to determine their position with greater precision.

The eventual final product: The first free public network of its kind in Illinois. When installations are complete, there will be approximately 70 sites statewide, forming a dense, public spatial network that connects to a Global Navigation Satellite System. These new sites will join roughly 2,000 others across the country that make up the fabric of the national CORS network that supports Geographic Information System applications and other uses.

In addition to IDOT staff, representatives from the National Oceanic and Atmospheric Administration and neighboring DOTs were there for installation day, offering their experience and lessons learned. All told, 30 people took part.

The potential benefits and users are vast.

"Surveyors can tie into this as a benchmark as a very known and very accurate survey monument. They're able to use that information to strengthen the accuracy of their projects," said Dan Mlacnik, engineer of Surveys, Mapping and Modeling in the Bureau of Design and Environment, which is behind the effort for IDOT.

Besides surveying, there are myriad uses for the technology, ranging from automated planting and harvesting to Illinois State Police crash reconstructions. The CORS network also measures tectonic plate movement and will provide valuable information to NOAA's surveillance for the National Geodetic Survey. This is especially important with the New Madrid fault and seismic zone crossing Illinois.

The inconspicuous structures, known as driven-braced monuments, are permanent, deeply anchored tripodal fixtures made of stainless-steel rods drilled 12 feet into the ground at precise angles. Antennae located within the structures are protected by a dome to prevent damage from the elements. The Bureau of Day Labor, IDOT's in-house construction team, is leading the way on construction and has already delivered innovations that will make installations more precise and efficient.

"We'd like it all to be done in the shop as much as possible, so we weld up the top part of the monument in the shop," said Mike McDermott, Operations Supervisor with Day Labor. "We set it in this jig, which actually puts the angles and the form together for us. When we go and transfer the jig out into the field and set it in the ground, we drive these pipes in the exact angle they need to be at. Once we take the jig off, the monument piece slides right on top."

It takes about an hour and a half to drive and weld the pipes once onsite. Day Labor estimates it takes an additional six hours for on-site installation once they are on location.

"Our Day Labor section wanted to streamline this process, and we gave them some plans and specifications for constructing these," said Mlacnik. "They looked at what other states and what other entities had done to build these monuments, and they looked at how they could enhance it. What we were told took other states a couple of hours, we had all four rods in the ground in the precise locations within 25 minutes."

Before any installations could begin on Day 1, it was all hands on deck, inventorying and vetting locations for the monuments, which must meet specific requirements, including a clear view of the southern sky to tie into the constellations of satellites overhead. Roughly 120 IDOT properties were considered initially, including maintenance yards, weigh stations and rest areas. Survey units and survey chiefs in each district aided in delivering on the base site requirements. The Bureau of Information Processing helped procure all the backend infrastructure needed to power the network.

Cassidy Weller, a GIS support technician, gave props to IDOT colleagues for their quick work.

"Operations has been fantastic in providing information on where these CORS sites can go," said Weller. "OP&P has been great too. They're actually the ones that keep track of the facilities for us and got us that information really quickly so that we could start vetting sites. The districts have been super responsive and instrumental in trying to get this up and going. It's a collaborative effort by everyone involved."

The project is made possible by a portion of a $4.5 million federal Advanced Digital Construction Management Systems grant awarded to IDOT in 2023. With matching state funds, the project totals $6.25 million, with CORS being only one facet.

"The Illinois CORS network will be available to the public - we're creating a new public utility," said Weller. "If you have a piece of surveying equipment, if you have a piece of heavy machinery that has automated machine guidance of any kind, whether it be an end loader or a bulldozer or John Deere tractor, if it has this capability where you can press a button and have it follow some sort of preplanned route, you can tie into our network and have it be dead on."