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Back in the late 1980s, as project manager of the new adjustment of the North American Vertical Datum of 1988 (NAVD88), I worked with federal and state agencies to perform geodetic leveling and replace lost benchmarks. One of the reasons for the NAVD 88 project was to address the issue that thousands of benchmarks placed in previous decades had been subsequently destroyed and many others had been affected by crustal motion, postglacial rebound, and subsidence due to the withdrawal of underground fluids. NGS along with its partners performed thousands of kilometers of leveling to replace lost benchmarks. That said, the loss of control marks, denoted by some as “passive marks,” still seems to be a problem today.

California surveying agencies played a part in replacing and updating lost marks for the NAVD 88 project and it seems that they are doing it again. On Sept. 21, the importance of saving passive marks was discussed at the 2023 CLSA Geomatics Conference at Cal Poly Pomona/College of Engineering.

Defining passive marks

Several of my previous columns have highlighted the new, modernized NGS National Spatial Reference System (NSRS), and how active and passive control will be part of the new system.

For all practical purposes, passive marks are marks that are not continuously operating reference stations (CORS).

On June 22, NGS held a webinar on the benefits and challenges of transitioning to the modernized NSRS at which the presenters were not NGS employees. Users can download the presentation here.

I want to highlight a few statements made by Brian Fisher, director of the American Association for Geodetic Surveying (AAGS). Readers can find more information about AAGS here. First, one of Brian’s slides stated that passive marks retain value and that improving data inclusion is both a benefit and a challenge. During his presentation, Brian stated that “passive marks are always going to have some level of value.” He also mentioned that “NGS has done a great job on improving the data submitting process.” NGS is developing models and tools for users to transition to the new NSRS. Tools such as OPUS Projects aim to help facilitate incorporating passive marks into the new, modernized NSRS.

Brian is not the only one who knows the importance of passive marks. As previously mentioned, the importance of saving surveying control marks was highlighted at the 2023 CLSA Geomatics Conference at Cal Poly Pomona/College of Engineering.

At the conference there was a panel session on saving survey monuments.  

The following is the abstract of the panel session: 

 “To discuss an ongoing problem of the destruction of land survey monuments and what the League of California Surveying Organizations (LCSO) and the California Land Surveyor’s Association are doing about it.” 

The panel consisted of five California County surveyors including David Farrell (LA Deputy County surveyor), Tom Herrin (San Bernardino County surveyor), Michael Lafontaine (Orange Deputy County surveyor), David McMillan (Riverside County surveyor), and Warren Smith (Tuolumne County surveyor). The presentation included discussion of a Monument Preservation Brochure and a Monument Preservation Guide.

Surveyors, engineers, and GIS professionals realize that inaccurate measurements can lead to boundary disputes, errors in construction projects, and environmental impacts. Passive marks are useful for validating measurements and spatial analysis. The panel noted that marks across California are in danger of being damaged or destroyed due to construction or insufficient public awareness. It was noted that addressing the loss of passive marks is important for maintaining California’s geographic information systems and preventing/averting legal disputes.

A goal of the guide is to provide individuals that oversee engineering work with strategies to save passive marks that are important to land boundaries and geospatial data.

The panel realized that survey monument preservation requires a collaborative effort from various stakeholders. By incorporating outreach, accurate locating techniques, efficient reporting systems and meticulous replacement strategies, California can safeguard its survey monuments for current and future generations.

The proposed guide will address the problem and outline a solution. The problem section would include topics such as lack of awareness, inadequate reporting, lack of funding, and the responsibility of the community. I have been informed that the guide will be posted here soon.

The panel members understood that the solution starts with outreach efforts and their draft guide lists the following potential outreach activities:

• Educational campaigns at local schools, community centers, and public events to introduce the importance of survey monuments and their role in land ownership, land surveying and mapping.  
• Community workshops with local civic organizations, homeowners’ associations (HOAs), and chambers of commerce to conduct workshops focused on survey monument preservation. 
• Public awareness materials such as informational brochures, posters, and online resources that explain the significance of survey monuments and the potential consequences of their damage or loss can be distributed through public libraries, city halls, and online platforms. 
• Media engagement with local media outlets can elevate public awareness and reinforce the importance of preserving these markers. 

As part of the public awareness material the group has prepared a draft brochure. They mentioned that having a website, such as the CLSA website, be a hub for contacts and information for research may help support the “save the mark” campaign. They included that GIS web maps will be a common place to find monuments and survey control.

The draft brochure states, “destruction of survey monuments within the public rights-of-way, mainly as the result of public works projects and private developments permitted by public agencies, is increasing, due to a lack of oversight and education concerning the importance of these monuments.”

The draft brochure addresses the following questions:

• What Are Survey Monuments, Bench Marks & Geodetic Control?  
• Why Are They Important?  
• What Can You Do to Preserve Survey Monuments?  
• Who Is Responsible? 
• How Many Survey Monuments Are Really Needed? 

The use of passive marks is well known to land surveyors since they use these marks in their daily operations as described in the statement above. It is crucial to be informed of the importance of passive marks and what they can do to help preserve them. Any professional involved in urban development can have a role in saving passive marks from destruction.

The draft brochure outlines the following actionable steps that others can take: show all existing land survey monuments on improvement plans, grading plans, site plans, etc.; educate engineers, surveyors, plan checkers, inspectors, GIS professionals, and the public about the importance of monuments and the requirements to preserve them; prior to filing notice of completion for any project, have a licensed land surveyor validate that the monuments are in place; and request acknowledgement via a written statement in the permit process, that a licensed land surveyor has performed a field inspection and that no monuments are subject to destruction within the scope of the project, or that existing monuments have been referenced and perpetuated per Business and Professions Code §8771.

The section “How Many Survey Monuments Are Really Needed?” is kept simple and straightforward: all of them! These monuments are set to allow for the retracement (or to mark the location) of features and legal rights on Earth’s surface. 

There are many scientists who believe that active control stations are the solution to the surveying and mapping community’s positioning requirements.  

I believe active control stations such as NOAA CORS Network (NCN) that NGS promulgates are extremely important to the development and implementation of the NSRS. In the new, modernized NSRS access to the geometric component of the NSRS will effectively be defined by CORS and their coordinate functions. That said, this does not diminish the importance and requirement for maintaining and updating the coordinates of passive marks. 

The brochure is still a draft document and was not ready for publication at the time of this newsletter, but I have been told that it will be sent to all California county surveyors with instructions on what the goal is. Also, I have been informed that, as soon as it is publicly available, it will be placed on the websites of the California Land Surveyors Association and The League of California Surveying Organizations. 

I am encouraged by what California surveyors are doing to highlight the importance of passive marks. I would be interested in hearing from others on what they are doing to save passive marks or their thoughts on the importance of passive marks. Please feel free to email me at geospatialsolutionsbydbz@gmail.com. 

On a different topic, I would like to highlight that the NGS has announced the recipients of the NOAA FY 23 Geospatial Modeling Competition Awards. NGS awarded $4 million in grant funding to four institutions — Oregon State University, Scripps Institute of Oceanography, Michigan State University, and the Ohio State University — for projects that will research emerging problems in the field of geodesy, develop tools and models to advance the modernization of the NSRS, and help address a nationwide deficiency of geodesists.   

This is great news for the advancement of geodesy. I will address this in more detail in my November column. 

About the Author: Matteo Luccio

Matteo Luccio, GPS World’s Editor-in-Chief, possesses more than 20 years of experience as a writer and editor for GNSS and geospatial technology magazines. He began his career in the industry in 2000, serving as managing editor of GPS World and Galileo’s World, then as editor of Earth Observation Magazine and GIS Monitor. His technical articles have been published in more than 20 professional magazines, including Professional Surveyor Magazine, Apogeo Spatial and xyHt. Luccio holds a master’s degree in political science from MIT. He can be reached at mluccio@northcoastmedia.net or 541-543-0525.

GPS World Editor-in-Chief, Matteo Luccio, met with Darren McCarthy, aerospace & defense industry segment manager, Rohde & Schwarz, to discuss the company’s new avionics test, developments in using 5G broadcast channels for PNT and more from ION GNSS+ 2023.

Emlid has launched a GNSS receiver, the Reach RS3. It features inertial measurement unit (IMU) tilt compensation and a dual-band radio for enhanced compatibility with third-party receivers.

The Reach RS3 enables users to survey at large tilt angles while maintaining survey-grade accuracy. The multi-band receiver works both as a base and a rover and comes factory calibrated.

The receiver offers versatile options to get corrections from continuously operating reference stations (CORS), another Reach device, or a third-party base, so users can mix and match real-time-kinematic (RTK) receivers in a fleet.

Its NTRIP connectivity enables corrections from CORS, NTRIP service, or a GNSS receiver using Emlid NTRIP Caster. When connected over NTRIP, Reach works on a baseline of more than 60 km in RTK and 100 km in post-processed kinematic. Emlid has launched a GNSS receiver, the Reach RS3. It features inertial measurement unit (IMU) tilt compensation and a dual-band radio for enhanced compatibility with third-party receivers.

The Reach RS3 enables users to survey at large tilt angles while maintaining survey-grade accuracy. The multi-band receiver works both as a base and a rover and comes factory calibrated.

The receiver offers versatile options to get corrections from continuously operating reference stations (CORS), another Reach device, or a third-party base, so users can mix and match real-time-kinematic (RTK) receivers in a fleet.

Its NTRIP connectivity enables corrections from CORS, NTRIP service, or a GNSS receiver using Emlid NTRIP Caster. When connected over NTRIP, Reach works on a baseline of more than 60 km in RTK and 100 km in post-processed kinematic.

About the Author: Matteo Luccio

Matteo Luccio, GPS World’s Editor-in-Chief, possesses more than 20 years of experience as a writer and editor for GNSS and geospatial technology magazines. He began his career in the industry in 2000, serving as managing editor of GPS World and Galileo’s World, then as editor of Earth Observation Magazine and GIS Monitor. His technical articles have been published in more than 20 professional magazines, including Professional Surveyor Magazine, Apogeo Spatial and xyHt. Luccio holds a master’s degree in political science from MIT. He can be reached at mluccio@northcoastmedia.net or 541-543-0525.

Advanced Navigation has opened a new high-tech robotics facility for autonomous systems based at UTS Tech Lab in Botany, New South Wales, Australia.

The facility is designed to boost the manufacturing of the company’s world-first AI navigation systems for GPS-denied environments, including its digital fibre-optic gyroscope (DFOG) technology, Boreas.

Advanced Navigation is one of only four companies across the globe able to manufacture strategic-grade fiber-optic gyroscopes, which are designed to enable reliable navigation for marine vessels, space missions, aerospace, defense, autonomous vehicles and flying taxis.

The new facility will be home to extensive research collaborations between Advanced Navigation and the University of Technology Sydney. The collaborations aim to accelerate the production of new technologies, including its light detection, altimetry, and velocimetry (LiDAV) system, cloud ground control and indoor positioning technology designed to guide visually impaired passengers in underground train stations.

The new facility is aligned with the Australian government’s ongoing commitment towards building a STEM workforce and aims to boost employment in robotics, manufacturing, photonics, mechatronics, mechanical engineering and more.

According to Rokubun — a Spanish company that designs accurate and scalable navigation solutions based on GNSS — released a library solution for decoding and processing Galileo Open Service Navigation Message Authentication (OSNMA) for embedded platforms.

The solution is part of the Horizon Europe BANSHEE project, for which Rokubun served as the coordinating, is EU-funded, and is supported by the European Union Agency for the Space Programme (EUSPA). The goal of the project was to develop a hybrid technology that combines Wi-Fi ranging and satellite navigation (including the Galileo OSNMA) to allow for accurate and seamless indoor-outdoor navigation.

The upcoming Galileo OSNMA will provide authenticated navigation data message against data-level spoofing attacks. By delivering data authentication, the free-to-use Galileo OSNMA assures users that the received Galileo navigation message comes from the system itself and has not been modified by, for example, a spoofing attack.

To address this risk, Rokubun’s library enables the Galileo OSNMA in embedded GNSS solutions. The cross-platform, small-footprint library has undergone extensive testing using official EUSPA test vectors, and all OSNMA algorithms have been validated in real conditions at the European Commission’s Galileo testing facilities located at the Joint Research Centre in Ispra, Italy.

The library is organized to be portable, requiring only a working assembler and C compiler that supports ISO C99. To ensure optimal performance and validate user-specific enhancements, such as the utilization of cryptographic accelerators or other system-on-chip/microcontroller specific resources, Rokubun has implemented a hardware-in-the-loop continuous integration/deployment setup.

This setup continuously tests the library against several reference MCU targets, assessing its performance and guaranteeing its reliability.

NV5 Geospatial, a large geospatial data company, provides services for airport projects across the United States and U.S. territories — mainly supporting airport planning and engineering firms that must meet FAA survey and mapping requirements for data collection at airports. “We generally are a sub-consultant to them, helping them achieve those survey standards for collecting the data and submitting it to the FAA,” said David Grigg, the company’s Aviation Program Director. Typically, this is around planning projects such as airport layout plans and master plans, but also engineering projects such as runway extensions and runway reconstructions.

As an example, Grigg cited the extension of a runway, which requires new flight procedures to be established. “Two survey missions are required for runway extensions. The primary mission is to establish control for the aerial imagery. Using the imagery, control and design data, we check for obstacles photogrammetrically. That data is sent to the FAA and procedures are developed. After construction is complete, we go back to the airport to survey the changed runway and navigational aids (NAVAIDS) to verify that what was designed was ultimately built.”

Another way in which NV5 Geospatial supports airport clients is by conducting obstruction studies around them for vegetation management. “That’s generally where we pull in the lidar surveys,” said Grigg. The FAA’s standards for relative and absolute positioning accuracy for trees are “rather generous” by surveying standards, he said. “We’re talking two to three feet vertically and twenty feet horizontally. It’s not like a typical mapping job where you’re guaranteeing it to one foot or better horizontally and half foot or better vertically.”

The FAA, he points out, has published guidance on how lidar may be used. “We mostly use aerial photogrammetry to support projects in the FAA’s airports GIS program. When we collect lidar at an airport, we do it to generate contours and to identify individual tree canopies. Our lidar-derived data is most often developed to benefit airports for tree mitigation not for FAA airports GIS survey projects.”

On the other hand, the FAA has strict requirements regarding metadata to document when, where, and how each control point is collected. “At the time of the survey, photographs are taken of the GPS units from different angles and cardinal directions,” Grigg said. “This is visual documentation for NGS that the surveyed point is at the location described. ”

Another challenge for surveyors working at airports is that they are required to pull back for incoming aircraft. “Obviously, you will have some logistical issues at busy airports,” said Grigg. Surveyors are required to have special lights and markings on any vehicles that enter the airport property to ensure ground and air visibility. Aircraft movement also impacts surveyors as they must move away from the runway safety area (RSA) for take-offs and landings. Busier airports are surveyed at night, when air traffic is reduced or runways are closed.

A typical project for a small airport takes about nine months, while for bigger airports — such as Chicago O’Hare, Dallas-Fort Worth, or Hartsfield-Jackson Atlanta — they can take up to twice as long. “The large hubs update their master plan on a more reoccurring basis, such as every three to five years,” said Doug Fuller, NV5 Geospatial’s Airport Solutions Specialist. “As the airports get smaller, you start stretching out that timeframe.”

Airport survey requirements

[The following was written by NV5 Geospatial and only lightly edited by GPS World.]

Airports have surveys conducted for many different reasons. However, all survey types require the collection, classification and reporting of accurate data about the project. The methodology selected to gather the information is up to the professional surveyor’s judgment. Some features require observation through ground field methods, while others lend themselves to collection via remote sensing technologies.

All surveys start with a search for existing airport control, which are called Primary Airport Control Points (PACS) and Secondary Airport Control Points (SACS). These are points on the airport that have been adjusted by the National Geodetic Survey (NGS). This ensures that the survey is done on the National Spatial Reference System (NSRS).

A typical survey includes surveying the runway, the end points, any displaced thresholds, and a profile along the centerline of the runway. If the centerline marker is not in the correct location or if it is not there at all, the surveyor will make the necessary measurements to establish the proper location and set a new marker. Next the surveyor must locate all NAVAIDS and survey them at the proper location as described in FAA Advisory Circular 150/5300-18B.

After the NAVAIDS are located, the photo control survey will be done. This still requires the PACS and SACS to be the points of origin of the survey. The base requirement as described in FAA Advisory Circular 150/5300-16C is to survey ten photo control points and five check points. The check points are sent to NGS’s Online Positioning User Service (OPUS). This is used to check that the survey was done on the NSRS and that the compilation meets FAA standards.

The standards the surveyor must meet vary depending on the equipment type or photo control point. Examples of the accuracy requirements for the NAVAIDS are as follows:

Point	Horizontal	Vertical
Distance measuring equipment	+/- 1 ft	+/- 1 ft
Glideslope	+/- 1 ft	+/- 0.25 ft
Inner marker	+/- 10 ft	+/- 20 ft
Localizer	+/- 1 ft	+/- 0.25 ft
Runway end point	+/- 1 f ft	+/- 0.25 ft
Runway profile points	+/- 1 f ft	+/- 0.25 ft
Photo control	+/- 1 ft	+/- 1 ft

PACS and SACS	X	Y	Z	Ellip.
Inverse from PACS to SACS surveyed relative to published	0.09 ft	0.09 ft	0.15 ft	0.13 ft

When surveying on airport property, the largest challenge is always accessing the runway safety area to locate the runway ends and profiles. At small airports Surveyors must work when the runway is not busy; at airports with FAA control towers when the runway is closed. Frequently this is done overnight. Other challenges include access to the FAA NAVAIDS. Some of them must be turned off to be surveyed and others require survey points on which it is not possible to set an instrument. When we are not able to occupy a point, we collect it by surveying multiple equidistant locations around the NAVAID and averaging them.

NV5 Geospatial surveyors use a combination of real-time (R/T) and post-processing techniques. We also use OPUS with the PACS and SACS and the five check points. Once the PACS and SACS have been determined to be stable, the proper coordinates are applied to them and the R/T points are adjusted using Trimble Business Center (TBC). NV5 Geospatial uses Trimble TRM-R8s and we recently added TRM-R12i receivers to our equipment. We use ground control points to orient the photography and to calibrate the lidar.

GPS World Editor-in-Chief, Matteo Luccio, met with John Fischer, resilient PNT and wireless systems, Safran Navigation & Timing, at their booth at ION GNSS+ 2023. Fischer, a GPS World Editorial Advisory Board member, discussed the Minerva Academic Program, the goal of the program and more in this exclusive interview.

“Seen & Heard” is a monthly feature of GPS World magazine, traveling the world to capture interesting and unusual news stories involving the GNSS/PNT industry.

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UK begins UAV deliveries

Royal Mail and UAV company Skyports have launched the Orkney I-Port operation to distribute letters and packages between the Orkney Islands, Scotland, reported the BBC. In partnership with the council’s harbor authority and Scottish airline Loganair, mail will be transported from Royal Mail’s Kirkwall delivery office to the city of Stromness in Orkney. UAVs will then carry items to the islands of Graemsay and Hoy, where postal staff will complete the delivery routes. The UAV service will initially operate for three months and may continue on a permanent basis under existing regulatory frameworks due to Orkney’s unique landscape and the proximity of the islands to one another. The UAV service aims to improve service levels and delivery times to Graemsay and Hoy, as weather and geography typically cause disruption to delivery services. The use of UAVs to deliver mail also may bring significant safety improvements by ensuring that postal workers can deliver between ports without risk.

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GNSS is taking a hike, literally

In July, officials in Taichung City, Taiwan, launched a GNSS-based app to aid lost hikers and to mitigate risk associated with outdoor activities in the area’s mountainous region, reported Tapei Times. The app was developed by the Taichung Fire Bureau in response to a surge in outdoor activities after the COVID-19 pandemic restrictions were lifted and, subsequently, an increase in medical emergencies linked to mountain activities. Wi-Fi towers have been built at major trailheads such as Toukeshan, Anmashan, Fushoushan and Snow Mountain to supplement the app as well as to help facilitate UAV deployment to find lost hikers.

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Lidar reveals Mayan city

In a biological preserve in Mexico’s Campeche state, a team of archaeologists have documented pyramids, palaces, a ball court and other remains of an ancient city they call Ocomtún, reported The New York Times. Archeologists surveyed the site for six weeks in May and June, finding 50-foot-tall structures resembling pyramids, as well as pottery and Mayan engravings they believe date to between 600 AD and 900 AD. The team determined the city was likely abandoned more than 1,000 years ago. Surveying of the area has been revolutionized over the past decade by lidar — allowing researchers to survey densely forested areas that are difficult to explore on foot. Archeologists were able to use airborne lasers to pierce through dense vegetation and reveal the ancient structures and human-modified landscapes beneath.

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Hundreds of UAVs down

More than 350 UAVs were lost during a practice light display show in Melbourne, Australia, on July 14, ahead of a scheduled performance for the opening of the women’s World Cup. The UAVs appeared to stop mid-show and plummet into the Yarra River. Divers have since fished out hundreds of the UAVs. According to the Resilient Navigation and Timing Foundation, the likely cause of the mass-crash was interference with GPS signals.