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LTR usage survey

Back in 2018, we asked QGIS users how often they use QGIS and how often they upgrade. Today, we want to find out more about how different user groups and organisations use QGIS and particularly the LTR. You may be aware of ongoing discussions concerning potentially extending the LTR period and other potential steps to further improve user experience.
To better understand the needs of our QGIS community, we therefore invite you to our new LTR usage survey:

Nyhet från QGIS, orginal inlägg

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InnerSpace location platform supports public safety, COVID-19 response

Photo: Kachura Oleg / iStock / Getty Images Plus / Getty Images

Photo: Kachura Oleg / iStock / Getty Images Plus / Getty Images

Indoor location platform provides municipalities with emergency response and public safety solutions on existing Wi-Fi networks

InnerSpace, a Toronto-based company, is offering its Wi-Fi-based indoor location intelligence platform to support all levels of government. The platform analyzes patterns and movement in public spaces using existing Wi-Fi networks.

The platform is suitable for understanding the movement of people inside public spaces and can support emergency response strategies, social distancing programs and help smart cities implement effective security and public safety measures.

“In response to the global COVID-19 pandemic, we have accelerated the delivery of our public safety solution inFORCE,” said James Wu, CEO, InnerSpace. “Our platform processes RSSI [received signal strength indication] data in real time and returns the industry’s most accurate location data available today. By using public Wi-Fi access points, municipalities have a way to quickly roll out new solutions at city-wide scale.”

InnerSpace inFORCE was selected in a competitive process by the U.S. Department of Homeland Security, for its ability to use Wi-Fi to locate citizens and track emergency responders in an active shooter scenario.

The same platform can be used in a wide variety of emergency situations such as the current COVID-19 pandemic. In addition to the company’s tracking capabilities, it’s analytics dashboard gives public safety offices an unprecedented view into how people leverage public spaces.

“In times of emergency, it is reasonable to prioritize safety and public health to minimize the loss of human life,” said Cerys Goodall, president and COO, InnerSpace. “By providing municipalities with a system that can deliver line-of-sight into how people move in public spaces, we can inform response strategies, improve rescue efforts, and create an infrastructure to support better outcomes.”

InnerSpace inFORCE ingests RSSI data and returns accurate anonymous indoor locations. The information can be connected directly into emergency response communications systems, building management and security systems, or analyzed by InnerSpace to identify critical patterns and trends in people’s movements.

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Gladiator Technologies introduces small, high-performance GNSS/INS

Gladiator Technologies’ low-noise inertial sensor and systems technology coupled with Velox  high-speed processing are now integrated with a 72-channel GNSS receiver to provide compact GNSS/inertial navigation systems (INS) for accurate position, velocity and attitude.

Landmark 60 GNSS/INS. (Photo: Gladiator Technologies)

Landmark 60 GNSS/INS. (Photo: Gladiator Technologies)

The feature set was carefully selected to suit several positioning, navigation and timing (PNT) applications including flight control, navigation and stabilization for imaging, platforms and antennas.

The high-performance LandMark 60 INS/GPS and compact LandMark 005 INS/GPS both feature advanced sensor-fusion technology, combining GNSS position data with Gladiator Technologies’ low-noise, high output inertial sensors as well as barometric pressure and magnetometers.

Both products feature Gladiator Technologies’ proprietary Velox  processing technology and extended Kalman filter (EKF), enabling precision position information during short-term GPS outages.

Velox  Technology combined with the new EKF enable the LandMark  INS/GPS products to have accuracy of less than 2 nautical miles per hour during short-term GPS outages.

Landmark 005 GNSS/INS. (Photo: Gladiator Technologies)

Landmark 005 GNSS/INS. (Photo: Gladiator Technologies)

The LandMark 60 INS/GPS is the top performing unit with +/- 0.3° heading accuracy and pitch/roll angle measurements of 0.1°. It is also available with an option for a real-time kinematic (RTK) GPS receiver.

The small and robust LandMark 005 INS/GPS is less than 35 square centimeters and is suitable for space-constrained applications that require a high standard of INS/GPS performance.

“Our low-noise sensor inputs to the EKF are enhanced by an adaptive estimation algorithm,” said Lee Dunbar, chief software architect. “This, along with extended precision for the nonlinear solution integrator, maximizes the accuracy of position, velocity and attitude. Customer configurable EKF parameters are present to allow optimization for their applications.”

“Leveraging our inertial capability into a complete INS/GPS package was a natural progression for our product line,” said Eric Yates, Gladiator Technologies’ new business development manager. “With the LandMark 005 INS/GPS and LandMark 60 INS/GPS we’re offering an exceptional MEMS-based INS/GPS that fits in the palm of your hand.”

A development kit is available for set-up, configuration and data collection.

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Esri to provide mapping resources to WHO Member States

Advanced geospatial technology offered to global communities during COVID-19 crisisPhoto:

Global mapping company Esri will provide a COVID-19 Response Package for World Health Organization (WHO) Ministries of Health and Global Outbreak Alert and Response Network (GOARN) partners.

The package will enable these organizations to have access to Esri’s geospatial platform and tools that can be used for reporting and analysis of cases and deaths, public health and response activities at the national level, in addition to managing testing sites, community activities and impact, and much more at the local level.

“The intent of our partnership with WHO is about providing technology and capacity building to all the national and local Ministries of Health,” said Jack Dangermond, Esri founder and president. “Having integrated geospatial data and analytics is important to a comprehensive and dynamic response to the rapidly changing situation related to COVID-19. This is particularly true in low resource countries.”

This contribution to the global COVID-19 response will support the digital transformation of global health information systems through mapping and analytics technology. Esri’s geospatial software helps organizations understand complex and vast amounts of data by placing it in a geographic context with sophisticated analysis capabilities such as artificial intelligence (AI).

“While our company has always supported the efforts of governments and NGO’s when facing crises, the COVID-19 pandemic is different and requires a rapid and global response,” said Dangermond. “Our work with WHO is about helping MoHs around the world in equipping and assisting communities with our technology. We strongly believe these efforts will help combat its spread.”

Ministry of Health or GOARN partners can request their COVID-19 Response Package here.

Software access for students

Esri is also providing free access to its ArcGIS platform and learning resources through its website to support college and university students who no longer have access to campus computer labs during the COVID-19 outbreak.

Students will receive access to ArcGIS Online and over 20 apps including ArcGIS Pro, along with a library of lessons to continue their learning and complete courses. Access is available globally to students ages 18 and over.

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US Space Force accepts control of GPS III SV02 amidst global pandemic

The second GPS III satellite, nicknamed Magellan, has been designated healthy and usable.

According to a Notice of Advisory to Navstar Users (NANU) issued by the U.S. Coast Guard, the satellite has been designated usable as of April 1, 1945 ZULU.

The 2nd Space Operations Squadron (2 SOPS) accepted control of the Magellan on March 27 at Schriever Air Force Base, Colorado.

Designated Satellite Vehicle Number 75 (SVN75) in the GPS constellation, Magellan is the second GPS III satellite to be accepted into the program, and the first to be accepted during a global pandemic.

The second GPS III satellite is encapsulated before launch. (Photo: Lockheed Martin)

The second GPS III satellite is encapsulated before launch. (Photo: Lockheed Martin)

“We’re continuing to make major strides even while working through this pandemic, and we continue to expand our capability to further the program along,” said Lt. Col Stephen Toth, 2 SOPS commander. “This is a huge, momentous occasion for us, that we’re reaching this milestone, that our programs are being delivered, that they’re being executed and the systems are performing as expected. Ultimately, we’re all very excited that we’ve accomplished this major milestone in the program’s history, and we’re very excited for the next things to come.”

The new generation of GPS III vehicles have a 15-year design life and signals that are three times more accurate than the current generation.

“[This means users will have] better accuracy anywhere in the world, with a user’s device being able to determine their location more reliably,” said Capt. Ryan Thompson, 2nd SOPS assistant director of operations.

Additionally, the new satellites have eight times improved anti-jam capability, allowing the military warfighter to operate better in contested, degraded and operationally limited environments.

The vehicles are designed to be forward and backward compatible, which allows them to adapt to the future while remaining fully adaptable to the previous generation of vehicles.

Eight more GPS III satellites are scheduled to launch from now until 2025.

Despite any challenges that may arise, 2nd SOPS remains focused on the mission and continues to make history in space.

“As we’ve moved forward into the Space Force, we’ve taken a bigger mindset approach toward being warfighters,” Toth said. “What COVID has actually brought out of us is the full understanding of what it is to operate with a warfighter mindset. We may not be at war with an enemy per say, but we are definitely at war with the virus. My job is to ensure we continue to provide position, navigation and timing to the world. And we take that very seriously, so despite the virus, we’ll ensure that our mission continues.”

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Sewio helps fight COVID-19 with ‘smart quarantining’


Sewio — a UWB-based, real-time location system (RTLS) company — is offering companies free consulting and software licenses to help them install employee tracking technology.

Current quarantining and other enforced measures are designed to save lives by containing the spread of the virus. Once these restrictions are lifted, the pressure to restart manufacturing operations will increase.

Nevertheless, this brings the risk of a COVID-19-positive employee introducing the virus to the workplace, increasing the risk of infecting colleagues, endangering lives and placing the factory under quarantine again.

With its precise accuracy, ultra-wideband RTLS enables employee tracking and monitoring of any employee who has come into contact with a newly identified infected person. According to Sewio, it can help make sure exposed staff members are tested and receive the treatment they need as quickly as possible.

“UWB-RTLS-powered smarter, faster and selective quarantining helps save lives and keep mission-critical operations running at all times,” said Milan Simek, CEO at Sewio Networks.

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Drones equipped with GNSS, inertial a game changer

Why do we keep hearing about unmanned aircraft all the time, almost everywhere? Fortunately, the buzz has gone beyond next-door neighbors flying dangerously close to your roof or hovering annoyingly around a living room window, and incidents of UAV incursions shutting down airports seem to be getting fewer — improved enforcement and higher penalties may be slowing down these incidents.

Now, UAV users are taking on productive, innovative tasks that couldn’t previously be done, or finishing projects surprisingly quickly and more affordably than ever before, with drones built or adapted for new applications. And equipment manufacturers are creating new sensors customized for use on drones.

Commercial, integrated GNSS/inertial sensors are available that have extremely high performance — previously only available with expensive mil-spec electronics — but in lightweight, small packages, supported by real-time kinematic (RTK), precise point positioning (PPP) corrections or post-processed kinematic (PPK). UAVs carry still, video and multi-spectral cameras generating automatically geocoded outputs, ready for post processing into multi-layered formats — virtually everything a customer could ever dream of having. And lidar sensors enable drones to build accurate models of everything they overfly.

Drones originated largely with military forces. Originally used for forward intelligence gathering, UAV tasks have multiplied and substantially expanded in scope.

Commercial industries were quick to realize the benefits. Before drones, the cost of many tasks done manually would be prohibitive and too time-intensive. Fast, affordable data collection now allows us to quickly tackle and solve many problems.

UAVs can pre-survey large, previously inaccessible tracts of difficult terrain, collect detailed visual representations of entire cities, monitor and support crop growth, or even survey underwater terrain using lidar. UAVs provide crop-growing support by flying autonomous patterns and spraying fields with pesticides or fertilizer. They also are being called into service to spray villages with disinfectant to control the spread of coronavirus, and to survey England’s beaches to monitor coastal erosion.

Check out some case studies here:

Featured photo: PhonlamaiPhoto/iStock / Getty Images Plus/Getty Images

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Lidar a viable tool for archeological exploration

PrecisionHawk’s Jaymie Young and Matt Tompkins fly a UAV with the hosts of History Channel’s “Lost Gold of World II” in the Philippines in late 2018. (Photo: PrecisionHawk)

PrecisionHawk’s Jaymie Young and Matt Tompkins fly a UAV with the hosts of History Channel’s “Lost Gold of World II” in the Philippines in late 2018. (Photo: PrecisionHawk)

The collection of about 300 giant geoglyphs known as Nasca Lines were etched into the ground in the Peruvian coastal plain 2,000-years ago by the Nasca culture in South America. They depict various plants, animals, and shapes and are so large that they can only be fully appreciated when viewed from the air. Unlike the Nasca Lines, most archaeological sites are hard to see from the air, especially those deep under thick jungle vegetation, as in the lowlands of northern Guatemala. Here, lidar’s ability to penetrate foliage makes it the ideal tool for archeological exploration. At the same time, the lack of infrastructure, including airports, makes UAVs the platform of choice for many such projects.

Challenges for lidar in archaeology

Operating aerial lidar for archaeology in a jungle environment presents four challenges. The biggest one is penetrating the canopy. “Typically, the sites that they have been exploring lately have been quite overgrown, and disguising what has been there for a long time, to the extent that even someone walking on the ground has not been able to see the scope of the site,” said Paul LaRocque, senior scientist at Teledyne Optech. Penetrating multiple layers of vegetation requires a minimum of two lidar returns. For heavily vegetated environments, Matt Tompkins, director of Flight Services at PrecisionHawk, recommends a five-return system.

The second challenge is ground-truthing the data collected, explained Thomas Garrison, assistant professor in Ithaca College’s Department of Anthropology. “Even though we digitally removed the forest, it is still there, of course.” For example, it is hard to confirm long roads between sites, because they run beyond a ground observer’s field of vision.

The third challenge is acquiring a GPS signal. “In the tropical environment, a UAV needs to return to its take-off site very precisely,” Garrison explained. Finally, jungles put a twist on the familiar trade-offs between fixed-wing and rotary-wing UAVs: “A fixed-wing UAV will cover a greater area, but you may not have enough space for it to take off where you want to fly your lidar and may not be able to recover it,” Garrison said.

Making lidar an effective tool for archaeology required the development of sensors with very high pulse repetition frequencies (PRF) and with multi-look angles, which better penetrate the canopy to reach the ground and any structures, LaRocque explained.

Manned aircraft vs. UAVs

Archaeology missions need aerial lidar sensors with sufficient peak power from each pulse to reach the ground after much of it is absorbed or reflected by the canopy. In this respect, manned fixed- and rotary-wing aircraft have an advantage over UAVs because they can carry larger sensors with a higher peak power. Plus, they can cover much larger areas per flight. “This is important because archaeologists have been finding that [areas of interest] are much bigger than they ever imagined,” LaRocque said.

Finally, forests and jungles make it challenging to find open areas for launching and landing UAVs and flying them by line of sight. “Where do you stand to see the UAV above the canopy?” For these applications, LaRocque said, manned aircraft probably fly just 500 to 1,000 meters above ground level, “because they are not out for high survey efficiency but for penetration to the ground.”

Tompkins, whose company has conducted many missions in jungle environments and other remote places, takes the opposite view. Archaeology constantly presents new challenge and “takes you to some pretty crazy places,” he said and UAV lidar “allows archaeologists to access information that would otherwise be too difficult or dangerous to access.” In the projects on which PrecisionHawk has worked in heavy jungle, it has seen “excellent penetration through heavy jungle canopy, which gave us access to ground-level data,” he said.

Logistically, Tompkins pointed out, UAVs are “significantly easier and safer than manned aircraft” in remote areas with little access to airport infrastructure, air traffic control, and any sort of emergency services. A team with a UAV can mobilize and travel quickly. Where there is no electricity to recharge the UAV’s battery, the team will bring a generator.

Positional accuracy

Archaeological applications do not require survey-level positional accuracy. Archaeologists only need to be able to locate on the ground features that they identify in the 3D lidar point cloud. “We use Trimble Juno 5s, so that we can load the lidar data directly onto their screens,” Garrison said. “If we get near a structure, we only need to take a point. We don’t even need to find base stations and do corrections afterward. We can manually correct the points based on where they were on the structures.”

Ancient structures are rarely in the areas with the thickest, nastiest vegetation, which are usually low-lying areas, Garrison said. However, those areas might reveal other items of cultural interest, such as agricultural fields. “In the lidar data we have, we are seeing that ancient societies were terraforming their entire landscape, so everywhere you go there is something to check or confirm.”


In 2018, PrecisionHawk conducted an archaeological project in a remote jungle in the Philippines for a History Channel show called “Lost Gold of WWII.” Show producers were trying to find where Japanese troops might have stored gold stolen from the Philippine government.The team flew lidar on a UAV to identify roads or other manmade structures that could help them identify possible hiding spots in areas pinpointed through historical documents, Tompkins recalled.The PrecisionHawk team produced a colorized lidar data file in the jungle that the producers used on the program.

The largest lidar acquisition for archaeological investigations in the world is the Pacunam Lidar Initiative (PLI), a consortium of scholars funded by the Guatemalan foundation Pacunam (short for Fundación Patrimonio Cultural Y Natural Maya). So far, the PLI has scanned about 7,000 square kilometers in the lowlands of northern Guatemala.

Garrison is one of three principal consultants for the foundation. “Lidar has a huge impact in archaeology under tropical forests because you get more bang for the buck in terms of peeling back the forest and revealing the preserved ancient landscapes underneath,” he said. “We’ve been working on these data since we first flew in 2016 with the National Center for Airborne Laser Mapping in Houston. We published preliminary results in Science in 2018.” In the massive PLI project, “Instead of just single sites, we can see broad trends across huge areas.”

The first phase of the Pacunam lidar initiative covered 2,100 square kilometers in northern Guatemala in 10 different polygons of data acquisition. “We found that there were 60,000 more structures in these areas than we knew about before,” Garrison said. This raised the question of how so many people could feed themselves. The lidar data revealed that they had used huge swampy areas as agricultural fields. It also revealed many road systems between and within these sites and many defensive earthwork features of military engineering for warfare distributed along the valleys.

“All of that changed our view of what this ancient landscape looked like,” Garrison said. In the summer of 2019, the project flew another 5,000 square kilometers and is now analyzing the data, which shows “a complete picture of an ancient culture’s impact on the landscape,” Garrison said. “When you think of ancient Rome and everything that they had, you can’t really see everything because modern Europe is there. But here we have all this stuff preserved under the jungle in a way that is letting us see the totality of an ancient culture.”

Discoveries made with UAVs

• Using UAV lidar, the Crow Canyon Archaeology Center and the Canyons of the Ancient National Monument were able to map an 800-year-old Pueblo site at Sand Canyon, Colorado, and discover previously undocumented structures. UAV experts from Caddis Aerial and Routescene conducted the survey using a Velodyne HDL32 lidar scanner on a DJI M600 Pro UAV flying at 40-meter altitude relative to the take-off point. They then processed the point cloud, consisting of 3.2 billion points, using Routescene’s LidarViewer Pro software and created a digital terrain module at 400 points per square meter.

• A hexacopter built with DJI technology, flying 20–60 meters above the ground, enabled Isabelle Heitz of AirD’éco to map several ancient sites, including the microtopography of an ancient theater covered by woods in the center of Soissons, a town in eastern France, and a fortified town of the Gallic age, now covered by thick woods.

• Using Google Earth, satellite imagery and low-flying UAVs, archaeologists Sarah Parcak and Christopher A. Tuttle discovered a previously unknown monumental structure that had been hidden in plain sight only half a mile from the World Heritage site of Petra, Jordan.

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The differences between published Geoid18 and Geoid12B values in Southern Louisiana

My February 2020 column provided an analysis of the differences between the latest published hybrid Geoid18 values provided on NGS’ Datasheet and the computed geoid height value using the published NAD 83 (2011) ellipsoid height and NAVD 88 orthometric height. The column highlighted issues on differences due to published heights that have changed since the database pull for Geoid18. It mentioned that future columns will address differences in other portions of CONUS. This column will focus on differences between published Geoid18 values and Geoid12B values in Southern Louisiana. Why are users seeing large differences between the two models?

My last column mentioned that the technical report on Geoid18 provided a good explanation on the stations used in the United States Gulf Coast region. See box titled “GPS on Bench Marks for GEOID18 in the Gulf Coast Region.”

GPS on Bench Marks for GEOID18 in the Gulf Coast Region


There are areas of complex vertical crustal motion in the Texas/Louisiana Gulf Coast region of the United States which render many control station elevations in the region invalid. The selection of GPS on Bench Marks in this region was limited to the small number of marks where the leveling and GPS data agreed to minimize the influence of crustal motion in the hybrid geoid model. Figure 1 depicts the selection of stations used in the hybrid geoid model along the Texas/Louisiana Gulf Coast. (Image: National Geodetic Survey)

Figure 1: GEOID18 Gulf Coast selected marks: There are areas of complex vertical crustal motion in the Texas/Louisiana Gulf Coast region of the United States which render many control station elevations in the region invalid. The selection of GPS on Bench Marks in this region was limited to the small number of marks where the leveling and GPS data agreed to minimize the influence of crustal motion in the hybrid geoid model. Figure 1 depicts the selection of stations used in the hybrid geoid model along the Texas/Louisiana Gulf Coast. (Image: National Geodetic Survey)

As highlighted in the last column, very few stations in Southern Louisiana were used in the creation of the Geoid18 hybrid geoid model. As provided in my last column the box titled “Differences on GPS on Bench Marks in the Gulf Coast Region” depicts the differences between the published Geoid18 value and the computed geoid value using the latest NAD 83 (2011) ellipsoid and NAVD 88 orthometric height.

Differences on GPS on Bench Marks in the Gulf Coast Region

Image: National Geodetic Survey

Image: National Geodetic Survey

The plot indicates that there are many large differences. Many of these differences are to be expected because the Southern Louisiana is an area of known crustal movement. NGS recognizes this and includes the statement below on datasheets for stations published in Southern Louisiana (see box titled “Statement on NGS Datasheet for Stations in Southern Louisiana”).

Statement on NGS Datasheet for Stations in Southern Louisiana

This station is in an area of known vertical motion. Due to the variability of land subsidence, uplift, and crustal motion, NGS has, determined the orthometric heights for marks in these suspect subsidence areas should be considered valid only at the epoch date associated with the orthometric height. These heights must always be validated when used as control. All previously superseded orthometric heights are now considered suspect and are available in the superseded section. NGS does not recommend using suspect or superseded heights as control.

As stated above, Southern Louisiana is an area of crustal movement. There have been many reports that have described the crustal movement in this region. A few examples include “Vulnerability of Louisiana’s coastal wetlands to present-day rates of relative sea-level rise,” “A New Subsidence Map for Coastal Louisiana,” “Spatio-temporal Modeling of Louisiana Land Subsidence Using High-resolution Geo-spatial Data,” “Anthropogenic and geologic influences on subsidence in the vicinity of New Orleans, Louisiana” and “Rates of Vertical Displacement at Bench Marks in the Lower Mississippi Valley and the Northern Gulf Coast.” The figure in the box title “Figure 1 from A New Subsidence Map for Coastal Louisiana,” from a 2017 report, provides an estimate of the subsidence in coastal Louisiana.

Looking at the figure indicates that there is a significant variation of subsidence occurring in coastal Louisiana. The legend indicates that the subsidence rates range between 0.6 to 1.2 cm/year.

The box titled “Excerpt from Anthropogenic and Geologic Influences on Subsidence in the Vicinity of New Orleans, Louisiana” depicts estimates of crustal movement between 2009 and 2012 in the vicinity of New Orleans. Several of the areas in the plot indicate subsidence rates exceeding -1 cm/year. Once again, the figure shows the local variability of subsidence rates.

Last year, NGS performed the Multi-Year CORS Solution 2 (MYCS2). This was described in previous columns, which can be viewed here and here. The MYCS2 process generated computed and modeled velocities for CORSs. The box titled “CORS NAD83 (2011) Vu Velocities” is a plot that depicts the velocities in the “upward” component in cm/year for NOAA CORS that are operational and have a computed velocity in Southern Louisiana. So, what does this mean to estimating a hybrid geoid model in Southern Louisiana?

CORS NAD83 (2011) Vu Velocities

Image: National Geodetic Survey

Image: National Geodetic Survey

The plot indicates that the rates vary from -0.1 cm to -0.8 cm. It should be noted that these stations are CORS and they are typically installed on structures that may not capture the entire amount of subsidence at the land surface. The box titled “CORS Position and Velocity for Station GRIS” provides an example of a CORS sheet from NGS CORS website.

Now, let’s look at differences between Geoid12B and Geoid18 in Southern Louisiana. The box titled “GPS on Bench Marks Used in Geoid18 and Geoid12B” depicts the stations used in Geoid12 and those used in Geoid 18. As indicated in the plots, there were a lot more stations used in the generation of the Geoid12B model than those used to create the Geoid18 model.

GPS on Bench Marks Used in Geoid18 and Geoid12B

Photo: National Geodetic Survey

Photo: National Geodetic Survey

The box titled “Differences between Geoid12B and Geoid18 in Southern Louisiana” provides the values of Geoid12B minus Geoid18 in centimeters on the GPS in Bench Mark stations used in Geoid12B.

Differences between Geoid12B and Geoid18 in Southern Louisiana

Photo: National Geodetic Survey

Photo: National Geodetic Survey

As indicated in the plot, there are some large differences between Geoid12B and Geoid18 values; a few differences exceed 15 centimeters. Based on the previous discussion of crustal movement in Southern Louisiana, this probably shouldn’t come as a surprise. The box titled “Differences between Geoid12B and Geoid18 with Vu Velocity Values” depicts the differences in the hybrid geoid models and the NAD83 (2011) CORS Vu rate.

Differences between Geoid12B and Geoid18 with Vu Velocity Values

Photo: National Geodetic Survey

Photo: National Geodetic Survey

The box titled “Differences between Geoid12B and Geoid18 in Lafayette, Louisiana” depicts the differences in the two hybrid geoid models and the NAD83 (2011) CORS Vu rate values in the Lafayette, Louisiana, region. This region has some of the largest differences between Geoid12B and Geoid18 values in Southern Louisiana. As indicated in the plot, CORS station TONY has a Vu rate of -0.8 cm/year which is fairly large, and the differences between Geoid12B and Geoid18 values are fairly large at the -10 to -15 cm level. Once again, users should expect differences between the two hybrid geoid models because there has been movement in the area and because different GPS on Bench Mark stations were used in the generation of the hybrid geoid models. In the Lafayette region the two stations used in the generation of Geoid18 were not used in Geoid12B (see stations highlighted in a box).

Differences between Geoid12B and Geoid18 in Lafayette, Louisiana

Photo: National Geodetic Survey

Photo: National Geodetic Survey

The box titled “Differences between Geoid12B and Geoid18 in New Orleans, Louisiana” depicts the differences in the hybrid geoid models and the NAD83 (2011) CORS Vu rate values in the New Orleans, Louisiana, region. Two of the same stations that were used in the development of Geoid12B and Geoid18 are highlighted with a box. The difference between the two geoid model values are much less in this region compared with the Lafayette region. The CORS Vu velocities are also less than the CORS station (TONY) value in Lafayette. Saying that, the differences on stations not used in Geoid18 have differences ranging from -4 to -8 cm going southward toward the Gulf of Mexico. Once again, Southern Louisiana is subsiding so these differences are not surprising.

Differences between Geoid12B and Geoid18 in New Orleans, Louisiana

Photo: National Geodetic Survey

Photo: National Geodetic Survey

This means if someone uses NGS’ OPUS web tool to compute a GNSS-derived orthometric height, the NAVD 88 GNSS-derived orthometric height could be significantly different than the published stations in this region. Some of the difference could be due to the difference between the Geoid12B and Geoid18 published values, and some could be due to crustal movement in Southern Louisiana. Saying that, I mentioned in my last column that NGS performed a large GNSS network project in Southern Louisiana in 2016. The GNSS-derived ellipsoid heights were loaded in NGS’ database in March 2019, but the GNSS-derived orthometric height from the 2016 project are not yet finalized so they have not been loaded into NGS’ database. Once finalized and loaded into the database, the 2016 GNSS-derived orthometric heights should be more consistent with GNSS-derived orthometric heights estimated using the NGS’ OPUS web tool. This column focused on differences between published Geoid18 values and Geoid12B values in Southern Louisiana. It provided reasons why users may see large differences between the two models.

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Conducting integrated drone surveys at a congested airport

Photo: Joel Papalini/iStock / Getty Images Plus/Getty Images

Photo: Joel Papalini/iStock / Getty Images Plus/Getty Images

Airports are extremely congested spaces, both on land and in the air, making it difficult to conduct surveys that provide insights into their continued monitoring and maintenance.

UAVs create the opportunity to survey such sites safer and faster, reducing disturbances to everyday operations while collecting a level of detail unparalleled by conventional surveying techniques to locate and accurately capture areas in need of maintenance and management on airport runways.

Following several drainage and grading issues throughout a 650-acre airport, Texas-based civil engineering company Gessner Engineering was contracted to provide surveying services to identify the most problematic regions.

The team had to conduct the survey with minimal impact on runway operations. By coordinating with the airport’s air traffic controllers, the team planned a 6–8-hour flight window, with just a few pauses for ongoing traffic, while the airport operated as usual.

Before the flight, the surveyors used senseFly eMotion flight-planning software to carry out pre-flight risk assessments and plan flights. During the survey, four 20-minute flights were completed with the senseFly eBee fixed-wing drone. With its fully autonomous and easy-to-use aerial mapping capabilities, the eBee was able to capture the high-resolution aerial photos needed to map the entire airport. The data was processed using Pix4D Mapper to generate a topographic model including a point cloud with a ground sample distance of 1.5 inches.

The point cloud was so comprehensive, it brought attention to four more areas with drainage issues, providing a level of detail that would not have been possible using only a ground GNSS base station. The UAV survey took one day, compared to four weeks for traditional surveying. This cut the project time in half and significantly reduced disturbances to airport operations.

“The savings in manpower with the shorter surveying time, accurate data retrieved, and the additional drainage issues identified demonstrate the value of drones, as an enabler of solving complex challenges in congested airspaces, especially where time is limited,” said Troy Hittle, general manager, North America, SenseFly. “The success of this project by using UAV equipment has offered new possibilities to both Gessner Engineering and the future of aviation maintenance.”