Surveyaan: Drone Survey & Mapping Solutions - Blog #errors

Mastering Tilt Compensation in DGNSS: Why It’s a Must-Know for Today’s Surveyors

Wed, 02 Jul 2025 10:44:52 +0000

Surveying is built on precision. A few centimeters can make or break a boundary line, construction layout, or mining volume calculation. Traditionally, Differential GNSS (DGNS) receivers required the pole to be held perfectly vertical to ensure accuracy. But in real-world environments — uneven terrain, obstructed areas, or busy sites — that’s not always feasible.

The Traditional Challenge
Traditionally, achieving high accuracy with GNSS required meticulous leveling of the receiver pole. Any deviation from vertical introduced errors in the measured horizontal position. Surveyors had to constantly adjust the pole using levels and tripods, which could be slow and frustrating, particularly when:
  1. Working on uneven ground.
  2. Measuring points in hard-to-reach locations like building corners or under obstructions.
  3. Conducting large-scale surveys requiring numerous measurements.
This need for constant leveling not only reduced productivity but also increased the physical strain on surveyors.

What Is DGNSS Tilt Compensation?

Tilt compensation allows a GNSS receiver to accurately record positions even when the pole is not held vertically. This is made possible by integrating sensors like IMUs (Inertial Measurement Units) into the receiver, which calculate the tilt angle and correct the final coordinate accordingly.

Instead of worrying about bubble levels or perfect posture, the system does the math for you — making your workflow faster, easier, and safer.

How Does DGNSS Tilt Compensation Work?

When tilt compensation is enabled, the DGNSS receiver continuously monitors its tilt angle and direction. Combined with the GNSS positioning data and the known height of the pole, the system uses trigonometric calculations to determine the true horizontal position of the point being measured. This eliminates the need for the user to meticulously level the pole for each measurement, significantly increasing efficiency and ease of use.

Why Tilt Compensation Matters

Faster Surveys: No need to spend time leveling the pole before every measurement. Tilt-compensated receivers allow for faster point collection, especially in high-volume or rugged environments. Measurements can be taken much faster as there is no need to level the pole precisely. Some manufacturers claim up to a 20% increase in point measurement efficiency and a 30% improvement in stakeout productivity.
Safer Data Collection: In areas like open-pit mines or construction sites, it’s not always safe or practical to reach the exact location of a point. Tilt compensation enables surveyors to collect data from a safe distance while maintaining accuracy.
Improved Accuracy on Slopes and Obstacles: Surveying in sloped or obstructed areas is much easier with tilt compensation, reducing both human error and the time spent re-collecting points.
Reduced Fatigue: The physical strain of trying to keep the pole perfectly vertical for extended periods is reduced.
Calibration-Free Options: Some advanced systems with IMUs offer calibration-free tilt compensation, making them ready to use immediately.

Why Tilt Compensation Matters
Whether you’re a beginner or a seasoned surveyor, tilt-enabled DGNSS can improve your workflow in many environments:
Mining: Safely survey benches and edges without going right to the edge
Construction: Quickly map out features like corners, manholes, or rebar points
Urban Surveying: Reach tight spots near fences, walls, or parked vehicles
Agriculture: Handle sloped fields without worrying about pole leveling

Is Tilt Compensation Accurate?

Yes — and then some. High-quality DGNS receivers with calibrated IMUs can provide centimeter-level accuracy even when tilted up to 60°. Of course, performance depends on sensor quality, GNSS signal strength, and environmental factors — but for most professional tasks, tilt compensation is not only sufficient — it’s essential.

Tilt Is the Future of Efficient Surveying

Tilt compensation isn’t a luxury feature anymore — it’s becoming a standard expectation in professional GNSS systems. By reducing physical strain, increasing safety, and speeding up workflows, it empowers surveyors to work smarter and safer.

Tilt compensation has revolutionized field surveying by improving safety, speed, and flexibility — without sacrificing accuracy. With devices like the SurveyPod DGNSS, surveyors can now handle complex environments more confidently and efficiently.

If you’re still leveling your pole manually at every point, it might be time to experience the benefits of tilt for yourself.

This brings us to the end of the blog. I hope this article gained some knowledge for you!
Thank you for reading.

About SurveyGyaan

SurveyGyaan is an educational initiative under the Surveyaan brand, which is a subsidiary of Nibrus Technologies Private Limited. Surveypod specializes in DGNSS/DGPS manufacturing in INDIA.

Surveypod: www.surveypod.in

Surveyaan: www.surveyaan.com

The Importance of IMU in GNSS: Enhancing Accuracy Reliability

Wed, 30 Apr 2025 11:17:09 +0000

Global Navigation Satellite Systems (GNSS) like GPS, GLONASS, Galileo, and BeiDou provide essential positioning data for navigation, surveying, and autonomous systems. However, GNSS signals can be disrupted by obstacles like buildings, tunnels, or dense foliage. This is where an Inertial Measurement Unit (IMU) becomes crucial.

In this blog, we’ll explore the importance of IMU in GNSS, how it enhances accuracy, and why it’s a game-changer for high-precision applications.

What is an IMU?

An Inertial Measurement Unit (IMU) is an electronic device that measures acceleration, angular rate, and sometimes magnetic field using a combination of accelerometers, gyroscopes, and magnetometers.

Key Components of an IMU:

Accelerometers — Measure linear acceleration.
Gyroscopes — Measure angular velocity (rotation).
Magnetometers (optional) — Detect Earth’s magnetic field for heading reference.

IMU + GNSS: A Powerful Combination

GNSS provides accurate absolute positioning by triangulating signals from satellites. However, it has limitations, such as:

Signal loss in urban canyons, forests, or tunnels

Latency and lags in fast-moving environments

Susceptibility to multipath errors

By integrating an IMU, GNSS receivers gain inertial data, which helps:

Bridge signal gaps when satellites are temporarily lost
Maintain positioning accuracy during high dynamic motion
Provide smooth and continuous data streams even in GNSS-denied environments

Key Benefits of IMU in GNSS Systems

1. Improved Accuracy and Reliability : When GNSS signals degrade or drop, the IMU keeps tracking the position through dead reckoning, minimizing errors in output data. This is vital in drone surveying and autonomous systems.

2.Real-Time Orientation and Attitude : IMU provides pitch, roll, and yaw data — crucial for accurate georeferencing of aerial imagery, especially in photogrammetry and LiDAR missions.

3. Integrated RTK : Real Time Kinematic (RTK) is a technique that uses a reference station (base) to provide corrections to the GNSS receiver, resulting in sub-centimeter level accuracy. Many GNSS IMU systems have integrated RTK capabilities, allowing for even higher accuracy navigation solutions.

4. Enhanced Mapping Precision : In applications like corridor mapping, road surveys, or construction monitoring, IMU ensures accurate heading and tilt correction, resulting in cleaner, more precise data.

Disadvantages of IMUs

The following are some of the disadvantages of IMUs:

1. It can drift over time : The accuracy of IMU measurements can degrade over time due to drift, which means that the IMU may slowly lose its ability to accurately measure the object’s orientation, velocity, and acceleration.

2.They are susceptible to noise : IMU measurements can also be affected by noise. This noise can come from various sources, such as vibrations, electromagnetic interference, and temperature changes.

3. Require calibration : IMUs typically require calibration to ensure that they are providing accurate measurements. This calibration process can be time-consuming and complex.

Applications Benefiting from GNSS + IMU Integration

1. Drone Mapping & Aerial Surveying : Ensures accurate image geotagging and stable flight control.

2.Mobile Mapping Systems : For land-based vehicles mapping roads or railways.

3. Autonomous Vehicles : Essential for navigation without full GNSS visibility.

4. Agriculture & Mining: Enables reliable operation in harsh and obstructed environments.

5. Marine Navigation : Stabilizes heading and pitch in wave-affected areas.

The integration of IMU with GNSS is critical for high-precision, reliable, and continuous positioning in dynamic and signal-challenged environments. Whether for autonomous systems, drones, or surveying, an IMU ensures that navigation remains accurate even when satellite signals are unavailable.

For industries requiring uninterrupted and precise positioning, a GNSS + IMU solution is indispensable.

This brings us to the end of the blog. I hope this article gained some knowledge for you!

Thank you for reading.

About SurveyGyaan

SurveyGyaan is an educational initiative under the Surveyaan brand, which is a subsidiary of Nibrus Technologies Private Limited. Surveyaan specializes in drone manufacturing and the development of photogrammetry software.

Surveypod: www.surveypod.in (DGNSS Manufacturer Website)

Surveyaan: www.surveyaan.com (Drone Manufacturer Website)

Surveyaan Geoworkspace: app.surveyaan.com (Cloud Photogrammetry Software Website)

Best Practices for DGNSS (Differential Global Navigation Satellite System)

Thu, 10 Apr 2025 09:17:32 +0000

Systematic field procedures are part of any successful DGNSS survey that guarantees that data obtained is both accurate and reliable. Whether in terms of setting up base and rover stations or the field procedures and collection of data, the same case applies — best practices ensure results are both accurate and reliable. This blog will, therefore, be focusing on some of the most fundamental practices of successful DGNSS surveying.

Pre-survey Preparations

Ensure all your equipment is properly calibrated, batteries are charged, and software and firmware updates are done before commencing the survey.

Check the weather forecast and satellite availability and any other factors that might cause interference or obstruction to the measurement, including buildings, trees, power lines, or radio signals. Also, prepare for any contingencies related to the malfunction of equipment, loss of data, and denial of access to the site of interest.
Locate memory devices (typically SD cards) and verify sufficient storage is available.
If not familiar with the gear, perform a full setup test, check that the communications are working correctly between devices before heading to the field, or be prepared to troubleshoot later.
If possible, investigate your field area. Topographic maps, Google Earth Imagery, or pre-trip to the area can dramatically increase your chances of success on your field day. Using this knowledge, plan the base sites, data points and paths to navigate the field site. A good plan will reduce time spent in the field later. Anticipate the number of points to be collected and time associated with the plan.
Pack all equipment using a checklist.

In-Field Techniques

Stable and High Ground: Place the base station on stable, solid ground to ensure that it will stay in one place during the entire survey. Put the base station as high as practical. This minimizes multipath from the surrounding area and enables the radio broadcast to the maximum distance. Also, the higher the gain on the antenna, the longer the range.
Clear Sky View: Mount the base GPS antenna where there will be clear view of the sky in all directions. Not near vertical obstructions like buildings, deep cuttings, site vehicles, towers, tree canopy, etc. This is to ensure that the receiver do not have to deal with messy multi-path signals.
Check Base Station Regularly: Periodically check the base station to make sure it is functioning correctly and is transmitting data. Ensure that the base is monitored at all time as it can be stolen or knocked down by wind/animals.
Field Notes: Keeping detailed field notes of the survey, including possible problems or oddities observed in the course of surveying.
Data Quality Checks: Checking the quality of correction data received from time to time and verifying the positional accuracy obtained from the Rover that should be within the acceptable limits.
Safety Precautions: Observe precautions for personal safety, especially when working in the vicinity of live traffic, in remote areas, or in bad weather.
Known Coordinates: Use a location with known and accurate coordinates or establish the position of the base station by precise static observations.
Power Source: The GNSS receiver should never run out of power. The GNSS receiver has an internal battery that must be charged. Provide external power in order to use continuously for more than a day without losing power at the base station.
Electromagnetic Interference: Ensure that the base is away from heavy machinery, radio/mobile towers and overhead power lines as the electromagnetic fields associated with these utilities can interfere with the DGNSS signals.

Data Collection Techniques

Effective Effective data collection in a DGNSS survey involves various techniques to ensure precision and reliability. Here are key techniques for data collection during a DGNSS survey:data collection in a DGNSS survey involves various techniques to ensure precision and reliability. Here are key techniques for data collection during a DGNSS survey:

Static Positioning
Static positioning is a method in DGNSS (Differential Global Navigation Satellite System) surveys that involves collecting data at a fixed point over an extended period to achieve high-precision coordinates. This technique is particularly useful for establishing control points, base station locations, and other critical survey markers that require high accuracy.

Rapid Static (Fast Static)

Rapid static positioning, also known as fast static positioning, is a technique in DGNSS (Differential Global Navigation Satellite System) surveys that balances the accuracy of static positioning with the efficiency of kinematic methods. It involves shorter observation times than traditional static surveys, making it suitable for projects requiring quick and precise measurements at multiple points.

Real-Time Kinematic (RTK) Surveying
Real-Time Kinematic (RTK) is a high-precision positioning technique used in DGNSS (Differential Global Navigation Satellite System) surveys. RTK provides real-time corrections to the rover receiver, enabling centimeter-level accuracy. This technique is widely used in applications requiring immediate and precise positioning, such as construction, agriculture, and topographic surveys.

Post-Processed Kinematic (PPK)
Post-Processed Kinematic (PPK) is a technique in DGNSS (Differential Global Navigation Satellite System) that provides high-precision positioning by applying differential corrections after data collection. Unlike Real-Time Kinematic (RTK), PPK does not require real-time communication between the base and rover, making it suitable for areas with poor communication infrastructure.

Adhering to best practices in DGNSS surveying is essential for achieving high-precision and reliable results. By meticulously setting up your base and rover stations, continuously monitoring signal quality, and carefully documenting field conditions, you can mitigate potential sources of error. Utilizing techniques like RTK, PPK, static, and rapid static positioning, each suited for specific scenarios, allows for flexibility and precision in various surveying contexts.

This brings us to the end of the blog. I hope this article gained some knowledge for you!

Thank you for reading.

About SurveyGyaan

Surveypod: www.surveypod.in (DGNSS Manufacturer Website)

Surveyaan: www.surveyaan.com (Drone Manufacturer Website)

Surveyaan Geoworkspace: app.surveyaan.com (Cloud Photogrammetry Software Website)

How many Satellites and Channels require in your DGNSS?

Thu, 10 Apr 2025 06:28:45 +0000

In the realm of precision navigation and positioning, Differential GNSS (DGNSS) often emerges as a critical yet misunderstood technology. Despite its pivotal role in enhancing GPS accuracy, several myths persist, clouding its true value. Today, let’s discuss some common misconception in the survey world related to DGNSS (or DGPS).

You may have heard people emphasize the importance of having 400, 800, or even 1200 channels in a DGNSS receiver. Have you ever thought deeper to understand what this actually means? Let’s clarify this with some simple mathematical calculations.

There are a total of 120 operational satellites: GPS (31), Galileo (24), GLONASS (24), BeiDou (30), NavIC (7), and QZSS (4). These satellites are distributed across the orbital plane and are not all visible from a particular point on Earth.

What is an Elevation Mask?

An elevation mask is a threshold angle that defines the minimum elevation above the horizon that a satellite must have to be considered in the positioning calculations of a DGNSS receiver. The purpose of this mask is to filter out low-angle satellite signals that are more likely to be degraded by atmospheric interference, multipath effects, and obstructions.

What value to keep for Elevation Mask?

It is recommended to set the Elevation Mask to 15 degrees to use only high-quality satellites for positioning. However, even with an Elevation Mask set to 5 degrees, you wouldn’t be able to see even half of the satellites simultaneously.

How many satellites with Elevation Mask as 5 degrees?

With an Elevation Mask of 5 degrees, you would only be able to track a maximum of 14 GPS, 6 Galileo, 6 GLONASS, 11 BeiDou, and 4 QZSS satellites. Out of the 7 NavIC satellites, only 5 are operational, and many companies do not support NavIC.

So how many Channels?

Now, let’s talk about channels. The L1 and L2 bands require only one channel each, whereas the L5 band requires two channels. Interestingly, out of the 120 satellites, only 40–45 have L5 bands.

Here’s the mathematical calculation with a 5-degree Elevation Mask (in general, if you set it to 15 degrees, which is the industry standard, the number would be lower):

Total satellites being used: 14 (GPS) + 6 (Galileo) + 6 (GLONASS) + 11 (BeiDou) + 4 (QZSS) + 5 (NavIC) = 46 satellites. Not all of these would have L5 bands; let’s assume 20 do.

So, the total number of channels required would be: 46*1 (L1) + 46*1 (L2) + 20*2 (L5) = 132 channels. In reality, this is still an exaggerated number. In the real world, no more than 100 channels are typically required. Claims of needing 400, 800, or even 1200 channels are overly futuristic and marketing/selling strategy. It will take more than 10–15 years to even approach the utilization of 300 channels.

Does All Satellites Used in DGNSS Provide the Same Level of Accuracy?

The accuracy of signals from GNSS satellites can vary due to several factors, including the satellite’s position, health, and atmospheric conditions affecting the signal’s travel to Earth. Differential GNSS (DGNSS) enhances overall accuracy by correcting these variable errors. However, the effectiveness of DGNSS corrections is influenced by the quality of the correction data, which depends on the proximity and condition of the reference station, as well as the quality of the communication link between the reference station and the DGNSS receiver. Therefore, it is crucial to closely examine the quality of the satellites being used for positioning.

Thank you for reading.

About SurveyGyaan

Surveypod: www.surveypod.in (DGNSS Manufacturer Website)

Surveyaan: www.surveyaan.com (Drone Manufacturer Website)

Surveyaan Geoworkspace: app.surveyaan.com (Cloud Photogrammetry Software Website)

DGNSS Series-Errors in GNSS

Wed, 10 Jan 2024 06:30:46 +0000

Global Navigation Satellite Systems (GNSS) such as GPS, GLONASS, and Galileo are critical in providing accurate location information for a variety of applications ranging from navigation and surveying to agricultural and emergency services. However, the precision of GNSS positioning is susceptible to a variety of faults that can jeopardize the dependability of location data. In this blog article, we will look at various forms of GNSS errors and how they affect accuracy.

These are the factors that may make it difficult for a GNSS receiver to calculate an exact position and degrade precision.

Satellite Clock Errors

GNSS satellites are equipped with atomic clocks to provide precise timing signals.

However, variations in the satellite clocks can introduce errors in the ranging measurements, affecting the accuracy of position calculations. Different global systems use different types of atomic clocks, and most satellites will have multiple types of clocks on board. For e.g. Rubidium and Caesium are standard on GPS , Galileo has Hydrogen maser and Rubidium.

These clocks are incredibly accurate, but they aren’t perfect, and experience ‘drift’. This means they lose or gain one nanosecond for every three hours of time.

For example, 10 nanoseconds of clock error results in 3 meters of position error.

The figure above depicts the satellite clocks present in GALILEO GNSS

Orbit errors

GNSS satellites travel in very precise, well-known orbits. However, like the satellite clock, the orbits do vary a small amount. Also, like the satellite clocks, a small variation in the orbit results in a significant error in the position calculated.

Orbital errors occur when the GNSS satellite is not exactly in the position that was predicted and transmitted through orbit data. Some GNSS surveying techniques require the final ephemerides to be used to guarantee the best solution for a position.

This error source can be reduced by means of relative measurement, or by post-processing when observed and post-processed orbit data of good quality are available.

Ionospheric Delay

The ionosphere is the layer of atmosphere between 50 and 1,000 km above the Earth. This layer contains electrically charged particles called ions due to solar radiation. These ions alter the transmission time of the satellite signals and can cause a significant amount of satellite position error (typically ±5 meters). Modelling the ionosphere is highly variable and more difficult to model. This is generally the largest error source in GNSS measurement, but it can be reduced by using relative or multi-frequency measurement.

Tropospheric Delay

The troposphere is the layer of atmosphere closest to the surface of the Earth. It is approximately 8 and 14 km deep, depending on the location on the Earth’s surface. Tropospheric errors are caused by temperature, density, pressure or humidity changes.. Here, the GNSS signal is mainly affected by water vapour, which varies is a lot in time and space.

Multipath

Multipath error occurs when a signal from the same satellite reaches a GNSS antenna via two or more paths, such as reflected off the wall of a building. The reflected signal clearly has to travel further to reach the antenna and so it arrives with a slight delay. In an environment with tall houses or trees, multipath errors are more common. This error source can be partially reduced by observing over a longer period and with good quality GNSS equipment. Also, to reduce multipath errors place the GNSS antenna in a location that is away from the reflective surface.

Receiver Noise

Receiver noise refers to the position error caused by the GNSS receiver hardware and software. All GNSS receivers are subject to other radio waves that occur naturally or through other processes. These other radio waves, along with other types of electrical interference are what is known as background noise, and impact the ability of the receiver to ‘hear’ the GNSS signals. High-end GNSS receivers tend to have less receiver noise than lower-cost GNSS receivers. Calibration and signal processing techniques are employed to minimize these errors, but they can still impact accuracy.

Impact on Accuracy

Positional Inaccuracy: Cumulative effects of the mentioned errors can lead to significant inaccuracies in the calculated position. This is particularly critical in applications where precise positioning is essential, such as in aviation, surveying, and autonomous vehicles.
Time-to-First-Fix: Errors can also impact the time it takes for a GNSS receiver to acquire the first fix. In scenarios where rapid and accurate positioning is crucial, delays in acquiring a fix can have serious consequences.
Navigational Integrity: In safety-critical applications, like aviation, GNSS errors can compromise the navigational integrity of the system. This is why redundancy and augmentation systems are often used to enhance accuracy and reliability.
Increased Uncertainty: Users relying on GNSS for navigation or surveying may experience increased uncertainty in their results. This uncertainty can be a limiting factor in applications where precision is paramount.

While GNSS has revolutionized navigation and positioning, understanding and mitigating errors are crucial for ensuring accuracy. Users should be aware of the various error sources and employ techniques such as differential corrections, augmentation systems and the use of multiple constellations to enhance GNSS performance