3.4.8.6. Pseudo-kinematic surveying

Pseudo-kinematic GNSS surveying is similar to stop-and-go technique, and is a combination of both static and kinematic methods.

Pseudo-kinematic surveying blends two different methods: static and kinematic surveying. While it shares characteristics with kinematic surveying, it introduces a unique initialization process similar to the stop-and-go technique. This combination makes it an effective method in various surveying scenarios, particularly in environments filled with obstructions such as tall buildings or overhanging trees.

Think of pseudo-kinematic surveying like playing a game of hide and seek in a playground with obstacles. Imagine you need to find friends who might be hiding under slides or behind trees (obstructions). Instead of running around and searching blindly (kinematic), you pause at certain locations (stop-and-go) to get a better sense of where people might be hiding and then move, making the search more efficient.

This feature offers a more favourable positioning technique for the areas having obstructions to signals, such as bridge overpasses, tall buildings, and overhanging vegetation.

One major advantage of pseudo-kinematic surveying is its ability to operate effectively in areas where signals may be obstructed. Traditional kinematic methods require a clear line of sight to at least four satellites for accurate positioning. In contrast, pseudo-kinematic surveying tolerates the loss of satellite lock caused by excessive obstructions, allowing surveyors to work in environments previously challenging for GNSS.

Imagine navigating a city filled with skyscrapers using a GPS on your phone. If your GPS loses connection when your phone is near a tall building, you might struggle to find directions. Pseudo-kinematic surveying is like having a backup plan where, instead of panicking without GPS, you can still gather crucial information by pausing and triangulating your last known position while moving cautiously around the buildings.

Each point is occupied for 5-10 minutes for baselines up to 10 km or less. These points are revisited multiple times; may be after 1 hour but not more than 4 hours.

In pseudo-kinematic surveying, surveyors typically occupy each survey point for a duration of 5 to 10 minutes. This time allows for enough data collection to account for any minor discrepancies caused by the surrounding environment. Additionally, revisiting the same point multiple times within a timeframe of one to four hours helps improve accuracy by resolving ambiguities in the measurements.

Imagine you're taking a group photo with friends at a park. You set up the camera and take several shots, allowing different people to find the best angle and pose. By taking multiple photos from slightly different positions, you ensure that everyone looks great, and you can choose the best image later. Pseudo-kinematic surveying works similarly by repeatedly collecting data at a point to capture the most accurate position possible.

Multiple observations of same point with different times will resolve the integer ambiguity.

In surveying, integer ambiguity refers to the challenge of accurately determining the exact phase of satellite signals, which can affect the final position calculation. Pseudo-kinematic techniques help resolve these ambiguities through multiple observations of the same point over time. By comparing these different readings, surveyors can deduce the precise location, improving the overall data accuracy.

Consider trying to figure out the score of a game that was recorded on different cameras. If you only view one camera's footage, you might miss key moments that clarify the score. However, if you review highlights from various cameras, you'll have a clearer and more accurate picture. This is similar to how multiple observations in pseudo-kinematic surveying help clarify location ambiguity and improve accuracy for each point surveyed.

--