GNSS & Geodesy Hub – RTK, PPK, TPU & Projections
GNSS & Geodesy Hub
Your complete resource for modern GNSS positioning, RTK/PPK workflows, geodetic projections, and Total Propagated Uncertainty (TPU) calculations. Designed for hydrographic surveyors, geospatial engineers, and GIS professionals working in rivers, ports, and offshore environments.
Why This GNSS & Geodesy Hub?
Accurate positioning is the foundation of every hydrographic survey, geospatial project, and engineering design. From establishing precise horizontal and vertical control to processing complex geodetic transformations, GNSS technology is essential for modern surveying. This hub brings together every critical tool and guide you need — from Total Propagated Uncertainty (TPU) calculations compliant with IHO S‑44 standards to RTK/PPK positioning workflows, geodetic projections (UTM, LCC, etc.), and GNSS base station setup protocols.
All tools and guides are based on field-tested procedures developed over 25+ years of working on the Jamuna, Padma, and Meghna rivers. Every workflow is aligned with IHO S‑44 Special Order standards, ISO 17123 (GNSS uncertainty), and BIWTA tidal datums for local water level reductions.
Whether you are a junior surveyor learning the basics of GNSS positioning for the first time, or a senior geospatial engineer preparing a detailed uncertainty budget for a client submission, this hub has everything you need to produce high‑quality, defensible geodetic deliverables.
Uncertainty & Accuracy
RTK, PPK & Positioning
Projections & CRS
Water Level & Reflectometry
📐 Industry Standards & Compliance
All GNSS workflows follow IHO S‑44 Special Order (horizontal & vertical accuracy), ISO 17123 (GNSS uncertainty), NGS 58 (geodetic projections), and BIWTA tidal datums for water level reductions.
Frequently Asked Questions
What is Total Propagated Uncertainty (TPU)?
TPU is the combined effect of all error sources in hydrographic surveying – including GNSS, tide, and sensors – calculated as the square root of the sum of squares of horizontal and vertical errors. It is used for IHO S‑44 compliance and quality assurance.
What is the difference between RTK and PPK?
RTK (Real-Time Kinematic) provides centimeter-level positioning in real-time using a base station and a rover. PPK (Post-Processed Kinematic) records raw data and processes it after the survey, which can be more reliable in areas with poor communication links.
What is a geodetic projection?
A geodetic projection is a mathematical transformation that converts the 3D curved surface of the Earth (latitude/longitude) into a 2D flat map (Easting/Northing). Common projections include UTM, LCC, and Mercator.
How do I set up a GNSS base station?
Base station setup involves selecting a stable location with a clear sky view, setting up the receiver, and performing a site calibration to determine the local coordinate transformation. Our GNSS Base Station Setup Guide provides a step-by-step protocol.
What is IHO S‑44 Special Order?
IHO S‑44 Special Order is the highest accuracy standard for hydrographic surveys, requiring horizontal uncertainty ≤ 2 m at 95% confidence and vertical uncertainty ≤ 0.25 m at 95% confidence.
How accurate are these tools for field use?
Yes — all formulas are verified against standard engineering references and calibrated with field data from major rivers including Jamuna, Padma, and Meghna. However, always cross-check critical results with site-specific measurements.
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