GELE Geodesy — Satellite Geodesy and GNSSConcept Map

Concept

GNSS Positioning Principle

Sub Concepts

• Trilateration
• Satellite Geometry
• Receiver Position (X, Y, Z)
• Receiver Clock Bias (Δt)
• Minimum 4 Satellites Required

Relationship To Central

Foundational method underlying all GNSS operations

Concept

GNSS Observables

Sub Concepts

• Pseudorange (ρ = c·Δt)
• Carrier Phase
• Integer Ambiguity Resolution
• Measurement Accuracy Levels
• Metre-Level vs Millimetre-Level Precision

Relationship To Central

Raw measurements that enable positioning

Concept

Error Sources and DOP

Sub Concepts

• Satellite Clock Errors
• Orbital Errors
• Ionospheric Delay
• Tropospheric Delay
• Multipath
• Receiver Noise
• Dilution of Precision (DOP)
• PDOP, HDOP, VDOP, GDOP

Relationship To Central

Factors that limit positioning accuracy

Concept

Differential and RTK Methods

Sub Concepts

• DGPS (Differential GPS)
• Static Differential
• Base Station Corrections
• RTK (Real-Time Kinematic)
• Carrier-Phase Differential
• cm-Level Accuracy
• Real-Time Processing

Relationship To Central

Techniques for improving positioning accuracy

Concept

Reference Frames and Datums

Sub Concepts

• WGS84 Datum
• ITRF (International Terrestrial Reference Frame)
• PRS92 (Philippine Reference System)
• Frame Transformation
• Geocentric vs Local Datums
• Datum Conversion Requirements

Relationship To Central

Coordinate systems where GNSS positions are expressed

Concept

GNSS Constellations

Sub Concepts

• GPS (United States)
• GLONASS (Russia)
• Galileo (European Union)
• BeiDou (China)
• Regional Systems
• Constellation Geometry

Relationship To Central

Satellite systems providing global navigation signals

Concept

Practical Applications in Philippine Geodesy

Sub Concepts

• Control Densification
• Stake-Out Operations
• Land Survey Documentation
• Compliance with RA 4374 and RA 8560
• PRS92 Tie-In Requirements
• PPCS/UTM Zone Integration

Relationship To Central

Real-world implementation aligned with PRC standards

To

Trilateration

From

GNSS Positioning Principle

Strength

strong

Relationship

Geometric foundation: solving 4 equations from 4 satellites to find X, Y, Z, Δt

To

Pseudorange

From

GNSS Positioning Principle

Strength

strong

Relationship

Observable used to measure distance from each satellite

To

Carrier Phase

From

Pseudorange

Strength

strong

Relationship

Alternative observable with higher precision but requiring ambiguity resolution

To

Accuracy

From

Error Sources and DOP

Strength

strong

Relationship

DOP multiplies measurement error to determine final positioning accuracy

To

Dilution of Precision

From

Satellite Geometry

Strength

strong

Relationship

Well-spread satellites produce low DOP; clustered satellites produce high DOP

To

DGPS Corrections

From

Ionospheric Delay

Strength

moderate

Relationship

Differential methods remove common atmospheric delays at similar locations

To

RTK Real-Time Kinematic

From

Tropospheric Delay

Strength

moderate

Relationship

Carrier-phase RTK less sensitive to tropospheric effects than pseudorange

To

RTK Real-Time Kinematic

From

Carrier Phase

Strength

strong

Relationship

RTK relies on real-time carrier-phase differential measurements

To

Centimetre-Level Accuracy

From

RTK Real-Time Kinematic

Strength

strong

Relationship

RTK achieves cm-level positioning through rapid ambiguity resolution

To

PRS92 Datum

From

WGS84 Datum

Strength

strong

Relationship

GNSS operates in WGS84; results must be transformed to PRS92 for Philippine surveys

To

PPCS/UTM Projection

From

PRS92 Datum

Strength

strong

Relationship

PRS92 geodetic coordinates are projected to PPCS/UTM for practical survey work

To

Survey Documentation

From

PPCS/UTM Projection

Strength

strong

Relationship

Final survey coordinates reported in PPCS/UTM Grid system per RA 8560

To

Control Densification

From

Static DGPS

Strength

strong

Relationship

Static differential GPS used to establish new control points tied to known bases

To

Stake-Out

From

RTK Real-Time Kinematic

Strength

strong

Relationship

RTK enables real-time positioning for setting-out survey points on ground

To

Satellite Geometry

From

GNSS Constellations

Strength

moderate

Relationship

More constellations (GPS + GLONASS + Galileo) improve overall geometry and availability

To

RTK Accuracy

From

Multipath Error

Strength

moderate

Relationship

Multipath is a major error source limiting cm-level RTK accuracy in urban areas

To

Carrier Phase

From

Integer Ambiguity Resolution

Strength

strong

Relationship

Core challenge in carrier-phase processing: determining integer wavelength count

To

PRS92 Mandatory Use

From

PRC Licensure Standards

Strength

strong

Relationship

RA 8560 requires all Philippine surveys in PRS92; WGS84 is not acceptable

To

Monument Establishment

From

RA 4374 Standards

Strength

strong

Relationship

Legal requirement for proper marking and documentation of geodetic control points

To

NTRIP/Radio Communication

From

Real-Time Kinematic

Strength

moderate

Relationship

RTK requires real-time base station corrections via communication link

To

Fourth Satellite

From

Receiver Clock Bias

Strength

strong

Relationship

Clock bias is the fourth unknown requiring a fourth pseudorange equation

To

Receiver Clock Bias

From

Pseudorange Equation

Strength

strong

Relationship

Each pseudorange includes the receiver clock error Δt as unknown

To

Pre-Survey Planning

From

DOP Analysis

Strength

moderate

Relationship

Engineers check DOP forecasts to plan optimal survey window for best geometry

To

Error Propagation

From

Accuracy = DOP × σ

Strength

strong

Relationship

Fundamental equation relating geometry (DOP) to measurement precision (σ) and final accuracy

To

Common Error Removal

From

Base Station Corrections

Strength

strong

Relationship

DGPS base computes residual errors that are subtracted from rover measurements

To

WGS84 to PRS92 Conversion

From

7-Parameter Similarity Transform

Strength

strong

Relationship

Precise mathematical transformation accounting for translation, rotation, and scale

To

Ellipsoidal to Orthometric Height

From

Geoid Model

Strength

strong

Relationship

Geoid undulation N converts ellipsoidal height h to orthometric H per H = h - N

To

RA 8560 Compliance

From

Survey Quality Assurance

Strength

strong

Relationship

All surveys must meet RA 8560 accuracy and documentation standards before acceptance