GELE Geodesy — Geodetic Datums and Coordinate SystemsConcept Map

Concept

Types of Datums

Sub Concepts

• Geocentric (Global) Datum
• Local (Regional) Datum

Relationship To Central

Datums are classified into two major categories based on their spatial coverage and ellipsoid positioning

Concept

Coordinate Systems

Sub Concepts

• Geodetic Coordinates
• Cartesian Coordinates
• Projected Coordinates

Relationship To Central

Multiple coordinate representations exist for expressing positions referenced to a datum

Concept

Philippine Datums

Sub Concepts

• PRS92 (Philippine Reference System 1992)
• Luzon Datum 1911
• Clarke 1866 Ellipsoid

Relationship To Central

Philippine geodetic work uses specific datums established by law and practice

Concept

Datum Transformation

Sub Concepts

• 3-Parameter Transformation
• 7-Parameter Transformation
• Helmert Transformation

Relationship To Central

Mathematical procedures to convert coordinates between different datums while maintaining accuracy

Concept

Reference Ellipsoids

Sub Concepts

• WGS84 Ellipsoid
• Clarke 1866 Ellipsoid
• ITRF Ellipsoid

Relationship To Central

The mathematical model used by each datum to represent Earth's shape

Concept

Datum Origin and Orientation

Sub Concepts

• Origin Station
• Azimuth Reference
• Height Datum

Relationship To Central

The specific positioning of the ellipsoid relative to the Earth distinguishes one datum from another

To

Reference Ellipsoid

From

Datum

Strength

strong

Relationship

Every datum is defined by a specific reference ellipsoid with fixed semi-major axis and flattening

To

Coordinate Systems

From

Datum

Strength

strong

Relationship

All coordinates must be referenced to a datum; coordinates on different datums represent different positions

To

GPS/GNSS

From

WGS84

Strength

strong

Relationship

WGS84 is the standard datum for all satellite positioning systems; all raw GPS data is in WGS84

To

Clarke 1866 Ellipsoid

From

PRS92

Strength

strong

Relationship

PRS92 is defined on the Clarke 1866 ellipsoid with origin at Balanacan; required for Philippine land surveys

To

Cartesian Coordinates

From

Geodetic Coordinates

Strength

strong

Relationship

Geodetic (phi, lambda, h) and Cartesian (X, Y, Z) are two representations of the same point; conversion requires ellipsoid parameters

To

Cartesian Coordinates

From

Projected Coordinates

Strength

moderate

Relationship

Projected grid coordinates (E, N) are derived from Cartesian coordinates through map projection formulas

To

3-Parameter Method

From

Datum Transformation

Strength

strong

Relationship

3-parameter transformation applies only translations; suitable for small areas with standard precision

To

7-Parameter Method

From

Datum Transformation

Strength

strong

Relationship

7-parameter adds rotations and scale to 3-parameter; required for high precision and large areas

To

Helmert Equations

From

WGS84 to PRS92 Transformation

Strength

strong

Relationship

The standard method for converting between WGS84 (GPS) and PRS92 (Philippine local) uses Helmert 3 or 7-parameter

To

PRS92 Datum

From

Philippine Law (RA 4374)

Strength

strong

Relationship

RA 4374 establishes the legal framework for Philippine national mapping; PRS92 is the official Philippine datum

To

PRS92 Coordinates

From

Land Registration

Strength

strong

Relationship

Property descriptions and cadastral records in the Philippines must use PRS92 coordinates per RA 8560 and CA 141

To

7-Parameter Transform

From

Scale Factor (ppm)

Strength

moderate

Relationship

Scale factor in parts per million is one of the three rotation parameters in 7-parameter transformation; affects all distances uniformly

To

Geodetic-Cartesian Conversion

From

Ellipsoid Parameters

Strength

strong

Relationship

Semi-major axis (a), semi-minor axis (b), and eccentricity (e) of the ellipsoid are essential for coordinate transformations

To

PRS92 Origin

From

Balanacan Station

Strength

strong

Relationship

Balanacan is the defined origin station for the local PRS92 and Luzon Datum systems; all Philippine measurements reference this point

To

PRS92 Datum

From

UTM/PPCS Projection

Strength

strong

Relationship

Philippine grid coordinates (PPCS) and Universal Transverse Mercator are projections of points defined on PRS92 datum

To

Ellipsoidal Height h

From

Height Datum

Strength

moderate

Relationship

Ellipsoidal height is measured from the reference ellipsoid surface; orthometric height requires a geoid model

To

Datum Transformation Required

From

GPS Integration

Strength

strong

Relationship

GPS provides WGS84 coordinates; Philippine control networks use PRS92; transformation is essential for integration

To

Global Coverage

From

Geocentric Datum

Strength

moderate

Relationship

Geocentric datums like WGS84 are centered on Earth's mass center; provide worldwide positioning consistency

To

Regional Optimization

From

Local Datum

Strength

moderate

Relationship

Local datums like PRS92 are fitted to a specific region; provide better fit than global datums for that area

To

7-Parameter Helmert

From

Rotation Matrix

Strength

moderate

Relationship

The rotation matrix with three rotation angles (omega, phi, kappa) is applied in 7-parameter transforms for precise alignment