GELE Geodesy — Geodetic Control NetworksConcept Map

Concept

Horizontal Control

Sub Concepts

• Triangulation (angle measurement + baseline)
• Trilateration (EDM distance measurement)
• Traverse (connected lines with directions)
• GNSS Networks (geocentric positioning)

Relationship To Central

Methods for establishing X, Y (easting, northing) coordinates of control points

Concept

Vertical Control

Sub Concepts

• Precise Differential Leveling
• Trigonometric Leveling
• Benchmark establishment and adjustment

Relationship To Central

Methods for establishing Z (elevation) of control points

Concept

Orders of Accuracy

Sub Concepts

• 1st Order (highest precision)
• 2nd Order (intermediate)
• 3rd Order (survey-grade)
• Misclosure tolerance formulas
• Hierarchical densification principle

Relationship To Central

Classification system defining precision standards and misclosure tolerances

Concept

Triangulation Computation

Sub Concepts

• Law of Sines
• Baseline measurement and standardization
• Angle measurement and adjustment
• Triangle strength of figure (well-conditioned angles)

Relationship To Central

Mathematical framework for deriving unknown sides from measured angles and baseline

Concept

Quality Control & Standards

Sub Concepts

• RA 4374 (Geodetic Engineer Law)
• RA 8560 (amendments to RA 4374)
• PD 1529 (Philippine Coordinate System)
• CA 141 (geodetic control standards)
• WGS84 and PRS92 reference frames
• PPCS and UTM projections

Relationship To Central

Ensures control networks meet Philippine and international specifications

To

Law of Sines

From

Triangulation

Strength

strong

Relationship

Triangulation uses Law of Sines to compute unknown sides from known baseline and measured angles

To

Triangulation

From

Baseline Measurement

Strength

strong

Relationship

Baseline is the primary measured distance in triangulation; all other sides derive from it via Law of Sines

To

Angle Measurement Error

From

Strength of Figure

Strength

strong

Relationship

Weak figures (small angles) amplify angular errors into large side-length errors; well-conditioned triangles minimize error propagation

To

Trilateration

From

Triangulation

Strength

moderate

Relationship

Both are horizontal control methods; triangulation measures angles, trilateration measures distances directly with EDM

To

2nd Order Control

From

1st Order Control

Strength

strong

Relationship

1st order provides the national framework from which 2nd order control is densified downward

To

3rd Order Control

From

2nd Order Control

Strength

strong

Relationship

2nd order provides regional control that is further densified into 3rd order local networks

To

Orders of Accuracy

From

Misclosure Tolerance

Strength

strong

Relationship

Each order has specific misclosure tolerance limits; 1st order tightest, 3rd order relaxed

To

Vertical Control

From

Leveling Tolerance

Strength

strong

Relationship

Tolerance formula T = k√K governs acceptable misclosure in leveling loops for each order

To

Benchmark Adjustment

From

Differential Leveling

Strength

strong

Relationship

Leveling loop misclosure is distributed proportionally to distance to adjust final benchmark elevations

To

PRS92

From

WGS84

Strength

strong

Relationship

WGS84 is the global reference frame; PRS92 is the Philippine-specific datum based on it

To

Philippine Coordinate System

From

PD 1529

Strength

strong

Relationship

PD 1529 defines the Philippine Coordinate System, the official reference for all geodetic control in the Philippines

To

UTM

From

PPCS

Strength

moderate

Relationship

Both are map projections; PPCS is Philippines-specific, UTM is international; control networks are tied to both

To

Geodetic Control Standards

From

RA 4374

Strength

strong

Relationship

RA 4374 (Geodetic Engineer Law) and RA 8560 amendments establish professional and regulatory framework for control networks

To

Vertical Control

From

Horizontal Control

Strength

strong

Relationship

Together they establish complete 3D control framework; horizontal gives X, Y; vertical gives Z

To

Triangulation

From

GNSS Networks

Strength

moderate

Relationship

GNSS is modern primary method; triangulation is classical but still used for densification and verification in Philippines

To

Triangulation Side Computation

From

Angle Measurement

Strength

strong

Relationship

Measured angles feed into Law of Sines to compute unknown triangle sides

To

Triangulation Adjustment

From

Triangle Angle Sum

Strength

strong

Relationship

Angle sum must equal 180° before applying Law of Sines; misclosure must be distributed among angles

To

Order Hierarchy

From

Control Network Densification

Strength

strong

Relationship

Densification always works downward from whole (1st order) to part (3rd order), never reversed

To

Control Network

From

Project Survey

Strength

strong

Relationship

All project surveys are tied to established control networks; control provides reference framework

To

Differential Leveling

From

Trigonometric Leveling

Strength

moderate

Relationship

Both establish vertical control; trigonometric is faster but less precise for rough terrain; differential is primary method