GELE Photogrammetry & Cartography — Scale, Relief Displacement and ParallaxConcept Map

Concept

Photographic Scale

Sub Concepts

• Representative Fraction (RF)
• Principal Scale (at datum level)
• Scale variation with terrain elevation
• Scale calculations from flying height and focal length

Relationship To Central

Foundation for understanding how image dimensions relate to ground reality; essential for interpreting displacement and parallax measurements

Concept

Relief Displacement

Sub Concepts

• Radial displacement direction
• Displacement formula: d = rh/H
• Principal point as displacement origin
• Height extraction: h = dH/r
• Maximum displacement at photo edges
• Zero displacement at principal point

Relationship To Central

Primary method for determining object heights from single vertical photos; caused by vertical separation from datum

Concept

Stereoscopic Parallax

Sub Concepts

• Absolute parallax (P)
• Parallax difference (Δp)
• Flight line measurement direction
• Height formula: h = HΔp/(P+Δp)
• Parallax bar measurements
• Stereo model orientation

Relationship To Central

Alternative height determination method using two overlapping photos; basis for stereoplotters and digital photogrammetry

Concept

Geometric Relationships

Sub Concepts

• Similar triangles principle
• Radial line geometry
• Central projection perspective
• Photo coordinate systems
• Flying height above datum

Relationship To Central

Mathematical foundation explaining why displacement and parallax occur; connects image geometry to 3D space

Concept

Practical Applications in Philippine Surveying

Sub Concepts

• Digital elevation model (DEM) generation
• Orthophoto production
• Land classification (CA 141)
• Building height verification
• Terrain profile determination

Relationship To Central

Real-world implementation in PRS92 datum and PPCS mapping; regulatory compliance under RA 4374 and RA 8560

Concept

Measurement Techniques

Sub Concepts

• Radial distance measurement (r)
• Displacement measurement (d)
• Parallax bar usage
• Micrometer measurement
• Digital coordinate extraction
• Image correlation methods

Relationship To Central

Practical methods for extracting numerical values from photos and stereo pairs

Concept

Error Sources and Limitations

Sub Concepts

• Flying height uncertainties
• Measurement precision limits
• Tilt and swing effects
• Atmospheric refraction
• Image resolution constraints

Relationship To Central

Critical understanding for quality assurance and interpretation of photogrammetric height data

To

Photographic Scale

From

Relief Displacement

Strength

strong

Relationship

Relief displacement magnitude depends on object height relative to scale; scale variation with elevation affects interpretation

To

Geometric Principles

From

Relief Displacement

Strength

strong

Relationship

Relief displacement is direct result of central projection geometry; similar triangles explain the mathematical relationship

To

Photographic Scale

From

Stereoscopic Parallax

Strength

moderate

Relationship

Parallax measurement scale depends on flying height and focal length; affects precision of height calculations

To

Geometric Principles

From

Stereoscopic Parallax

Strength

strong

Relationship

Parallax arises from baseline difference between two camera positions; 3D similar triangles explain height formula

To

Measurement Techniques

From

Relief Displacement

Strength

strong

Relationship

Accurate measurement of radial distance and displacement critical for height accuracy; requires careful photo analysis

To

Measurement Techniques

From

Stereoscopic Parallax

Strength

strong

Relationship

Parallax bar and digital correlation methods are primary tools; measurement precision directly affects height precision

To

Error Sources and Limitations

From

Relief Displacement

Strength

strong

Relationship

Flying height uncertainty, focal length error, and tilt distortion directly propagate to height error via formula

To

Error Sources and Limitations

From

Stereoscopic Parallax

Strength

strong

Relationship

Absolute parallax measurement error and atmospheric refraction affect stereo height accuracy; baseline uncertainty critical

To

Philippine Applications

From

Relief Displacement

Strength

moderate

Relationship

Used for rapid building height verification and DEM generation for CA 141 land classification under PRS92 datum

To

Philippine Applications

From

Stereoscopic Parallax

Strength

strong

Relationship

Primary method for generating digital elevation models and orthophotos referenced to PRS92; basis for modern mapping under RA 4374

To

Geometric Principles

From

Photographic Scale

Strength

moderate

Relationship

Scale is inverse of flying height in perspective geometry; both scale and geometry relate image distance to ground distance

To

Measurement Techniques

From

Geometric Principles

Strength

moderate

Relationship

Understanding perspective geometry guides proper measurement methodology and explains why certain techniques work