Understanding Land Topography: Surveys, Definitions & Features

1) Topography

The set of principles and procedures to represent a land surface, including natural and artificial shapes and details.

a) Planimetry

Focuses on the projection of the field on a horizontal plane.

b) Altimetry

Measures level differences in points of the terrain.

Planimetry and Altimetry: Together, they allow for the creation of a topographical map, showing both position and elevation of land points.

2) Forms and Definitions of Land

a) Geoid

The gravitational equipotential surface closest to the average sea level.

b) Ellipsoid

A mathematical model of the Earth formed by rotating an ellipse about its minor axis.

c) Geographical Features

• CENID: An imaginary point at the intersection of all planes perpendicular to the ground.
• Nadir: The point diametrically opposite the zenith.
• Geographical Coordinates: Height and length.
• Meridian: A straight line intersecting the horizontal meridian plane of a point on the surface, marked northeast-south.
• Vertical Line: A line passing through a point on the Earth's surface and the center of the Earth.

3) Topographic Survey and Stakeout

3.1) Survey

Operations to determine horizontal and vertical distances and angles, used to create a plan.

3.1.1) Geodetic Surveys

Surveys of large areas with high precision, where each point is determined by its longitude and latitude.

3.1.2) Topographic Maps

Surveys of small land tracts, considering the Earth as flat, where each point is determined by its height or elevation.

3.2) Field Operations

• Recognition of the field to gather site information.
• Decision on the method of surveying.
• Determination of the vertices of a polygonal base.
• Making measurements.
• Data recording and measurement in appropriate books.

3.4) Surveying Classes

• a) General Survey: Used to locate boundaries, property lines, measure and divide areas, and locate land in general flat areas.
• b) Longitudinal Survey: Used to survey or build transport routes, canals, aqueducts, etc.
• c) Hydrographic Survey: Used to obtain ground water levels, coastal lines, or coastal and mountainous terrain of lakes and rivers.
• d) Urban Cadastral Survey: Surveys made in cities, urban areas, and municipalities.

Topographical Stakeout: An inverse operation to the survey, where the position of certain details is indicated to guide construction work.