Essential Geospatial and Mapping Concepts

Understanding Geospatial Concepts

Geographical Coordinates

The geographic coordinate system determines all positions on the Earth's surface using two angular coordinates of a spherical coordinate system, which is aligned with the Earth's axis of rotation. It defines two angles measured from the center of the Earth:

• Latitude: Measures the angle between any point and the Equator. Lines of latitude are called parallels and are circles parallel to the Earth's surface.
• Longitude: Measures the angle along the Equator from anywhere on Earth. In most modern societies, Greenwich, London, is accepted as the 0° longitude. Lines of longitude are great circles passing through the poles and are called meridians.

Aerial Photography (Photogrammetry)

Photogrammetry is the science or art whose objective is to determine the dimensions and position of objects in space. This is achieved through measurements derived from the intersection of two or more photographs, or from a photograph combined with a digital terrain model for the represented area, which must have been previously created through the intersection of two or more photographs. Photogrammetry can be terrestrial or aerial, depending on where the images are obtained.

Relief (Topography)

Topography is the science that studies the principles and procedures for the graphic representation of the Earth's surface, including its natural and artificial forms and details. Topographic maps use a system of dimensioned drawings, showing elevation using lines connecting points of the same level relative to a reference plane, known as contour lines.

Meridian

An imaginary semicircle, a 180-degree arc, which connects points of equal longitude and whose ends coincide with the North and South Poles of the Earth. The Prime Meridian is the Meridian of Greenwich, or 0°.

Parallel

An imaginary full circle parallel to the geographic Equator, which connects points of equal latitude.

Latitude

The angular distance, between 0° and 90°, from a point to the Equator.

Longitude

The angular distance between a point and the Greenwich Meridian.

Map

A scaled representation of reality, based on the use of a series of symbols, drawings, or colors that convey the status, distribution, and relationships between various phenomena.

Remote Sensing

A technique that obtains information about the Earth's surface by analyzing data acquired by a remote sensor or device, based on measurements of reflected or emitted electromagnetic energy.

Geographic Information System (GIS)

A GIS is a computerized system capable of storing, analyzing, and processing descriptive data of a land surface. Typically used for managing maps, represented within the system as one or more layers. Each layer contains geographic information (position of elements on Earth), topological information (relationships between elements), and thematic information (the specific theme or content being represented) on a particular aspect.