Understanding Cartographic Data: Datums, Projections, and Remote Sensing
Understanding Cartographic Data
Datum Mapping
Datum mapping, or cartographic data, serves as the benchmark for measuring coordinates within a specific land area. It’s important to note that this measurement isn’t extrapolated to the entire surface. Each datum comprises an ellipsoid and a fundamental point.
Time Zones and UTM Projections
Time zones are divided into 6° longitude sections. UTM (Universal Transverse Mercator) projections are used to minimize distortions in the projected areas. The Earth is divided into 60 zones according to the UTM projection.
Latitude
Latitude represents the angular distance between any point on the globe and the Equator, measured either north or south. It is measured in degrees, with the Equator at 0 degrees and the poles at 90 degrees.
Longitude
Longitude is the angle measured between the meridian of a specific point and the Greenwich meridian, using the Equator as a reference.
Elevation
Elevation refers to the vertical distance between a point on the land surface and the average sea level.
Orthogonal Projection
Orthogonal projection involves projecting rays perpendicular to the plane through parallel projection lines. The level remains homogeneous throughout the screening process, resulting in no distortion. The size is maintained around the level of screening, and stereoscopic vision is not possible.
Central or Conical Projection
In central or conical projection, all rays pass through a central projection point, creating a specific angle to the projection plane. Its characteristics vary based on the elevation scale and distance to the central point of screening. Distortion is variable and depends on the scale. Size and shape change according to height and location on the map, allowing for stereoscopic vision.
Radial Distortion
Radial distortion occurs when objects in an aerial photograph begin to show distortion relative to the central flash point, revealing both the bottom and top of the object.
Flight Line
A flight line consists of a series of aerial photographs taken in succession along an imaginary line. These flight lines are photographed with the intention of having a common area (overlap) between adjacent photos.
Stereoscopy
Stereoscopy is the ability, possessed by beings with binocular vision, to perceive objects in 3D. This is because there are two views of the same object, allowing one to appreciate its length, width, and depth.
Electromagnetic Spectrum
The electromagnetic spectrum is a range of electromagnetic waves propagating at the speed of light (300,000 km/s). These waves are divided into visible light, infrared, ultraviolet, X-rays, gamma rays, radio frequency, and microwave. Each wave differs in frequency and length.
Visible Light
Visible light is the portion of radiation that our eyes can perceive, ranging from 360 to 700 nanometers.
Predial Letters
Predial letters are printed or digital representations of the Earth’s shape or surface, showing natural features and man-made structures with their geographic locations (longitude and latitude).
Legend of Letters
The legend of letters is the attached symbolism that explains the different components of a letter from a given sector, detailing both artificial and natural elements.
Cartography
Cartography is the graphical representation of the spatial distribution of objects in the real world.
Remote Sensing
Remote sensing is the acquisition of information about an object without being in direct contact with it.
Teledetection
Teledetection is based on the principle that all objects emit or reflect electromagnetic signals, which sensors record from a certain distance.
GIS (Geographic Information System)
A GIS is an information system specializing in managing and analyzing geographic information. Geographic information is an abstraction or representation of reality. The most important function of a GIS is analysis, where available information is used to produce new information.