There are chiefly two types or senses of topography, and one is more prevalent in the United States and the other in Europe. In the U.S., the large-scale study of topographic maps filled with elevation contours has made the term "topography" a synonym to the word "relief." In Europe, the term "topography" is more concerned with the study of a place, such as the local history and culture along with the man-made and vegetative features.
Irrespective of the fields of use, topography is applied for determining the exact position of any geographical or biological feature and its parts in respect to a reference point or simply in space. The units used for this determination are the horizontal coordinate system (longitude and latitude) and altitude. To make things clearer, different naming conventions are used in different fields that are also a part of topography.
The different objectives of topography vary according to the field in which it is applied. Detailed topographical information of a particular land is important for planning construction jobs, civil engineering, reclamation works and public works. It is also essential to minutely survey a terrain for initiating any military incursions or some geological explorations. It is used by a surgeon to explore the malfunctioning part of an organ before starting surgery and to search to cancerous cells before beginning radiation therapy.
The approaches to studying topography also vary according to the size or scale and accessibility of the feature under study. Direct survey involves the gathering of topographical data through manual procedures and the use of some leveling instruments like dumpy levels, theodolites and clinometers (a tool that measures elevation angles and slope). Remote sensing is also a method of collecting geographical data--but from a distance. Aerial and satellite imagery is another method of collecting topographical data that makes use of satellites and aerial surveys. Some other methods include photogrammetry and radar or sonar.
Many different models of topographic data exist, and each has its own significance. The most basic model of topographic data is the raw survey data that is highly dependent upon the analytical ability of the surveyors. In environmental science, the topographical data is represented in the grid mathematical model, also called raster images. In civil engineering, the data for a land surface is modeled on triangulated irregular network (TIN) models. Remote sensing data contributes a large portion of any topographical data, but it also contains the most inconsistencies and errors, which need to be sorted out before its application.