Remote sensing Topography

1 remote sensing

1.1 passive sensor methodologies
1.2 photogrammetry
1.3 active sensor methodologies

remote sensing

remote sensing general term geodata collection @ distance subject area.

passive sensor methodologies

besides role in photogrammetry, aerial , satellite imagery can used identify , delineate terrain features , more general land-cover features. have become more , more part of geovisualization, whether maps or gis systems. false-color , non-visible spectra imaging can determine lie of land delineating vegetation , other land-use information more clearly. images can in visible colours , in other spectrum

photogrammetry

photogrammetry measurement technique co-ordinates of points in 3d of object determined measurements made in 2 photographic images (or more) taken starting different positions, different passes of aerial photography flight. in technique, common points identified on each image. line of sight (or ray) can built camera location point on object. intersection of rays (triangulation) determines relative three-dimensional position of point. known control points can used give these relative positions absolute values. more sophisticated algorithms can exploit other information on scene known priori (for example, symmetries in cases allowing rebuilding of three-dimensional co-ordinates starting 1 position of camera).

active sensor methodologies

satellite radar mapping 1 of major techniques of generating digital elevation models (see below). similar techniques applied in bathymetric surveys using sonar determine terrain of ocean floor. in recent years, lidar (light detection , ranging), remote sensing technique uses laser instead of radio waves, has increasingly been employed complex mapping needs such charting canopies , monitoring glaciers.