Chapter 5 and 6

• when extensive triangulation system linear distances are reduced to equivalent sea-level lengths
• (R/R+h) is also termed as sea level reduction factor
• Earth is not a perfect horizontal plane but a curved surface
• h'= 0.0675K^2 where h' is the correction due to earth's curvature and refraction and K is the horizontal distance of transit to a point sighted
• Spherical Excess -dependent on area of triangle and latitudes of vertexes. [ e''= (area/R^2sin01")
• Topography- art or practice of graphic delineation in detail usually on maps or charts
• Topographic map - a two-dimensional representation of a three-dimensional land surface. shows both horizontal and vertical positions by using contours or variation in colours
• Contour - a line connecting points of equal elevation
• Spot Elevation - a point representing the elevation of a critical location
• Map scale - ratio representing the size if illustration or reproduction in relation to the actual size of the area being mapped
• Topographic Symbols - pertinent features in the area using several symbols
• Ridge - higher values are inside the bend
• Valley - lower values are inside the bend
• Topographic map are used in geographic land - use planning, mining and civil engineering projects, estimation of volume of earthworks.
• Intervisibility - visibility between two points