Title 117 Higher Surveying.pdf ✅

MSTC 117: Higher Surveying 1. Cartography and Photogrammetry A map is a pictural representation of a certain vicinity. Photogrammetry is used to obtain physical information with scaling to produce the images. The scale is the ratio of the linear dimensions of the actual location and its image. Cartography is the process of making maps. Planes are used when taking aerial photos. It flies at an altitude of h, and the image forms behind the camera at a focal distance f. For the scale, f image size = H actual size scale = image size actual size scale = f H 2. Topography Topographical maps are pictural representations of locations that indicate the elevation of each area. Contour lines are imaginary lines that show areas with equal elevation. Since no location has two elevations at the same time, then no contour lines should intersect. However, two contour lines can coincide on the edges of extreme vertical drops like cliffs or bridge abutments. The distance between two contour lines is the contour interval. When contour lines are close to each other, it means the location is on a steep slope. On the other hand, the slope is gentle when contour lines are far from each other. A closed contour indicates a summit or a depression. Elevation changes are shown using hachures or shading in older topographical maps. Color coding is used to show elevation in newer maps. Red is used in places with higher elevation, and blue is used in places with lower elevation.
3. Hydrographic Surveying When measuring angles and distances while overwater, regular transits and dumpy levels cannot be used because of the rocking of the ship. Instead, a sextant is used to measure angles in hydrographic surveying. Radars are used to measure distances. The first electronic device made for measuring distances is the tellurometer. 3.1. Volumes of Reservoirs Topographic maps can be used to determine the reservoir’s volume capacity. Areas inside contour lines can be used as the horizontal cross-sections of the reservoir. Both the end-area method and the Prismoidal formula (see MSTC 120: Earthworks) are used to compute the volume. The end-area method is V = h 2 (A0 +∑Ainner + Alast) The Prismoidal formula is V = h 3 (A0 + 4∑Aodd + 2∑Ainner + Alast) Topographic Map of Ha aii Source: utton Institute: Penn State niversity Region with gentle slopes Summits Region with steep slopes