Simple geodetic measurements on buildings carry out levels, theodolites, steel measured tapes, roulettes.
The Level - the geodetic device for definition of relative height of points or horizon carrying over on demanded objects. The basic parts of a level - a telescope and cylindrical level or the jack with which help vizirnaja the telescope axis is resulted in horizontal position.
Urovnevye (fig. 109) establish levels N on a support - a tripod with a basic platform. The level telescope represents the optical system placed in the metal case (pipe) 5. From one edge of a pipe there is an objective 4, from another - an eyepiece 6. the line connecting the optical centre of an objective and perekrestie of a grid of threads, is called vizirnoj as a pipe axis. It direct at an observable subject. Rotation of a focus ring achieve the accurate image of an observable subject. Rotating okuljarnoe a ring, focus the image of a grid of threads.
a Fig. 109. A level :
1 - the elevating screw, 2 - a support, 3 - the fixing screw, 4 - an objective, 5 - a pipe, 6 - an eyepiece, 7 - level
In levels use levels cylindrical and round.
Cylindrical level 7 represents the glass ampoule filled with a liquid (spirit, an aether). The part of space with steams of this liquid is called as a level vial. The internal top surface of an ampoule is ground on an arch of certain radius. On the top its external surface two-millimetric divisions are put. The average point of a scale 0 is called nulpunktom. The level vial always aspires to occupy the highest position. It occurs only when vizirnaja the level axis is in horizontal position. Therefore readout spend only at position of a vial of level in nulpunkte.
Round level differs from cylindrical level that its ampoule is ground on a spherical surface. Divisions into an outer side represent concentric circles, and a level axis is the radius of the sphere passing through zero-point. This level serves for preliminary installation of levels into position.
The Theodolite (fig. 110) - the optical device for measurement or reception in nature of horizontal and vertical corners.
a Fig. 110. A theodolite :
1 - the elevating screw, 2 - a theodolite support, 3 - a horizontal circle, 4 - level, 5 - a pipe support, 6 - an eyepiece, 7 - a vertical circle, 8 - a pipe, 9 - an objective, 10 - fixing screws
The Basis of the theodolite established on a support, the support 2 with three elevating screws 1 serves. in supports 5 the pipe 8, having an eyepiece 6 and an objective 9 is fixed. A theodolite
Establish on trenozhnom a support, its vertical axis by means of level 4 result in steep (working), position, align over a point and on horizontal 3 and to vertical 7 circles measure accordingly horizontal and vertical corners. For measurement of a horizontal corner a pipe direct at a point which had to the left of the observer. Over a point vertically establish a mark - a round wooden stick with painted in red and white colours strips. On otschetnomu to the adaptation - limbu a horizontal circle - sight. Then translate a pipe on the second right point and again sight. The difference of readout also is a corner measured between points.
a Fig. 111. Geodetic devices and tools :
- nivelirnye rejki, - a roulette;
1 - centimetric divisions, 2,3 - razgrafka the black and red party, 4 - rejka in gathering, 5 - a roulette cloth, 6 - a drum for tape taking - up, 7 - a plug, 8 - the handle
Nivelirnye rejki, sliding (fig. 111, and folding; represent a wooden bar dvutavrovogo sections in width 10... 12 and thickness 2... 3см. From two parties rejki are put shashechnye centimetric divisions: 1 on one party, black 2 on a white background, on another - red 3. on the party with black divisions readout begins with zero from the basis (heel) rejki: figures mark decimeters. On the party with red divisions readout is conducted from any number depending on type rejki.
By means of levels and reek define heights of points or excess of one point over another. For this purpose a level establish into position. On points between which define excess, establish rejki. Reduction of a level and reek into position consists that vizirnuju result a pipe axis in horizontal position, and rejki establish vertically. Vertical position vizirnoj pipes is reached by means of levels, and vertical position reek measure by eye or by means of plumbs.
Metal roulettes (fig. 111, length 2; 5; 10 and 20м serve for measurement of small pieces, length 20; 30 and 50м - for breakdown of axes of buildings and constructions.
At marking works a metal roulette consistently postpone between initial and final points of a measured line. Watch, that the roulette tape did not deviate a straight line connecting these points. Usually lines measure two times-in direct and return directions; it gives the chance to find out gross blunders, to raise accuracy of measurements and to estimate their quality.