![]() The bearing from 1 to 2 must be equal to the plotted Azimuth from 1 to 2.įirst, the bearing along the circumference of the protractor is marked on the tracing paper, then the protractor is removed and Point 1 is connected by a thin line with the mark of bearing. check to see whether the direction of plotting is equal to the direction of surveying. (b) Begin by drawing in the starting point (Point 1) of the zero line. This way you can determine the size of the tracing sheet needed and how to fix the northern direction in order to save paper.įIGURE 38 Tracing Paper and Pad for Cross Section Paper (a) Mark the total length of the open-ended polygon on the paper and estimate the average bearing of the whole line. 20 Plotting a Zero Line with Protractor and RulerĮquipment required: Field notebook with data, tracing paper and cross-section paper, protractor, ruler and scale, medium-hard and hard pencils and an eraser. A sheet of cross-section paper should also be used as a pad between the drawing board and the tracing paper so that the vertical lines indicate the magnetic North direction (0) and allow the plotter to adjust the protractor accurately at each point of the open-ended polygon. ![]() Transparent tracing paper of the best quality should be used and a sheet of the required size should be fixed to the drawing board. If a ruler with these scales is not available the required scale is calculated and dawn on the tracing paper. Normal working scales are 1:2 000 or 1:5 000. The zero line is plotted with protractor and ruler at the scale of the map. A printing electronic calculator is useful for this purpose so that checks for errors may be made quite easily. ![]() It is recommended that intermediate sums for all control points and check points of the map be noted. First, the distances recorded in the field notebook are added to obtain the total length. The zero line is the first drawing which is prepared for the detailed plan. A zero line with a constant grade can be easily and quickly drawn by means of this simple method.įIGURE 37 Drawing a Zero Line on a Contour Map with a Divider If the trial zero line does not hit the terminal contour point reset the divider and mark off a second trial line. To draw a zero line on a 1:50 000 map with a vertical contour interval of 40 m set the divider points 9.9 mm apart for a 9 percent grade and then, starting at a control point, successively mark off the distances d s as shown in Figure 34. The contour lines on large scale maps are generalized, more like form lines, and do not reflect all breaks in the topography, therefore, it is necessary to add 10 percent of d s to the measured distance up from 7 percent grade to obtain proper zero lines.ĭivider Opening for Maps with a scale of 1:50 000 and 40 m ContoursĮxample: v = 40 m, scale 1:50000. The following simple proportions are used to calculate the divider opening based upon the contour interval, the allowed grade and the map scale.įIGURE 36 Cross - section Between Two Contour Lines for Divider Setting Even on a topographic map with a small scale this method can be applied to obtain a rough idea as to whether a route can be found, taking into account the steepness of the terrain and the allowable grades. 7.2 DIVIDER SETTINGĪ divider setting method is used for plotting a zero line with the required gradient on a contour map. Most of these details (culverts, retaining walls, cattle grids, etc.) should be prepared in standard drawings. Road construction details at a scale of 1:25 or 1:50. This drawing can be substituted by a written profile. ![]() Standard cross-sections at a scale of 1:50. The plotted road line is adjusted to the situation on the map. Detailed plan at a scale of 1:2 000 up to 1:5000. On the copies the road is drawn in red, the forest area in green. The planned road is generally outlined in this section. Section of a topographic map at a scale of 1:25 000 or 1:50 000. The following drawings should be prepared for a forest road: Careful lettering is important and is done in ink using lettering sets so that detail will not be lost. Drawings can be copied in pencil as well as in ink. ![]() For mechanical road construction in steep terrain simpler drawings are sufficient.Īt present, tracing paper is used for all drawings, this being mainly in pre-cut sheets of a standard size. MAPPING, CALCULATIONS AND DRAWINGS (BY SEDLAK)ĬROSS SECTIONS AND DETERMINATION OF CUT VOLUMESįormerly a considerable amount of time was spent on drawings of road projects since the roads were manually constructed. ![]()
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