The study of Basic Geomatics or Surveying lies only on measuring angles and distances to be able to come up with the area of parcels of land and the volume of soil to be excavated of filled on site. The first goal of determining the boundary lines and determining land areas will be discussed later on the more advanced topics of Basic Geomatics. The volume of earthwork will be a topic covered in Route surveying. These are the different categories of Geomatics that students need to understand in order to prepare for Highways and Railroads Engineering as well as Transportation Engineering.
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| courtesy of Opti-cal Survey Equipment |
Horizontal measurements will be basically using the measuring tape. Although ideally, it is easiest to measure distances in level ground. Oftentimes, terrain will require surveyors to use procedures to adapt to the situation. Uneven grounds will ask for “Breaking Tape” method where surveyors will be dividing the distance into segments and measuring each segment accordingly.
Using the tape, students are required to understand the corrections with using the tape. Needless to say, erroneous tape readings will be resulting to erroneous distances later on.
1. Correction due to incorrect tape length. This correction is due to manufacturing defect. Measuring tapes are manufactured either too long or too short from standard. Although this has minimal effect, having the tape used so many times in distances will accumulate to bigger deviation to the real measurement.
2. Correction due to slope. With the sloping terrain, it would be impossible to directly measure the horizontal distances between points. This correction uses the Pythagorean theorem, using the properties of triangles, to compute for the horizontal distance. However, in steeper slopes, the formula would add parameters from binomial expansion.
3. Correction due to temperature. Unless the tape used in surveying is made of metal, temperature is expected to affect the measuring procedure. This is from the basic physics principle that higher temperature tends to expand matter, and likewise, shrink matter in lower temperatures.
4. Correction due to tension. Either simply laying out the tape or plumbing it in, standard tension is required to set the standard measurement of the tape, avoiding folds, wrinkles, or creases, which can cause errors in the reading. When the force pulling the tape is short from the standard, then possibility of wrinkles along the tape is expected. Similarly, if the pull exceeds the standard, the material will be showing longer measurements of the standard units.
5. Correction due to sag. The major cause of error in taping but only present in plumbing in procedures. Sag will always shorten the tape from the standard reading.
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| courtesy of Draper 88600 STFG/SG Expert |
Other corrections such as correction due to wind and correction due to alignment complete the set of corrections although they have negligible effect on the reading.
Although studied separately, the errors will always come combined on site. As long as students understand the principles of how these corrections are used then it would be easy to differentiate on which errors occur on site.
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