Level reference survey for class 1 level reference net

After the selection and installation of class 1 level reference points, wait for 3 months of sinking period, then the outside survey work may be started. The outside original survey data, through results check, system error correction, and loop close difference analysis, could not discover that the survey data have gross errors and mistakes, and confirm that the resulting data are correct and without mistake. Then, the calculation work for class 1 grade 1 level reference net¡¦s level reference survey for horizontal difference may be started. In Taiwan, there are 1,010 new class 1 level reference points. With the cooperation survey gravity measurement points and Keelung level reference original point, there are 1,020 points. These and the distance weighted method are used to carry out class 1 grade 1 level reference net minimum refine control net horizontal differences. (Fix point K999). Furthermore cooperation survey with the old level reference point 319 and forced to the new points, the horizontal difference results related statistic information are as follows:

  1. Initial test the errors in the weighted units: set at 1.4 (mm*sqrt (1km)).
  2. Weighted matrix P¡G use the inverse of the survey section distance as the "weighted value".
  3. Total observation and survey number: 1354.
  4. Total level reference points: 1339.
  5. Number of level reference points with known height: 1 (K999).
  6. Extra survey number: 16 (1354 - 1338).

  7. Post test the errors in the weighted units: set at 1.4 (mm*sqrt (1km)).
  8. >Error among points: the largest value is the O Lun Bee grade 1 level reference point (Q019) 11.6mm.
  9. Survey number correction: between -0.70mm ~ +0.51mm.
  10. Net shape reliability analysis:
(1) Most of the survey number corrections are within ¡Ó0.4mm. This means the good survey quality.
(2) Extra survey number (16) and average extra survey weight fraction (f0 = 0.372), means that although that the overall net shape is not closed arranged. It is controllable with good reliability.
(3) The overall internal reliability reference value is 6.557. This means that the survey number has gross differences. If the gross is greater than £_'0 times survey number, it may be detected.
(4) The overall outside reliability value is 5.196. This means that the maximum impact of the included gross error to the estimation of the unknown number is £_"0 times survey number error.

The class1 grade 2 level reference net survey work started in 2002. It is based on the class 1 grade 1 level reference net survey results to carry out point selection, installation, survey and calculation work. At the present time, the level reference survey is completed. It is now proceeding with results calculation work.
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