What is a theodolite and how to used Theodolite

A theodolite is a measuring instrument invented in the late 18th century. It was used as an early surveying tool, and was extremely acurate. Thomas Jefferson used such an instrument during his time as a surveyor. Later versions are also known as "Dumpy Theodolite", while 20th century versions use extremely fine optics, or lasers. The tool in it's present,modern versions is indespensible as a surveying/mapping tool.

Process of Measuring Horizontal Angles Using a Theodolite

1. Setting up the Theodolite: This includes mounting the theodolite on a tripod and making sure it is comfortable for the user.

2. Unlock the upper horizontal clamp.

3. Rotate the theodolite until the arrow in the upper or lower rough sight points to the feature of interest and lock the clamp.

4. Look through the main eyepiece and use the upper horizontal adjuster to align the vertical lines on the feature of interest.

5. The reading is taken by looking through the small eyepiece. Using the minutes and seconds adjuster set the one of the degrees on the horizontal scale so the single vertical line on the bottom scale is between the double vertical lines under the selected degree.

6. The reading is the degree which has been aligned and the minutes and seconds read from the right hand scale and is the horizontal angle from the reference line.

Process of Measuring Vertical Angles Using a Theodolite

Process of Measuring Vertical Angles

1. Setting up the Theodolite: This includes mounting the theodolite on a tripod and making sure it is comfortable for the user.

2. Unlock the vertical clamp and tilt the eyepiece until the point of interest is aligned on the horizontal lines. Lock the clamp in place.

3. Looking through the small eyepiece, use the minutes and seconds adjuster to align one of the degrees on the vertical scale with the double lines just below it.

4. The reading is the degree that has been aligned and the minutes and seconds is read from the right hand scale.

5. To complete the reading, it may be necessary to measure the distance from the theodolite to the point of interest.

Tata Cara Pengukuran Detil Cara Tachymetri Menggunakan Theodolit Berkompas

Pengukuran detil cara tachymetri dimulai dengan penyiapan alat ukur ( Theodolite )titik ikat dan penempatan rambu di titik bidik. Setelah alat siap untuk pengukuran, dimulai dengan perekaman data di tempat alat berdiri, pembidikan ke rambu ukur, pengamatan azimuth dan pencatatan data di rambu BT, BA, BB serta sudut miring m.

• Tempatkan alat ukur theodolite di atas titik kerangka dasar atau titik kerangka penolong dan atur sehingga alat siap untuk pengukuran, ukur dan catat tinggi alat di atas titik ini.
• Dirikan rambu di atas titik bidik dan tegakkan rambu dengan bantuan nivo kotak.
• Arahkan teropong ke rambu ukur sehingga bayangan tegak garis diafragma berimpit dengan garis tengah rambu. Kemudian kencangkan kunci gerakan mendatar teropong.
• Kendorkan kunci jarum magnet sehingga jarum bergerak bebas. Setelah jarum setimbang tidak bergerak, baca dan catat azimuth magnetis dari tempat alat ke titik bidik.
• Kencangkan kunci gerakan tegak teropong, kemudian baca bacaan benag tengah, atas dan bawah serta cata dalam buku ukur. Bila memungkinkan, atur bacaan benang tengah pada rambu di titik bidik setinggi alat, sehingga beda tinggi yang diperoleh sudah merupakan beda tinggi antara titik kerangka tempat berdiri alat dan titik detil yang dibidik.

Kesalahan pengukuran cara tachymetri dengan theodolite berkompas

• Kesalahan alat, misalnya:
  a. Jarum kompas tidak benar-benar lurus.
  b. Jarum kompas tidak dapat bergerak bebas pada prosnya.
  c. Garis bidik tidak tegak lurus sumbu mendatar (salah kolimasi).
  d. Garis skala 0° - 180° atau 180° - 0° tidak sejajar garis bidik.
  e. Letak teropong eksentris.
  f. Poros penyangga magnet tidak sepusat dengan skala lingkaran mendatar.
• Kesalahan pengukur, misalnya:
  a. Pengaturan alat tidak sempurna ( temporary adjustment ).
  b. Salah taksir dalam pemacaan
  c. Salah catat, dll. nya.
• Kesalahan akibat faktor alam, misalnya:
  a. Deklinasi magnet.
  b. atraksi lokal.

• Titik detil yang harus diukur meliputi semua titik alam maupun buatan manusia yang mempengaruhi bentuk topografi peta daerah pengukuran.