New theodolites of British design and manufacture are a rarity and this new instrument represents a complete redesign of the old Watts Microptic No The first. A theodolite /θiːˈɒdəlaɪt/ is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes.Principles of operation · History · Use with weather balloons · Modern electronic. Microptic transit theodolite No 1, by Hilger & Watts Ltd, c. with box. (ex "Navigation Today" exhibition number: N.T.E. ). This instrument, devised in
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The axes and circles of a theodolite Diagram of an optical readout microptic theodolite Preparation for making sightings[ edit ] Main article: Temporary adjustments of theodolites Temporary adjustments are a set of operations microptic theodolite in order to make a theodolite ready for taking observations at a station.
These include its setting up, centering, leveling up and elimination of parallax, and are achieved in four steps: Setting up - fixing the theodolite onto a tripod along with approximate levelling and centering over the station mark.
Microptic theodolite - Oxford Reference
Centering - bringing the vertical axis of theodolite immediately over station mark using a centering microptic theodolite also known as a tribrach. Levelling - leveling of the base of the instrument to make the vertical axis vertical usually with an in-built bubble-level.
Focusing - removing parallax error microptic theodolite proper focusing of objective and eye-piece. The eye-piece only requires adjustment once at a station.
The objective will be re-focused for each subsequent sightings from this station microptic theodolite of the different distances to the target. Sightings[ edit ] Sightings are taken by the surveyor, who adjusts the telescope's vertical and horizontal angular orientation so the cross-hairs align with the microptic theodolite sighting point.
Both angles are read either from exposed or internal scales and recorded.
The next object is then sighted and recorded without moving the position of the instrument and tripod. The earliest angular readouts were from open vernier scales microptic theodolite visible to the eye. Gradually these scales were enclosed for physical protection, and finally became an indirect optical readout, with convoluted light paths to bring them to a convenient place on the instrument for viewing.
The modern microptic theodolite theodolites have electronic displays. Half of the difference between the two positions microptic theodolite called the "index error".
Theodolite: Surveying Tools | eBay
This can only be checked on transit instruments. Horizontal axis error - The horizontal and microptic theodolite axes of a theodolite must be perpendicular; if not then a "horizontal axis error" exists.
This can be tested by aligning the tubular spirit bubble parallel to a line between two footscrews and setting the bubble microptic theodolite.
Collimation error - The optical axis of the telescope, must also be perpendicular to the horizontal axis. If not, then a "collimation microptic theodolite exists.
Index error, horizontal-axis error 'trunnion-axis error' and collimation error are regularly determined by calibration and are removed by mechanical adjustment. Their existence is taken into account in the choice of measurement procedure in order to eliminate their effect on microptic theodolite measurement results of the theodolite.
History[ edit ] A theodolite ofshowing the open construction, and the altitude and azimuth microptic theodolite which are read directly. Sectioned theodolite showing the complex light paths for optical readout, and the enclosed construction.
Theodolite - Wikipedia
The term diopter was sometimes used in old texts as a synonym for theodolite. Prior to microptic theodolite theodolite, instruments such as microptic theodolite gromageometric square and various other graduated circles see circumferentor and semicircles see graphometer were used to obtain either vertical or horizontal angle measurements.
It was only a matter of time before someone put two measuring devices into a single instrument that could measure both angles simultaneously.