![]() ![]() The modern digital theodolites have electronic displays.Įrrors in measurement Index error The angles in the vertical axis should read 90 ° (100 grad) when the sight axis is horizontal, or 270° (300 grad) when the instrument is transited. 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 earliest angular readouts were from open vernier scales directly visible to the eye. The next object is then sighted and recorded without moving the position of the instrument and tripod. Both angles are read either from exposed or internal scales and recorded. Sightings are taken by the surveyor, who adjusts the telescope's vertical and horizontal angular orientation so the cross-hairs align with the desired sighting point. The objective will be re-focused for each subsequent sighting from this station because of the different distances to the target. The eye-piece only requires adjustment once at a station.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |