Total-Station Data Collection And Input:
Survey data can be entered into a CAD program by a variety of techniques. The most favorable means is through a digital data file produced by electronic survey equipment. Total stations, GPS-S receivers, and some electronic levels are commonly capable of recording survey data on electronic data collectors. Such logging of data greatly increases the efficiency and accuracy of data collection and eliminates human error associated with field-note recording. These digital data files also eliminate the tedious and error-prone manual entry of data. Automatic data logging clearly offers a superior method for recording and processing survey angles, distances, or coordinates, but it does not eliminate the requirement for field notes. To establish complete survey records, field personnel must always record survey conditions, the project description, unplanned procedures, and any other pertinent information.
For total-station instruments, various software/hardware packages are available to collect and process survey data. The AISI and a CAD interface offer a full set of hardware and software for logging survey data, performing post processing and adjustments, and importing data into a PC workstation for further processing. CAD data-collection packages store the input of X, Y, and Z coordinates in the American Standard Code for Information Interchange (ASCII) format with a descriptor or code to indicate the surveyed feature along with alphanumeric description data. The data can then be managed into more complex and sophisticated packages of information to produce map products of great detail. The resulting product can then be plotted in hard copy or transferred into a more common format.
An automatic level uses a gravity-referenced prism or a compensator to orient the line of sight automatically. The instrument can be quickly leveled when a circular bubble level is used. When the bubble is centered, the compensator takes over and maintains a horizontal line of sight. Automatic levels are quick to set up and easy to use and can obtain second-order, Class II precision. The use of an automatic level entails using a freely moving prism that is suspended by a fulcrum or wire as a compensator. The compensator is sensitive to shock and must be kept nearly upright at all times. If the fulcrum or wire breaks, the instrument becomes useless. Gently tapping the instrument, while viewing through the telescope, will cause the line of sight to veer slightly. This verifies that the compensator is working properly.