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This new electronic surveying instrument measures s/ope distance and zenith angle simultaneously, then computes and displays horizontal or vertical distance in feet or metres. /fs base measures horizontal angle. f N 1e70, WITH THE INTRODUCTION of the I saooA Distance Meter. Hewlett-Packard launched into the electronic measurement of distance. Since that time HP has become a major supplier of electronic distance measuring equipment (EDM). Typically, EDM has been used in conjunction with some angle measuring device such as a transit, because the position of one point with respect to another is usually described by a horizontal distance, a vertical distance, and a horizontal angle from a known bearing or line. Now both distance and angle measuring capability are available in a new instrument-the 38104 Total Station (Fig. r). In the past, horizontal distance was measured by taping the distance, being very careful to maintain the tape in a horizontal plane, or by measuring the slope distance (typically with EDM equipment), measuring the zenith angle (using a theodolite or transit), and then computing the horizontal distance on a calculator. The 3810A Total Station is capable of measuring slope distance and zenith angle simultaneously and then calculating the horizontal distance or vertical distance for immediate display. This horizontal distance capability, combined with a base that measures horizontal angle, makes the total station a powerful instrument for subdivision layout, as well as for many other surveying applications (see page 6). A glance at the total station's control panel (Fig. 2) shows not only its simplicity of operation but also the variety of measurement options selectable by the operator. The total station measures and displays either vertical, horizontal, or slope distance, or zenith angle. It gives a single reading to the full resolution of the inshument or continuously updated readings with reduced resolution. Readings are in feet or metres for distances and degrees/minutes/seconds or grads for angle. The operator simply preselects the desired function and units, aims the instrument at the target point using the integral telescope and aiming tangent screws, and presses the tvluAsunn button. The instrument then automatically controls its own measurement cycle to produce the desired readout. AII parameters other than the selected one are also measured or computed and are available for immediate recall. The continuously updated reading is especially useful for such things as laying out a certain distance. The total station measures distances up to 1.6 km [1 …