Design And Implementation Of The Water Velocity Of Flow Measurement System

The velocity and direction of flow is often referred to as the speed and direction of water1meter below the surface. It is an important indicator in the inland waterway maintenance management, and it is also an important reference basis in the channel evolution, the waterway transformation, the location of the pontoon bridge, and the driving navigation for large ship. A quick and accurate way to measure the flow rate of the river flow is an important topic of hydrology and hydrographic.Buoy observation method is the industry standard for the water velocity of flow measurement. Buoy generally adopt slender buoy, with the immersed part of1meter. When measuring, the buoys are placed along the direction of river’s width. According to the appropriate process, measure the average position once in a certain time. When the measurement is accomplished, mark the measuring point in the river drawings or CAD figure and connect the points into a line. Basing on the time of measurement and the distance between the calculated average velocities between two points, label the drawings and then the velocity flow graph is got.In the traditional way of measuring the velocity and direction of flow, theodolite intersection is the mostly often used way. One or several measurement stations should be set up when using this kind of way to measure. When the buoys flow though the river, the station near them will take the data. It is of low accuracy and labor consuming, and it can be affected by the visibility, the weather. As to long distance measure, it requires a lot of manpower and equipment investment.Due to the emergence of GPS positioning technology and its wide application, now, this technology is widely used in measuring the water velocity of flow. Through positioning the buoys by GPS, the velocity of flow can easily be got. This way can greatly reduce the complexity of the measurement, decrease the input for measuring equipment, and will not be affected greatly by visibility and weather.The precision of GPS is the key point in measuring the velocity of flow. The precision of civilian GPS is10meters, and it is far-more-enough for measuring. So as to improve the measuring accuracy of GPS, the pseudo range real-time differential positioning is usually adopted, with its accuracy of2meters; while the phase difference of real-time positioning RTK technology is even better, with its accuracy of decimeter or even centimeter level. When applying RTK technology to dual-frequency GPS receiver, the accuracy can reach millimeter level, and the precision is enough for the velocity of flow measurement.Differential GPS usually need data link in the process of measuring support to complete the data exchange between base station and mobile station. The mobile buoy USES the GPRS network communication; base station can be used in a fixed-line broadband communication, and it also can be used in the absence of fixed-line GPRS network; the tracker through Internet client directly connected with the measurements. In order to ensure the communication reliability, the data transmission adopts the TCP/IP protocol.This system uses the scheme of the main measurement process is as follows:(1) Prior to measure, the ship should be driven to the upstream of the river. Before reaching the measurement point, install the buoy to measuring buoy, open on the client, open the measuring buoy, onboard GPS power switch, and connect the onboard GPS into the client.(2) When approaching the measurement point, open tracker, buoys and base station, and wait for the tracking and buoy differential positioning to work smoothly. When the buoy differential positioning starts to work smoothly, put the buoys to measurement starting point, and wait for the start of the buoy after stability measurement.(3) When the buoys are floating in the river, the client in the ship can be used to monitoring the real-time position and tracking. After the buoys arrive at the measurement end points, go to the points by boat and salvage them. Close the buoys and the base station by client; remove the buoy from the buoy; close the buoy power and the measurement is accomplished.(4) After finishing the measurement, download the data from sever. Through processing the data with difference method, choosing the appropriate measurement points basing on the spacing requirements, labeling the map, exporting the AutoCAD drawing, the velocity flow figure is abstained.Basing on the initial way of measurement, this project improved the method to measure the velocity and direction of flow. Through application of differential GPS positioning technology, combining with wireless network technology and on Net platform of asynchronous Socket, we establish a stable, reliable, high precision of C/S structure of the measuring system. This system integrate buoy, tracking equipment and the base station, providing simple management and control functions, and can support the tracker, buoy position in channel real-time display on the drawing. The measurement system can greatly simplify the measuring process, the completion of rapid measuring homework, and map out results.