Although the methods for accurately measuring bed-material load are still lacking, new technology, improvements in existing technology, and application of instruments used in hydrographic surveying and oceanographic research have made the collection of the bathymetric and hydraulic data feasible. Range-azimuth tracking systems are similar to total stations used for land surveying. The tracking system must be located where the operator can manually track a reflector mounted on the boat. During floods this can be a significant problem. Real-time, kinematic, DGPS allows for rapid collection of velocity and bathymetric data in open areas, but data collection near tree lines and bridges is hampered by loss of adequate satellite coverage caused by blockage of the sky by trees and bridge structure.
Acoustics are the primary means of collecting streambed-elevation and velocity data.
A digital echo sounder with analog paper chart is the preferred instrument for making detailed bathymetric surveys. For inland waterway applications, an echo sounder operating at a frequency of 200 kHz, with three-degree transducer, and with a peak digitization algorithm generally works well. This instrument provides a good balance between the resolution of the acoustic signal and penetration of deep or sediment-laden waters. By use of trigonometric relations and the geometric arrangement of the beams, three-dimensional velocity vectors are computed for each depth cell. Thus, velocities can only be measured where the flow within a layer of the velocity profile is reasonably homogeneous through all of the beams.