1	Water in Motion And Motion in Water
2	4-Beam Solution vs. 3-beam systems Reliability Improved likelihood for greater success in adverse conditions Quality Unique basis for screening raw data and so producing higher quality results Performance More precise data and unique measurements not possible with 3 beams
3	4-Beam Solution vs. 3-beam systems For optimal conditions, 3 beams are sufficient for measuring 3-d motion But how often are field conditions optimal?Ý More often field conditions are demanding So the prudent operator will rely on more than the minimum requirement
4	Engineering Advantages of 4 Beams More information about currents through water column, vehicle velocity over bottom Ping-by-ping evaluation of data quality permits identifying outliers before they corrupt the average value Measurement redundancy for each layer in current profile and in bottom tracking More adaptable configuration for difficult measurement situations
5	Reliability (1) The 4th beam improves your likelihood for greater success in adverse conditions Provides back-up or redundant capability, acting as a fail-safe when the unfortunate happens Reduces concern about lost time, having to repeat work, and coming home empty-handed 3-d velocities can still be computed even if one beam is blocked or damaged, degraded by fish, faded at depth
6	Reliability (2) The 4th beam improves your likelihood for greater success in adverse conditions Allows deployment flexibility, keep working around underwater obstructions Produces superior bottom tracking results, reduces dropouts Enhances operator safety in floods, reliable results reduce time required on the water
7	Quality The 4th beam enables a unique screening of raw data, producing higher quality results Evaluates how well all beams see the same flow field => affects noise, bias in data Provides a quantitative basis for QA/QC at each depth layer of each ping Enables superior screening of raw data, allows greater certainty of quality of results
8	Quality--Error Velocity (1) The 4th beam enables a unique screening of raw data, producing higher quality results Provides a far more sensitive screen for data quality than can be achieved by inspecting echo intensity Establishes a unique and independent basis for addressing questions about data quality
9	Quality--Error Velocity (2) The 4th beam enables a unique screening of raw data, producing higher quality results Screens each ping for unacceptable noise in the data e.g., due to fish, turbulence, or eddy variability Detects consistent obstructions from solid scatterers => causing bias in the data Provides an adaptive measure of the variance of horizontal flow
10	Performance (1) The 4th beam allows better precision & measurements not possible with 3 beams ÝA 4-beam system has 25% less variance than a 3-beam system Produces lower standard deviation in the data and allows shorter averaging times Enables improved navigation and finer along-track resolution
11	Performance (2) The 4th beam allows better precision & measurements not possible with 3 beams Consumes NO more energy than a 3-beam system (for same noise in data) Janus Configuration enables scientific measurements not possible with 3 beams e.g., Reynolds stress estimation for sediment transport or mixing
12	4-Beam Solution vs. 3-beam systems Reliability Improved likelihood for greater success in adverse conditions Quality Unique basis for screening raw data and so producing higher quality results Performance More precise data and unique measurements not possible with 3 beams