CH Cheat Sheet 2026

The 30 highest-yield CH facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. In an ADCP measurement, what does the term 'ensemble' refer to? → The average of multiple pings collected over a short interval
2. What is peer review in CH Environmental Impact Assessment? → Quality evaluation by qualified colleagues for improvement
3. What is the importance of continuing education for CH professionals in Environmental Impact Assessment? → Maintaining current knowledge and adapting to industry changes
4. The speed of sound used by an ADCP to convert travel time to range is primarily a function of: → Water temperature, salinity, and pressure (depth)
5. Which ADCP blanking distance parameter defines the zone nearest the transducer where velocity data cannot be reliably collected? → Blank before transmit
6. Converting raw satellite digital number values to surface reflectance is accomplished through: → Radiometric calibration followed by atmospheric correction
7. The International Hydrographic Organization (IHO) publication 'S-44' primarily establishes: → Minimum standards for hydrographic survey accuracy by order classification
8. What is the primary horizontal datum used for nautical charts produced by NOAA in the United States? → NAD 83 / WGS 84
9. What is the primary source of uncertainty in ADCP discharge measurements caused by the region near the water surface? → The unmeasured top layer due to blanking distance and draft
10. Which type of satellite sensor is most commonly used to measure sea surface temperature (SST) in hydrographic studies? → Thermal Infrared (TIR) sensor
11. What is Mean Lower Low Water (MLLW)? → Average of the lower low tides each day over 19 years
12. How does professional liability insurance protect CH practitioners? → Covering financial losses from claims of negligence or errors
13. What is backup and disaster recovery for in CH technology? → Ensuring data restoration and operations resumption after failures
14. Which test is performed to detect a moving bed condition during ADCP field measurements? → Stationary moving bed test with vessel anchored or held fixed
15. Why are vertical datums important in hydrography? → They provide a height reference for soundings
16. What is a needs assessment in CH Conservation & Sustainability practice? → Identifying gaps between current conditions and desired outcomes
17. What differentiates quality assurance from quality control in CH? → QA prevents defects through processes; QC detects defects in outputs
18. According to USGS Techniques and Methods 3-A22, the recommended minimum number of transects for a standard ADCP discharge measurement is: → 4 transects
19. Which of the following instruments is used to measure the depth of the seafloor? → Single-beam echo sounder
20. What is the primary function of a multibeam echo sounder in hydrographic surveying? → Mapping underwater features using multiple beams
21. What is an SLA in CH technology? → A formal agreement defining expected service performance standards
22. What is the importance of continuing education for CH professionals in Conservation & Sustainability? → Maintaining current knowledge and adapting to industry changes
23. Which of the following satellite datasets is freely available and widely used for large-area coastal monitoring and satellite-derived bathymetry research? → Sentinel-2 (ESA Copernicus program)
24. What is evidence-based practice in CH Environmental Impact Assessment? → Integrating research evidence with expertise and client needs
25. With both Sentinel-2A and Sentinel-2B satellites operating, the approximate revisit interval at the equator is: → 5 days
26. How do regulations differ from standards in CH practice? → Regulations are legally binding; standards are typically voluntary
27. What does the 'error velocity' output from a four-beam ADCP indicate? → Inconsistency between redundant beam-pair velocity solutions, flagging data quality
28. What is a quality audit in CH practice? → Evaluating whether quality standards and procedures are followed
29. Synthetic Aperture Radar (SAR) is particularly valuable for hydrographic applications because it can: → Detect oil spills, ship wakes, and surface roughness regardless of cloud cover or darkness
30. Why is sound velocity profiling important in bathymetric surveys? → To correct echo sounder data for refraction