# Glossary

Average Elevation - Determined by calculating the area of the cross section and dividing it by the top width and subtracting from the top width elevation.

Bed Length - The sum of the lengths between each survey point along the cross section

Calculate and Store Cross Section Metrics – Cross Section Viewer calculates the cross section metrics to be used by tools within the software. This should be performed on any new database

Calculate Cross Section Spacing - Cross Section Viewer calculates the cross section spacing to be used by tools within the software. This should be performed on any new database

Closest Bank - L indicates that the defined station is closest to the channel margin left bank. R indicates the right bank

Construction Reference Plane (CRP) - A sloping datum on the Missouri River representing the stage, or water surface elevation met or exceeded 75% of the time during navigation season (source). In the software, any sloping datum is referred to as a CRP. It need not conform to the Missouri River definition.

Cross Section – Elevation vs. station at a transect across the river of a particular location along the river (i.e. river mile).

CRP Elevation - The elevation (in feet) of the sloping datum (called the CRP) at a given cross section.

Elevation - The vertical distance above a defined datum, typically sea level.

Lateral Change - Tool that generates plot of Bed Change vs. Depth Below Reference Plane between two Surveys with additional filtering by Selection, Reference Plane, Station, Cross Section, Plot Type. Used to describe how cross sections change with relation to depth or distance from a defined station (like a thalweg).

Long Profile - The long profile shows how a river’s gradient changes as it flows from its source to its mouth (source)

Longitudinal Change – Tool that generates plot of Cumulative Volume Change vs. River Mile for given Selection with additional filtering by Survey, Station, Vertical (Max cross section elevation) and River Mile

NAVD88 - “Is the vertical control datum of orthometric height established for vertical control surveying in the United States of America based upon the General Adjustment of the North American Datum of 1988” (source)

NGVD29 - “The Sea Level Datum of 1929 was the vertical control datum established for vertical control surveying in the United States of America by the General Adjustment of 1929. The datum was used to measure elevation (altitude) above, and depression (depth) below, mean sea level (MSL) … Since the Sea Level Datum of 1929 was a hybrid model, it was not a pure model of mean sea level, the geoid, or any other equipotential surface. Therefore, it was renamed the National Geodetic Vertical Datum of 1929 (NGVD 29) in 1973” (source)

Offset - The Euclidean distance of the point that was actually surveyed from the position on the monumented cross section that it represents*

Reference Stage – A fixed, horizontal line at a particular cross section.

Reference Station - One or more fixed vertical lines on a cross section.

River Bend - A knee or a meander in a river

River Mile - The longitudinal position of the cross section along the river

Sailing Line Distance - The high precision longitudinal position of the inflection point. Used to compute actual distance between cross sections.

Selections – A subset of available cross section locations. Also the name of the tool within the Cross Section Viewer that allows the user to create selections of cross sections based on desired attributes.

Station - The distance of the survey point from the left bank

Survey - A database record which includes information about the river survey including its name (often the date the survey was performed), extent of the survey (maximum and minimum river miles), number of cross sections, and any remarks

Survey Width - The euclidean distance between the first and last survey point

Vertical Datum - Vertical datum used for the cross section elevations (software currently allows for NAVD88 and NGVD29)

Whole River Miles - Points along the river corresponding with exact miles