NAME
measerr - A program for determination of error in individual
discharge measurements
ABSTRACT
The uncertainty, or standard error, for individual measurements of
stream discharge is computed based on a root-mean-square error
analysis of the individual component errors. The component errors
include errors in the measurement of width, depth, and velocity, and
in computation procedures. The error in measurement of velocity
include the uncertainties introduced by the measurement instrument,
the pulsation of flow in natural rivers, the vertical distribution
of measurements, and oblique flow. This error analysis can be used
to evaluate the uncertainty for most discharge measurements made
with the vertical axis, cup-type current meter. The procedures do
not apply to other types of current meters or other methods such as
dilution gaging or ultrasonic methods. A USGS study indicates that
standard errors for individual discharge measurements can range from
about 2 percent under ideal conditions to about 20 percent when
conditions are poor and shortcut methods are used. Some conditions,
such as wind, ice, boundary effects, flow obstructions, improper
equipment, as well as incorrect measuring procedures and
carelessness, can result in larger errors than indicated by the
error analysis.
METHOD
The standard errors computed are at the 68 percent level of
significance (one standard deviation from the true value). That is,
68 percent of the measurements made under similar conditions are
expected to differ from the true value by less than one standard
error. The MEASERR program computes an estimate of the standard
error by computing the standard error of the individual error
components, and then combining these errors in a root-mean-square
error analysis to compute the overall standard error of the current-
meter discharge measurement.
HISTORY
Version 2.5 1994/04/19 - code clean-up and minor bug fixes
Release V930501 - version for use on DOS-based and the Data General
AViiON computers
Release B91.1.0, 6/91, author David Yancey, designed by Robert W.
Meyer, for Prime minicomputers, language: Fortran 77
DATA REQUIREMENTS
The program prompts the user for all necessary input and alerts the
user to acceptable ranges of input data. The required input data
include: 8- or 15- digit station identifier, optional textual
description of the measurement station, the measurement number, the
channel width, the cross-sectional area, the measured mean velocity,
the current-meter type, if horizontal flow were present, the average
observation time, the number of verticals measured, the number of
points measured in the vertical, the measurement type (waded,
suspended, or acoustic), and the channel-bed type. MEASERR can also
retrieve input from discharge-measurement data from a WATSTORE
OUTWAT retrieval. Required data not in the OUTWAT retrieval are
prompted for. Input data are expected in the U.S. customary units.
OUTPUT OPTIONS
The program displays the computed standard error and stores the
results in a text file. This file contains a summary of the input
data, computed standard error, and corresponding qualitative rating
(excellent, good, fair, or poor) for each discharge measurement.
SYSTEM REQUIREMENTS
MEASERR is written in Fortran 77 with the following extensions: use
of integer*2 declarations and use of adjustable size concatenation
of strings. MEASERR uses ANSI escape sequence to position text on
the screen and thus requires terminal emulation that supports these
escape sequences (for example, VT100 on UNIX-based systems and
ANSY.SYS loaded for DOS-based systems). Generally, the program is
easily installed on most computer systems. The code has been used
on UNIX-based computers and DOS-based 386 or greater computers
having a math coprocessor and 1 mb of memory.
DOCUMENTATION
Sauer, V.B., and Meyer, R.W., 1992, Determination of error in
individual discharge measurements: U.S. Geological Survey Open-
File Report 92-144, 21 p.
REFERENCES
Pelletier, P.M., 1988, Uncertainties in the single determination of
river discharge: a literature review: Canadian Journal of Civil
Engineering, v. 15, no. 5, p. 834-850.
TRAINING
Used in surface-water field and records techniques courses taught at
the regional level.
CONTACTS
Operation and Distribution:
U.S. Geological Survey
Hydrologic Analysis Software Support Program
437 National Center
Reston, VA 20192
h2osoft@usgs.gov
Official versions of U.S. Geological Survey water-resources analysis
software are available for electronic retrieval via the World Wide
Web (WWW) at:
http://water.usgs.gov/software/
and via anonymous File Transfer Protocol (FTP) from:
water.usgs.gov (path: /pub/software).
The WWW page and anonymous FTP directory from which the MEASERR
software can be retrieved are, respectively:
http://water.usgs.gov/software/measerr.html
--and--
/pub/software/surface_water/measerr
If you would like to obtain the price of and (or) order paper copies
of USGS reports, contact the USGS Branch of Information Services at:
U.S. Geological Survey
Branch of Information Services
Denver Federal Center, Box 25286
Denver CO 80225-0286
To inquire about Open-File Reports or Water-Resources Investigations
Reports:
Tel: 303-202-4210; Fax 303-202-4695
To inquire about other USGS reports:
Tel: 303-202-4700; Fax 303-202-4693