ucode(1) U.S. Geological Survey (wrdapp) ucode(1) NAME ucode - A Computer Code for Universal Inverse Modeling ABSTRACT UCODE is a computer program that performs inverse modeling, posed as a parameter-estimation problem, using nonlinear regression. Any application model or set of models can be used. An estimated parameter can be a quantity that appears in the input files of the application model(s), or that can be used in conjunction with user- defined functions to calculate a quantity that appears in the input files. An observation can be any quantity for which a simulated equivalent value can be produced, to which the regression will compare the observation. Simulated equivalent values can be produced by UCODE using values that appear in the application model output files and a set of additive and multiplicative functions. Prior, or direct, information on estimated parameters also can be included in the regression. METHOD The nonlinear regression problem is solved by minimizing a weighted least-squares objective function with respect to the parameter values using a modified Gauss-Newton method. Sensitivities needed for the method are calculated approximately by forward or central differences. HISTORY Version 1.0 1998/06/26 - Initial release. DATA REQUIREMENTS In order to use UCODE, the user must prepare a set of files that define parameters, how to generate input data for the application model(s) based on those parameters, observations, and how to generate simulated observations based on output data from the application model(s). OUTPUT OPTIONS Primary output is sensitivity of the observations to parameters and the estimated parameters that minimize the objective function. Other output includes statistics that describe how well the application models match the observations using the estimated parameters. SYSTEM REQUIREMENTS UCODE is intended for use on any computer operating system; it consists of algorithms programmed in perl, a freeware language designed for text manipulation, and Fortran 90, which efficiently performs numerical calculations. DOCUMENTATION Poeter, Eileen P. and Hill, Mary C., 1998, Documentation of UCODE, a computer code for universal inverse modeling: U.S. Geological Survey Water-Resources Investigations Report 98-4080, 116 p. 30 June 1998 1 ucode(1) U.S. Geological Survey (wrdapp) ucode(1) RELATED DOCUMENTATION Hill, Mary C., 1998, Methods and guidelines for effective model calibration: U.S. Geological Survey Water-Resources Investigations Report 98-4005, 90 p. TRAINING Parameter Estimation for the Modular Ground-Water Flow Model (GW3089TC), offered annually at the USGS National Training Center. 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 UCODE software can be retrieved are, respectively: http://water.usgs.gov/software/ucode.html --and-- /pub/software/ground_water/ucode 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: USGS Information Services Box 25286 Denver Federal Center Denver, CO 80225 To inquire about Open-File Reports or Water-Resources Investigations Reports: Tel: 303-202-4200; Fax 303-202-4695 To inquire about other USGS reports: Tel: 303-202-4700; Fax 303-202-4693 SEE ALSO modflowp - Parameter-estimation version of the modular model 30 June 1998 2