# Automatic Curve Matching

**singular-value decomposition**to perform automatic curve matching on challenging problems.

"I cannot imagine that I ever tried to analyze aquifer tests with manually plotted data curves using a light table. What a tremendous service you have provided with this software. Thank you."

--**Jim Borchers, USGS**

Match any aquifer test solution *objectively and efficiently* using **automatic curve matching**. AQTESOLV uses nonlinear weighted least-squares with singular-value decomposition to determine the optimal match between an aquifer test solution and your data.

Other useful options for automatic curve matching include curve fitting within a specified time window and matching only specified wells in your monitoring network.

## Nonlinear Least-Squares Curve Matching

Since its first release in 1989, AQTESOLV has led the way with the integration of visual and **automatic** curve-matching methods into a single software package for the analysis of aquifer test data.

AQTESOLV employs a powerful method of nonlinear weighted least-squares curve fitting (Marquardt 1963) to find the optimal match between solution curves and aquifer test data.

Only AQTESOLV combines automatic curve matching with informative statistical analyses to help you see how well your model fits the data.

## Singular-Value Decomposition

AQTESOLV now includes **singular value decomposition** (SVD), a powerful technique that improves the convergence of automatic curve matching (Press et al. 2002). When **SVD** is invoked, parameter corrections are
dampened by eliminating insensitive components from the updating equations.

**SVD** can yield convergence in certain difficult problems where other curve fitting algorithms may fail.

## Match Within Time Window

In some instances, it is advantageous to match an aquifer test solution over a specified range of time. AQTESOLV makes it easy with a **time window** for automatic estimation.

## Match Group of Wells

AQTESOLV allows you to analyze more than one observation well in pumping tests and slug tests. In the **Active Wells** property sheet, you may choose which wells to match during automatic estimation.