Wednesday, May 14, 2008

Advanced vs. Standard Versions in Vistas

A common question I get about Groundwater Vistas is "what is the difference between advanced and standard versions"? Here is a quick summary of features found in the advanced and enterprise versions that are not in the standard version:

- Recharge/ET memory compression
- Support for the HUF Package (Hydrogeologic Unit Flow)
- Support for SWIFT
- Monte Carlo modeling for analysis of uncertainty
- Pest's SVD Assist automation
- Pest's Null Space Monte Carlo technique

Recharge and ET memory compression is useful when you are running a large model that has lots of stress periods. Normally GV allocates enough memory to hold all recharge and ET values for all stress periods. As models get larger and more transient, that presents a problem whereby there is just not enough memory to hold it all. In the advanced version, when GV sees this problem, it uses a compression algorithm (like WinZip) to compress the arrays. They are still stored in memory, just in compressed form.

Pest's SVD Assist is a technique that allows for much faster run times when you are trying to estimate a large number of parameters. It also removes the problem of trying to estimate insensitive parameters. Parameters are grouped into "super" parameters that are linear combination of the real parameters. Only super parameters are estimated. This usually results in about a ten-fold decrease in the number of parameters to estimate. In GV, we have made the use of this complex technique relatively simple.

Pest's Null Space Monte Carlo technique builds on the SVD Assist calibration technique. It allows you to create multiple realizations of your model that are all calibrated to a desired level of calibration quality. In the past, calibrating each realization of a monte carlo simulation was not feasible due to long model run times. Special features in the Pest technique, along with the use of SVD Assist, allows you to calibrate many realizations in a relatively short period of time. Like SVD Assist, GV has made the use of this technique straightforward.

The Enterprise version of Vistas is the same as Advanced but also adds Remote Model Launch (RML) and GW3D for 3D visualization of model results.


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