The Vertical Horizontal Filter ("VHF") determines whether prices are in a trending phase or a congestion phase. The VHF was first presented by Adam White in an article published in the August, 1991 issue of Futures Magazine.
Probably the biggest problem in technical analysis is determining if prices are trending or are in a trading-range. The VHF indicator attempts to determine the "trendiness" of prices to help you decide which indicators to use.
There are three major ways to interpret the VHF indicator:

Relative Momentum Index
Relative Momentum Index (RMI) is a variation of the RSI indicator. The RMI counts up and down days from the Close relative to the Close X days ago (where X is not limited to 1 as is required by the RSI) instead of counting up and down days from Close to Close as the RSI does.
Moving slope rate of change - Extended
Extended version of MSROC indicator.
Ulcer Index
This Ulcer Index indicator was derived from the stock risk indicator by Peter Martin in the 1987 book "The Investors Guide to Fidelity Funds".
Chandes Quick Stick (Qstick)
Chandes Quick Stick (Qstick)