Who this entry is for — Readers who want to construct and interpret an FLD without reducing it to the imprecise formula “price shifted half a period”.
Source boundary — The Profit Magic of Stock Transaction Timing (1970) was checked as the primary source for envelopes, displaced averages and VTLs; it does not document the FLD under this name and construction. The original Cycles Course is not available in the Cyclepedia corpus, so every attribution to the course is indirect. The three variants, offsets and uses below were checked directly against David Hickson / Sentient Trader's post-Hurst documentation, not against the course.
Prerequisites
Phasing analysis, cycle period and underlying trend.
Definition
In plain terms — An FLD retains the shape of a price series and moves it to the right. Its offset is about half the cycle's wavelength, but the documented convention changes by one bar according to the series and use.
For a wavelength P measured in bars, Sentient Trader's post-Hurst documentation distinguishes three FLDs:
| Variant | Shifted series | Offset | Documented use |
|---|---|---|---|
| Median-FLD | (High + Low) / 2 |
⌊P / 2⌋ + 1 bars |
Confirm troughs and peaks after the bar is complete |
| High-FLD | High | ⌊P / 2⌋ bars |
Immediate buy action signal |
| Low-FLD | Low | ⌊P / 2⌋ bars |
Immediate sell action signal |
The distinction prevents a median-price crossing, which is known only after the bar's high and low are final, from being treated as an intrabar signal.
Example — With P = 20, the median-FLD uses an 11-bar offset, while the high- and low-FLDs use 10. With P = 21, the offsets remain 11 and 10 respectively because the half-wavelength is truncated.
Crossings and confirmations
In plain terms — A crossing does not create a turning point. Within this framework it is used as evidence that the trough or peak assigned to the cycle has already formed.
Under the convention documented by Hickson / Sentient Trader:
- an upward crossing confirms a trough of the associated cycle;
- a downward crossing confirms a peak;
- median-FLD confirmation is evaluated with the completed bar's median price;
- high- and low-FLDs provide levels for immediate action signals.
The wavelength must come from a coherent phasing analysis. Changing P changes the offset and therefore the line. The future segment is known only while the input series and wavelength convention remain fixed; an adaptive implementation that recalibrates the period may update its output.
Price projection
In plain terms — The distance between a turning point and the crossing is reflected beyond the crossing. This is a model projection, not an order or a guarantee.
For an upward crossing at price C, with an observed trough at L:
Upward target = C + (C − L) = 2C − L
For a downward crossing at price C, with an observed peak at H:
Downward target = C − (H − C) = 2C − H
The Sentient Trader help describes the corresponding time projection as less accurate and suitable only as a rough guide.
Example — Trough 90, upward crossing 96: projected price 102. The calculation reflects the six points already travelled; it assigns no probability to reaching 102 and does not include trend, volatility or costs.
FLD and VTL
| Graphical VTL | FLD | |
|---|---|---|
| Construction | Straight line selected within an expected cyclic window | Shifted price series |
| Event | Break of the line | Crossing of price and line |
| Dependency | Pivots and time window | Wavelength and high/low/median series |
| Projection | Other tools in the method | Symmetry around the crossing |
In the tradition described by Hickson, FLDs and VTLs are used with phasing and longer cycles. This is an accessible post-Hurst formalisation; it does not by itself establish that every implementation detail was identical in the original course. Neither line removes false signals, dating errors or execution risk.
Limits
- It is a tool of the Hurst tradition as formalised by Hickson, not a universal empirical law.
- An incorrect period or phasing produces a miscalibrated line.
- Several cycles and trends contribute to price; the ideal wave is not the full observed series.
- A crossing is an analytical condition, not financial advice.
- Targets and timing require validation for the market, timeframe, data and costs concerned.
Common mistake — Applying round(P/2) indiscriminately to every FLD. The checked convention distinguishes truncation, the median-FLD's additional bar and high/low series for immediate signals.
Summary card
- Median-FLD: median price,
⌊P / 2⌋ + 1, completed-bar confirmation. - High/Low-FLD: high or low,
⌊P / 2⌋, immediate levels. - Projection: turning-point-to-crossing distance reflected beyond the crossing.
- Context: phasing, underlying trend and risk remain necessary.
Sources
- J. M. Hurst, The Profit Magic of Stock Transaction Timing, Prentice-Hall, 1970, Ch. 4, pp. 69–85 — primary source for envelopes, displaced averages, the state table and VTLs; used here to delimit the book's method, not as a source for the FLD.
- David Hickson / Sentient Trader, FLD's — Future Lines of Demarcation — direct post-Hurst source for the three variants, offsets, confirmations and projections.
- David Hickson / Sentient Trader, Hurst's Trading Methodology — post-Hurst account attributing the methodology to the Cycles Course and distinguishing delayed confirmation from immediate action signals; the original course was not checked.
The two web sources belong to the same Hickson / Sentient Trader documentation and are not independent confirmations.