ERF Variable

Description

v_sasv_delta

Self-adjusting space value delta.

SASV automatically adjusts the spacing value according to the typical spacing value the algorithm finds in the layer data, making for a faster spacing check.

 Statistical analysis shows that:

a) Spacing checks takes the biggest chunk of the SLA (Signal Layer Analysis) run time.

b) As the spacing search distance gets larger, the run time increases. (In fact, run time nearly quadruples.)

c) Usually, default values for the maximum spacing parameters are not adjusted to the data.

We believe there is no reason to search for spacing violations larger than the typical spacing interval. The SASV algorithm calculates this interval. A search using this value will be fast and efficient, and still give valid results.

How it works

1.      The algorithm randomly picks a small number of features and checks the spacing between them and their neighbors.

2.      It calculates the average value for those spacing measurments, and creates the typical spacing value.

3.      This value is multiplied by the value of the ERF variable v_sasv_delta .

4.      The action than uses this value for the spacing search. The action does not report spacing larger than this value, although it is smaller than pp_spacing .

The returned value must be larger than the ERF variable v_lower_sasv_limit . If the returned value if less than v_lower_sasv_limit,  it will use the value of v_lower_sasv_limit instead.

If the returned value is larger than pp_spacing , it will use the pp_spacing value.

The SASV value is reported in the special category: Self Adjust Spacing Value. It is also reported in the action summary and action attribute.

The SASV algorithm can be disabled by setting the ERF variable v_use_sasv = No (which is the default value of this ERF variable).