Offshore Pipeline Free Span Analysis

Dear Expert,
I'm involved in pipeline free span analysis of a offshore pipeline. I've read DNV-RP-105 and confuse about between In-line (or cross flow) onset span length and in-line (or cross flow) screening span length.
Could you explain to me what is the meaning of in-line onset span length? and what is the different between In-line (or cross flow) onset span length and in-line (or cross flow) screening span length?

Regards,
Steven

[QUOTE=steven tran;207677]Dear Expert,
I'm involved in pipeline free span analysis of a offshore pipeline. I've read DNV-RP-105 and confuse about between In-line (or cross flow) onset span length and in-line (or cross flow) screening span length.
Could you explain to me what is the meaning of in-line onset span length? and what is the different between In-line (or cross flow) onset span length and in-line (or cross flow) screening span length?

Regards,
Steven[/QUOTE]

In my opinion difference between "on line" an "in line" is as follow:
"On line" term is used when we make branch a line from mail line and it conveys flow as main line,but "in line" term is used when we assemble a line in parallel with main line.