Rules from the Log ASCII Standards

LAS 1.2 (complete)

• Filename ends with ".las" (if loaded from a file)
• Last section in file is the data ~A section (also on line 424)
• ~ must be the first non-space and non-quotation character in a file
• Uppercase characters immediately following a ~ are "reserved for use by the committee" AKA no custom sections
• # can appear as the first non-space and non-quotation character on any line above the data section, and will then be treated as a comment line
• The ~V section must exist
• The ~V section should be the first in a file <- RECOMMENDATION ONLY
• The ~V section must have a VERS item containing fixed content
• The ~V section must have a WRAP item containing fixed content
• If unwrapped, the maximum line length in the entire file is 256 characters including \r and \n (also lines 430 to 432)
• If wrapped, the depth value in the data section will be on its own line (also line 434)
• If wrapped, all lines will be <= 80 chars including \r and \n (also line 436)
• The ~W section must exist
• A STRT item must exist in the ~W section
• A STOP item must exist in the ~W section
• A STEP item must exist in the ~W section
• If START's value is greater than STOP's value, then STEP must have a minus sign
• If the increment between depth values in the data section is variable then STEP should be zero
• A NULL item must exist in the ~W section
• A COMP item must exist in the ~W section
• A WELL item must exist in the ~W section
• A FLD item must exist in the ~W section
• A LOC item must exist in the ~W section
• Either PROV or all of CNTY, STAT, and CTRY items should be in the ~W section (or both? ambiguous)
• A SRVC item must exist in the ~W section
• A DATE item must exist in the ~W section
• Either a UWI or API item must exist in the ~W section
• The ~C section must exist
• All curves in the ~C section should exist in the data section
• Each column in the data section should be separated by at least one space (rules out CSV and TSV formats)
• In wrapped mode, decimal points must be vertically aligned in the data section
• Exponents are not permitted in the data section

LAS 2.0 (incomplete)

• Only the ASCII characters 10, 13 and 32-126 inclusive are permitted (others should be converted to spaces)
• Line termination should be ASCII 13 ASCII 10
• The data section should contain a continuous interval i.e. no repeat sections in the same file
• Filename ends with ".las" (if loaded from a file)
• Sections begin with a tilde as the first non-space character and are defined by the following character. Only one permitted per file. (and lines 159-168)
• Any customer defined sections - i.e. not V, W, C, P, O, or A - must be after the ~V section but before the ~A section
• Comment lines with # as the first non-space character can occur anywhere above the ~A section
• Every non-comment line in the ~V, ~W, ~C and ~P sections must contain at least a period, space, and colon in that order
• Every non-comment line in the ~V, ~W, ~C and ~P sections must not contain a colon before the first period
• Every non-comment line in the ~V, ~W, ~C and ~P sections must only contain spaces at the start and end of the mnemonic, not in the middle
• Every non-comment line in the ~V, ~W, ~C and ~P sections: any characters immediately following the first period in the line are the unit, and these cannot contain a colon
• Every non-comment line in the ~V, ~W, ~C and ~P sections: any characters after the first space following the first period are the data, and must be to the left of the last colon in the line - ambiguous what "to the left" means - one space?
• The ~V section must exist
• The ~V section must be the first section - Note this is a requirement whereas in LAS 1.2 it was a recommendation.
• The ~V section must have a VERS item containing fixed content
• The ~V section must have a WRAP item containing fixed content
• If wrapped, all lines will be <= 80 chars including \r and \n

LAS 3.0 (incomplete)