File Format - PT2

Purpose

PT2 is a fixed-width ESCS point data format used by HAPI for ordinary survey record import and traverse diagram plotting.

General Architecture

PT2 is positional rather than delimited. The file should be interpreted using fixed-width substring slices. Whitespace should be stripped after slicing.

Positional Anatomy

Slice	Field
`[0:2]`	Record Status and Type
`[3:15]`	Northing
`[16:28]`	Easting
`[29:39]`	Reduced Level / Elevation
`[40:50]`	Point Code or Point Name, depending on mode
`[51:53]`	Link Code / Control ID
`[54:60]`	Point Number or Traverse Node Type

Record Status and Type

First Digit - Record Status

Digit	Status	Treatment
`0`	Active	Process as a normal shot.
`1`	Delete	Ignore the row.
`2`	Non-contourable	Treat as active.
`8`	Suppress R.L.	Treat as active.

Second Digit - Record Type

Digit	Type	Treatment
`0`	Normal Shot Level	Process as standard survey point.
`1`	Occupied Station	Process as Survey Control Station.

Mode A - Survey Record Mode

Used by A1a_Plot_Survey_Data_From_Point_Data_File.

Case	Treatment
Normal shot	Parse `[40:50]` as Point Code.
Occupied Station	Override Point Code to `STN`; parse `[40:50]` as Point Name.
Control ID Mapping	If `[51:53]` is not `00` or blank, prepend it to Point Name.

Mode B - Traverse Diagram Mode

Used by A2_Plot_Traverse_Diagram_From_File.

Case	Treatment
`NSTN`	New Station node.
`KSTN`	Known Station node.
`LEG`	Line-of-sight leg; group by pairing ID in `[51:53]`.

Edge Cases

Occupied Stations may have blank or alphanumeric point number fields. The old implementation note describes a retrospective lookahead method for assigning inferred point numbers.
Blank coordinate slices should be interpreted safely rather than causing a fatal numeric-cast failure.
Long alphanumeric station names may bleed into the point number area and should be treated as non-integer station metadata rather than a valid point number.

Source Basis

HAPI User Manual.pdf, Sections 2.3.1, 2.3.3, and 2.3.4.
File Format - PT2 File.md.