Chapter 4 -- TABLES Section
UCS

The following group codes apply to UCS symbol table entries. In addition to the group codes described here, see "Common Group Codes for Symbol Table Entries." For information about abbreviations and formatting used in this table, see "Formatting Conventions in This Reference."

UCS group codes
Group codes Description

100

Subclass marker (AcDbUCSTableRecord)

2

UCS name

70

Standard flag values (bit-coded values):
16 = If set, table entry is externally dependent on an xref.
32 = If this bit and bit 16 are both set, the externally dependent xref has been successfully resolved.
64 = If set, the table entry was referenced by at least one entity in the drawing the last time the drawing was edited. (This flag is for the benefit of AutoCAD commands. It can be ignored by most programs that read DXF files and need not be set by programs that write DXF files.)

10

Origin (in WCS)
DXF: X value; APP: 3D point

20, 30

DXF: Y and Z values of origin (in WCS)

11

X-axis direction (in WCS)
DXF: X value; APP: 3D vector


21, 31

DXF: Y and Z values of X-axis direction (in WCS)

12

Y-axis direction (in WCS)
DXF: X value; APP: 3D vector


22, 32

DXF: Y and Z values of Y-axis direction (in WCS)

79

Orthographic view type:
0 = UCS is not orthographic;
1 = Top; 2 = Bottom;
3 = Front; 4 = Back;
5 = Left; 6 = Right

146

Elevation

346

ID/handle of base UCS if this is an orthographic. This code is not present if the 79 code is 0. If this code is not present and 79 code is non-zero, then base UCS is assumed to be WORLD.

71

Orthographic type (optional; always appears in pairs with the 13, 23, 33 codes):
1 = Top; 2 = Bottom;
3 = Front; 4 = Back;
5 = Left; 6 = Right

13

Origin for this orthographic type relative to this UCS.
DXF: X value of origin point; APP: 3D point

23, 33

DXF: Y and Z values of origin point

Each 71/13,23,33 pair defines the UCS origin for a particular orthographic type relative to this UCS. For instance if the following pair is present, then invoking the UCS/LEFT command when UCSBASE is set to this UCS will cause the new UCS origin to become (1,2,3).

71: 5
13: 1.0
23: 2.0
33: 3.0

If this pair were not present, then invoking the UCS/LEFT command would cause the new UCS origin to be set to this UCS's origin point.