For explanation with pictures of the aligned dimension:
https://documentation.help/AutoCAD-DXF/WS1a9193826455f5ff18cb41610ec0a2e719-7a26.htm
for radial and diameter dimension:
https://documentation.help/AutoCAD-DXF/WS1a9193826455f5ff18cb41610ec0a2e719-7a21.htm


possible values for Code 70 Dimension type:
Values 0-6 are integer values that represent the dimension type. 
Values 32, 64, and 128 are bit values, which are added to the integer values (value 32 is always set in R13 and later releases)

0 = Rotated, horizontal, or vertical; 1 = Aligned; 2 = Angular; 3 = Diameter; 4 = Radius; 5 = Angular 3 point; 6 = Ordinate
32 = Indicates that the block reference (group code 2) is referenced by this dimension only
64 = Ordinate type. This is a bit value (bit 7) used only with integer value 6. If set, ordinate is X-type; if not set, ordinate is Y-type
128 = This is a bit value (bit 8) added to the other group 70 values if the dimension text has been positioned at a user-defined location rather than at the default location


possible values for Code 71 Attachment point:
1 = Top left; 2 = Top center; 3 = Top right
4 = Middle left; 5 = Middle center; 6 = Middle right
7 = Bottom left; 8 = Bottom center; 9 = Bottom right


Example values are taken from the file "dxf issues with special chars.dxf"


Example of a vertical (90° rotated) dimension 17.5cm:

  0
DIMENSION
...
  8
0_WP_BEMASSUNG_1_50
100
AcDbDimension
...
  2
*D19
 10 -- point where dimension line starts
-5.066473011211921
 20
18.65497213215147
 30
0.0
 11 -- center point of dimension text 
-5.066473011211921
 21
18.0571371290556
 31
0.0
 70 -- dim type
   160
  1 -- dim user text
<>
 71 -- dimension text attachment point
     5
 42 -- actual measured value , read only
0.1750000000000007
...
100
AcDbAlignedDimension
 13 -- defines the start point of reference line
-4.299999375712105
 23
18.47997213215147
 33
0.0
 14 -- defines the end point of reference line
-4.549999375711014
 24
18.65497213215147
 34
0.0
 50 -- Angle of rotated, horizontal, or vertical dimensions. rotation angle in ° measured from North Up, present, if dim. type is 0, ignore otherwise. 
90.0  -- example: dimension line is 90° , which means the extension line points to the left from the ref end point (14,24,34). 
      -- it describes the rotation from (0,1,0) to the extension vector (10,20,30)-(14,24,34). In fact we do not need this as the vector should be enough
100
AcDbRotatedDimension -- this only is present, if it is rotated dimension, meaning code dim type is 0 and above code 50 is also there
...


#Transform for SketchUp:
# DXF codes indicated in variables starting with p (point) or v(vector) or c(any code):

# dimension line start point
p10 = "-5.066473011211921m".to_l
p20 = "18.65497213215147m".to_l
p30 = "0.0m".to_l
# Text center point
p11 = "-5.066473011211921m".to_l
p21 = "18.0571371290556m".to_l
p31 = "0.0m".to_l
# reference start point
p13 = "-4.299999375712105m".to_l
p23 = "18.47997213215147m".to_l
p33 = "0.0m".to_l
# reference end point
p14 = "-4.549999375711014m".to_l
p24 = "18.65497213215147m".to_l
p34 = "0.0m".to_l
# dimension type
c70 = 160
# user text
c1 = "<>"
# attachment point
c71 = 5
# actual measurement
c42 = "0.1750000000000007m".to_l
# roatation angle, present if dimension type is 0. 90 means the extensionline is pointing horizontally to the left
c50 = 90.0 







Example of a 150° rotated dimension 0.1045m: (this is not in the test file, but explains the rotation)

  0
DIMENSION
...
100
AcDbDimension
...
  2
*D19
 10  -- dimension line start point
-8.899926547821183
 20
17.72716123057153
 30
0.0
 11  -- text center position
-7.739084203853859
 21
16.90682894883902
 31
0.0
 70 -- the dim type, se above. here it means 0 = rotated dim
    32
  1  -- user text. between angle brackets is the measured value
Uwe <>
 71  -- attachment point place
     5
 42 -- actual measurement, read only
0.1045286148822958 
...
100
AcDbAlignedDimension
 13
-8.864999375716582
 23
18.01577671607208
 33
0.0
 14
-8.715987007018034
 24
18.07349931765649
 34
0.0
 50 -- Angle of rotated, horizontal, or vertical dimensions. rotation angle in ° measured from North Up, present, if dim. type is 0, ignore otherwise. 
152.0273083652495
       -- example: dimension line is 152° , which means the extension line points to the left downwards from the ref end point (14,24,34). 
      -- it describes the rotation from (0,1,0) to the extension vector (10,20,30)-(14,24,34). In fact we should not need this as the vector should be enough
100
AcDbRotatedDimension -- this only is present, if it is rotated dimension, meaning code dim type is 0 and above code 50 is also there
...




#Transform for SketchUp:
# DXF codes indicated in variables staring with p (point) or v(vector) or c(any code):

# dimension line start point
p10 = "-8.899926547821183m".to_l
p20 = "17.72716123057153m".to_l
p30 = "0.0m".to_l
# Text center point
p11 = "-7.739084203853859m".to_l
p21 = "16.90682894883902m".to_l
p31 = "0.0m".to_l
# reference start point
p13 = "-8.864999375716582m".to_l
p23 = "18.01577671607208m".to_l
p33 = "0.0m".to_l
# reference end point
p14 = "-8.715987007018034m".to_l
p24 = "18.07349931765649m".to_l
p34 = "0.0m".to_l
# dimension type
c70 = 160
# user text
c1 = "Uwe <>"
# attachment point
c71 = 5
# actual measurement
c42 = "0.1045286148822958m".to_l
# roatation angle, present if dimension type is 0
c50 = 152.0273083652495






Example of aligned dimension that is vertical with measure 1.245
  0
DIMENSION
...
  8
0_WP_BEMASSUNG_1_50
100
AcDbDimension -- this defines the dimension line 
  8 -- layer where the dimension is attached
0_WP_BEMASSUNG_1_50
...
  2 -- Name of the block that contains the entities that make up the dimension picture like MText, arrow heads, etc,
*D21 
 10 -- point where dimension line starts
-14.58656601344108
 20
20.01997210955141
 30
0.0
 11 -- center point of dimension text 
-14.58656601344108
 21
19.52440523079339
 31
0.0
 70 -- dim type values 0,1,2,3,4,5,6, 32, 64, 128 added up, e.g. 161 = 128 + 32 + 1 = dim text is user defined and it is an aligned dim
  161 -- 1 is an aligned dim, i.e. dimension line is parallel to reference (measure) line
  1 -- dimension text, if missing or empty or <>, then use measured value from 42
<>
 71 -- attachement point , in case we have to rotate the dimension line. values 1-9
     5 -- middle center
 42 -- Actual measurement (optional; read-only value). probably always there, if no text in code 1
1.24499997739936
...
100
AcDbAlignedDimension
...
 13 -- defines the start point of reference line: from where we measure. it is also the start point for the first extension line
-14.194999375716
 23
18.77497213215205
 33
0.0
 14 -- defines the end point of reference line: to where we measure. it is also the start point for the second extension line
-14.194999375716
 24
20.01997210955141
 34
0.0
...



#Transform for SketchUp:
# DXF codes indicated in variables staring with p (point) or v(vector) or c(any code):

# variable assignment for later sketchup commands

# dimension line start point
p10 = "-14.58656601344108m".to_l
p20 = "20.01997210955141m".to_l
p30 = "0.0m".to_l
# Text center point
p11 = "-14.58656601344108m".to_l
p21 = "19.52440523079339m".to_l
p31 = "0.0m".to_l
# reference start point
p13 = "-14.194999375716m".to_l
p23 = "18.77497213215205m".to_l
p33 = "0.0m".to_l
# reference end point
p14 = "-14.194999375716m".to_l
p24 = "20.01997210955141m".to_l
p34 = "0.0m".to_l
# dimension type
c70 = 161
# user text
c1 = "<>"
# attachment point
c71 = 5
# actual measurement
c42 = "1.24499997739936m".to_l
# roatation angle, present if dimension type is 0
c50 = 0 # not present here





Example of aligned dimension that is horizontal with measure 2.885m
  0
DIMENSION
...
  8 -- the layer/tag
0_WP_BEMASSUNG_1_50
100
AcDbDimension -- this defines the dimension line 
  8 -- layer where the dimension is attached
0_WP_BEMASSUNG_1_50
...
  2 -- Name of the block that contains the entities that make up the dimension picture like MText, arrow heads, etc,
*D21 
 10 -- point where dimension line starts
-5.829999375710795
 20
19.10976678735829
 30
0.0
 11 -- center point of dimension text 
-6.101444903469229
 21
19.18676678843117
 31
0.0
 70 -- dim type values 0,1,2,3,4,5,6, 32, 64, 128 added up, e.g. 161 = 128 + 32 + 1 = dim text is user defined and it is an aligned dim
   161 -- 1 is an aligned dim, i.e. dimension line is parallel to reference (measure) line
  1 -- dimension text, if missing or empty or <>, then use measured value from 42
<>
 71 -- attachement point , in case we have to rotate the dimension line. values 1-9
     5 -- middle center
 42 -- Actual measurement (optional; read-only value). probably always there, if no text in code 1
2.885000000006151
...
100
AcDbAlignedDimension
...
 13 -- defines the start point of reference line: from where we measure. it is also the start point for the first extension line
-8.714999375716946
 23
18.65497213215147
 33
0.0
 14 -- defines the end point of reference line: to where we measure. it is also the start point for the second extension line
-5.829999375710795
 24
18.65497213215147
 34
0.0
...



#Transform for SketchUp:
# DXF codes indicated in variables staring with p (point) or v(vector) or c(any code):

# variable assignment for later sketchup commands

# dimension line start point
p10 = "-5.829999375710795m".to_l
p20 = "19.10976678735829m".to_l
p30 = "0.0m".to_l
# Text center point
p11 = "-6.101444903469229m".to_l
p21 = "19.18676678843117m".to_l
p31 = "0.0m".to_l
# reference start point
p13 = "-8.714999375716946m".to_l
p23 = "18.65497213215147m".to_l
p33 = "0.0m".to_l
# reference end point
p14 = "-5.829999375710795m".to_l
p24 = "18.65497213215147m".to_l
p34 = "0.0m".to_l
# dimension type
c70 = 161
# user text
c1 = "<>"
# attachment point
c71 = 5
# actual measurement
c42 = "2.885000000006151m".to_l
# roatation angle, present if dimension type is 0
c50 = 0 # not present here




# create sketchup dimensions based on the above done variable assignment:

# dimension type:
dt = c70 - 128 if c70 >= 128
dt = dt - 64 if dt >= 64
dt = dt - 32 if dt >= 32

# we support only rotated/horizontal/vertical and aligned dimensions
if dt == 0 or dt == 1 then 


p0 = Geom::Point3d.new(p10, p20, p30)
p1 = Geom::Point3d.new(p11, p21, p31)
p3 = Geom::Point3d.new(p13, p23, p33)
p4 = Geom::Point3d.new(p14, p24, p34)

v0 = Geom::Vector3d.new(p0.to_a)
v1 = Geom::Vector3d.new(p1.to_a)
v3 = Geom::Vector3d.new(p3.to_a)
v4 = Geom::Vector3d.new(p4.to_a)

entities = Sketchup.active_model.entities

# draw aligned linear dimension
dim = entities.add_dimension_linear p4, p3, v0 - v4
dim.has_aligned_text = true # set text aligned to dimension line, not screen orientation

# Text
=begin
As the user text is stored as MTEXT under a dbBlock reference (code 2), it is difficult to get the text. 
Therefor either put a space or let Sketchup calculate. I would display the user text as defined in Code 1 and if empty or <> in dxf, put a space.
But still let the MTEXT dimension value be imported.
Alternative is to search the MTEXT value linked to the dimension via the block reference (code 2) and put that text into the sketchup dim text. 
But as the sketchup text formatting is lmited, I would not do it.
=end
case 
  when c1 == "<>" then t = c42.to_s
  when c1.empty? then t = " " 
  else t = c1
end 
dim.text = t

#Text position:
=begin
Figure out the Sketchup text position is either
Sketchup::DimensionLinear::TEXT_OUTSIDE_START
Sketchup::DimensionLinear::TEXT_CENTERED
Sketchup::DimensionLinear::TEXT_OUTSIDE_END
Checking where the text center Code (11, 21, 31) is in relation to the reference line.
use a vector v40pn perpendicuar to the extension line (v0 - v4) x ((v0 - v4) x (v4 - v3)), normalize it, then scale it to length |v4 - v3| along this direction
Calculate the scalar (dot) prodcut of tsp = v40pn.normalized * (v1 - v0)
if the scalar vector product of (sp  > |v3 - v4| then TEXT_OUTSIDE_START else if sp < 0 then TEXT_OUTSIDE_END else TEXT_CENTERED
=end


v40pn = ((v0 - v4).cross((v4 - v3).cross(v0 - v4))).normalize
v40p_len34 = v40pn.dot(v4 - v3)

# make sure the vector points into positive x direction (writing direction is from left to right). If not, then swap the result

tsp = v40pn.dot(v1 - v0)
if 
  # when t == " " then tpos = Sketchup::DimensionLinear::TEXT_OUTSIDE_START # if no text, then put space at the beginning, so there is no gap in the dimension line
    tsp > 0 and v40pn.x >= 0 then 
       tpos = Sketchup::DimensionLinear::TEXT_OUTSIDE_START
   elsif tsp > 0 and v40pn.x < 0 then 
      tpos = Sketchup::DimensionLinear::TEXT_OUTSIDE_END
   elsif tsp < -v40p_len34 and v40pn.x >= 0 then 
      tpos = Sketchup::DimensionLinear::TEXT_OUTSIDE_END
   elsif tsp < -v40p_len34 and v40pn.x < 0 then 
      tpos = Sketchup::DimensionLinear::TEXT_OUTSIDE_START
   else tpos = Sketchup::DimensionLinear::TEXT_CENTERED
end
dim.text_position = tpos


# Aligned position, if centerd text
=begin
If center, then decide if in Sketchup above, on line or outside (not between reference and dimension line):
Sketchup::DimensionLinear::ALIGNED_TEXT_ABOVE
Sketchup::DimensionLinear::ALIGNED_TEXT_CENTER
Sketchup::DimensionLinear::ALIGNED_TEXT_OUTSIDE
Check if the scalar (dot) vector product of
([10,20,30]-[14,24,34] ) * ( [11, 21, 31]-[10,20,30] ) is positive (then outside), if 0 (then centered), otherwise above.
set the value even if the text is not centered, as the user might change to centered and then the aligned position is already as in dxf.
=end

asp = (v0 - v4).dot(v1 - v0)
case 
  when asp > 0 then tapos = Sketchup::DimensionLinear::ALIGNED_TEXT_OUTSIDE
  when asp == 0 then tapos = Sketchup::DimensionLinear::ALIGNED_TEXT_CENTER
  else tapos = Sketchup::DimensionLinear::ALIGNED_TEXT_ABOVE
end
dim.aligned_text_position = tapos


# Text font: 
=begin
 if TIG does not read the dimension text font already, use sketchup dimension default font.
 Ideal would be, that the font is changed from Pixels to height, so that the dimension zooms lke the 3Dtext
=end


# Arrow heads: 
=begin
As the arrow heads are also defined via the block ref (in code 2) and this might be difficult to interpret, 
Just use Sketchup default arrow head style. User can still easily change the style later for all dimensions at once.
=end

end