Sherry,
To expand on Autocad DXF files, two forms of DXF file can be created from
Autocad.
1. The Complete Autocad drawing DXF file
2. An "Entities Only" DXF file
You can think of an Autocad drawing as a workspace with multiple views that
has all the objects ("Entities") saved within the drawing. Rather than
stored in separate .tab files, entities are organised into a series of
layers within the Autocad drawing.
No. 1 will contain a large "Heading" section including details such as the
extents of the drawing, the coordinate system, the layer structure,,
"Blocks" (a DIY symbol), a whole bundle of setup information- oh- at the
end, you get a list of the "entities" .
No. 2 is only this last section.
Simplistically, it's not clear why the "Heading" section is required: all
Mapinfo needs, surely, is the entities. You already have to tell Mapinfo
the coordinate system used; the "Blocks" will be minced in either case
(explode them in Autocad first !), the rest of the information is (at least
for my purposes) irrelevant. Layer information is attached to each
object.in the "Entities" section.
However, from your error message ("All objects will be considered to be on
layer 0"), it 's clear that Mapinfo needs the "Layers" section of the DXF
Header to set up the Table Import. (It is possible to select individual
tables to import or even to create separate .tab files from different
Autocad layers within the one DXF file. )
FYI. Layer 0 is the "standard" Autocad layer, it's always there, like
Mapinfo's cosmetic layer (only in Autocad, layer 0 behaves itself). It
would make sense to write a DXF import filter that assumed everything was
on layer 0 if no other information was available.
To check your DXF file has some entities in it, run it through a good text
editor (the files tend to be too big for some). At the end you should have
something that looks like :-
0
SECTION
0
ENTITIES
0
LINE (or some other type of Entity)
0
6
followed by some coodinates then:-
0
ENDSEC
0
EOF
I hope this helps you to understand your problem a little better. Good
Luck.
Brian Forrester
Mapping Analyst
Wood Mackenzie
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