arc-info binary coverage files format.htm

ArcInfo Binary Coverage Files Format

  <P>Note that PC Coverages files are ALWAYS single precision. 
  <P>
  <H3><A name=ARC_PC2>2.3.3 ARC file in PC Coverages V2</A></H3>
  <P>Identical to V7.x 
  <P>
  <P>
  <H3><A name=ARC_WEIRD>2.3.4 ARC file in Weird Coverages</A></H3>
  <P>Same as V7 Coverages, except that the main file is called "ARC" and the 
  index "ARX". </P></UL>
<P>
<H3><A name=PAL>2.4 PAL.ADF</A></H3>
<P>
<UL>The "pal.adf" file contains the polygon definitions. It is present only 
  inside coverages with clean polygon topology. 
  <P>It comes with an <A 
  href="http://avce00.maptools.org/docs/v7_bin_cover.html#Index">index file</A> 
  called "pax.adf". 
  <P>
  <H3><A name=PAL_V7>2.4.1 PAL.ADF file in V7.x Coverages</A></H3>
  <P>The file starts with the usual 100 bytes header: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Signature - 9994
	4-7	int32	Precision - +11 for single precision, 
	                            and -11 or 1011 (yep!) for double prec.
	8-11	int32	Record size (always 0: variable length records)
	12-23		All zeros
	24-27	int32	File size (in 2 byte words), including header size 
	28-99		All zeros
</PRE>
  <P>Then variable length polygon records follow: 
  <P>For SINGLE PRECISION: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Polygon Id
	4-7	int32	Record Length, number of 2 byte words that follow
                        the current value.
	8-11	float	Min. X coordinate
	12-15	float	Min. Y coordinate
	16-19	float	Max. X coordinate
	20-23	float	Max. Y coordinate
	24-27	int32	Number of Arcs
	28+     int32	List of Arc records (see below)
</PRE>
  <P>For DOUBLE PRECISION: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Polygon Id
	4-7	int32	Record Length, number of 2 byte words that follow
                        the current value.
	8-15	double	Min. X coordinate
	16-23	double	Min. Y coordinate
	24-31	double	Max. X coordinate
	32-39	double	Max. Y coordinate
	40-43	int32	Number of Arcs
	24+     int32	List of Arc records (see below)
</PRE>
  <P>For each arc in the arc list, we have a fixed length record: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Arc_Id
	4-7	int32	From_Node_Id
	8-11	int32	Adjacent_Polygon_Id
</PRE>
  <P>
  <UL>
    <LI>Arc_Id will be negative if the direction of the arc is reversed 
    <LI>From_Node_Id is the arc's FNODE#. If the arc is reversed, then 
    From_Node_Id will be the arc's TNODE#. 
    <LI>Adjacent_Polygon_Id is the Id of the polygon that shares this arc with 
    the current polygon. </LI></UL>
  <P>
  <H3><A name=PAL_PC>2.4.2 PAL file in PC Coverages V1</A></H3>
  <P>In PC Coverages, the main file is called "PAL" and the index "PAX". 
  <P>They both start with the <A 
  href="http://avce00.maptools.org/docs/v7_bin_cover.html#Header_PC">256 bytes 
  header</A> specific to PC Coverages, followed by the 100 bytes header and the 
  data records as described above. 
  <P>Note that PC Coverages files are ALWAYS single precision. 
  <P>
  <H3><A name=PAL_WEIRD>2.4.3 PAL file in Weird Coverages</A></H3>
  <P>Same as V7 Coverages, except that the main file is called "PAL" and the 
  index "PAX". </P></UL>
<P>
<H3><A name=LAB>2.5 LAB.ADF</A></H3>
<P>
<UL>The "lab.adf" file contains label point records. 
  <P>This file has no associated index since it has fixed size records. 
  <P>
  <H3><A name=LAB_V7>2.5.1 LAB.ADF file in V7.x Coverages</A></H3>
  <P>The file starts with the usual 100 bytes header: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Signature - 9993
	4-7	int32	Precision - +2 for single precision, 
	                            and -2 for double precision.
	8-11	int32	Label Record size, in 2 byte words 
	                    (16 for single prec. and 28 for double prec.)
	12-23		All zeros
	24-27	int32	File size (in 2 byte words), including header size 
	28-99		All zeros
</PRE>
  <P>Then fixed size label point records follow: 
  <P>For SINGLE PRECISION: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Label Value
	4-7	int32	Polygon_Id
	8-11	float	Label X coord.
	12-15	float	Label Y coord.
	16-19	float	Label X coord.
	20-23	float	Label Y coord.
	24-27	float	Label X coord.
	28-31	float	Label Y coord.
</PRE>
  <P>For DOUBLE PRECISION: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Label Value
	4-7	int32	Polygon_Id
	8-15	double	Label X coord.
	16-23	double	Label Y coord.
	24-31	double	Label X coord.
	32-39	double	Label Y coord.
	40-47	double	Label X coord.
	48-55	double	Label Y coord.
</PRE>
  <P>
  <H3><A name=LAB_PC>2.5.2 LAB file in PC Coverages V1</A></H3>
  <P>In PC Coverages, this file is called "LAB". 
  <P>It starts with the <A 
  href="http://avce00.maptools.org/docs/v7_bin_cover.html#Header_PC">256 bytes 
  header</A> specific to PC Coverages, followed by the 100 bytes header and the 
  data records as described above. 
  <P>Note that PC Coverages files are ALWAYS single precision. 
  <P>
  <H3><A name=LAB_WEIRD>2.5.3 LAB file in Weird Coverages</A></H3>
  <P>Same as V7 Coverages, except that the file is called "LAB". </P></UL>
<P>
<H3><A name=CNT>2.6 CNT.ADF</A></H3>
<P>
<UL>The "cnt.adf" file contains polygon centroid information. 
  <P>It comes with an <A 
  href="http://avce00.maptools.org/docs/v7_bin_cover.html#Index">index file</A> 
  called "cnx.adf". 
  <P>
  <H3><A name=CNT_V7>2.6.1 CNT.ADF file in V7.x Coverages</A></H3>
  <P>The file starts with the usual 100 bytes header: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Signature - 9994
	4-7	int32	Precision - +14 for single precision, 
	                            and -14 for double precision.
	8-11	int32	Record size (always 0: variable length records)
	12-23		All zeros
	24-27	int32	File size (in 2 byte words), including header size 
	28-99		All zeros
</PRE>
  <P>Then variable length centroid records follow: 
  <P>For SINGLE PRECISION: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Polygon Id
	4-7	int32	Record Length, number of 2 byte words that follow
                        the current value.
	8-11	float	Centroid X coordinate
	12-15	float	Centroid Y coordinate
	16-19	int32	Num_Labels ( &gt;= 0 )
	20+     int32	List of Label Ids (Only if Num_Labels &gt; 0 )
</PRE>
  <P>For DOUBLE PRECISION: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Polygon Id
	4-7	int32	Record Length, number of 2 byte words that follow
                        the current value.
	8-15	double	Centroid X coordinate
	16-23	double	Centroid Y coordinate
	24-27	int32	Num_Labels ( &gt;= 0 )
	28+     int32	List of Label Ids (Only if Num_Labels &gt; 0 ) 
</PRE>
  <P>
  <H3><A name=CNT_PC>2.6.2 CNT file in PC Coverages V1</A></H3>
  <P>In PC Coverages, the main file is called "CNT" and the index "CNX". 
  <P>They both start with the <A 
  href="http://avce00.maptools.org/docs/v7_bin_cover.html#Header_PC">256 bytes 
  header</A> specific to PC Coverages, followed by the 100 bytes header and the 
  data records as described above. 
  <P>Note that PC Coverages files are ALWAYS single precision. 
  <P>
  <H3><A name=CNT_WEIRD>2.6.3 CNT file in Weird Coverages</A></H3>
  <P>Same as V7 Coverages, except that the main file is called "CNT" and the 
  index "CNX". </P></UL>
<P>
<H3><A name=PRJ>2.7 PRJ.ADF - Projection file</A></H3>
<P>
<UL>
  <P>
  <H3><A name=PRJ_V7>2.7.1 PRJ.ADF file in V7.x Coverages</A></H3>
  <P>The PRJ.ADF file is a simple ASCII file with one line for each piece of 
  projection information. The lines have a variable length and are terminated by 
  a newline character. 
  <P>Here is an example of a prj.adf file: <PRE>     Projection    GEOGRAPHIC
     Zunits        NO
     Units         DD
     Spheroid      CLARKE1866
     Xshift        0.0000000000
     Yshift        0.0000000000
     Parameters
</PRE>
  <P>
  <H3><A name=PRJ_PC>2.7.2 PRJ file in PC Coverages V1</A></H3>
  <P>PC Coverages do not appear to carry a PRJ file... or at least we never 
  encountered any. 
  <P>
  <H3><A name=PRJ_WEIRD>2.7.3 PRJ file in Weird Coverages</A></H3>
  <P>Just like for PC Coverages... they do not appear to carry a PRJ file... or 
  at least we never encountered any. </P></UL>
<P>
<H3><A name=LOG>2.8 LOG - Coverage history</A></H3>
<P>
<UL>
  <P>
  <H3><A name=LOG_V7>2.8.1 LOG file in V7.x Coverages</A></H3>
  <P>The LOG file (named "log", not "log.adf"!) is an ASCII file with variable 
  length lines each terminated with a newline. 
  <P>The lines have no known length limit, they can be longer than 80 characters 
  for sure. 
  <P>
  <H3><A name=LOG_PC>2.8.2 LOG file in PC Coverages V1</A></H3>
  <P>Nothing special... the file is called LOG as well. 
  <P>
  <H3><A name=LOG_WEIRD>2.8.3 LOG file in Weird Coverages</A></H3>
  <P>Probably the same... but we've never encountered any. </P></UL>
<P>
<H3><A name=TOL>2.9 TOL - Coverage Tolerances</A></H3>
<P>
<UL>
  <P>
  <H3><A name=TOL_V7>2.9.1 TOL.ADF file in V7.x Coverages</A></H3>
  <P>The TOL file contains the tolerance values to use when processing a polygon 
  coverage. It usually contains 10 tolerance entries. For each entry, we have a 
  tolerance type, a tolerance status, and a tolerance value. The tolerance types 
  are: 
  <P>
  <UL>
    <LI>1. fuzzy 
    <LI>2. generalize (unused) 
    <LI>3. node match (unused) 
    <LI>4. dangle 
    <LI>5. tic match 
    <LI>6. undefined 
    <LI>7. undefined 
    <LI>8. undefined 
    <LI>9. undefined 
    <LI>10. undefined </LI></UL>
  <P>The tolerance status "is set to 1 if the tolerance is verified (been 
  applied to operations of the coverage) and to 2 if the tolerance is not 
  verified (been set by the TOLERANCE command, but not yet used in processing)." 

  <P>In a SINGLE PRECISION coverage, the file is named "tol.adf", it has no 
  header, and for each tolerance value, we have: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Tolerance type (usually goes from 1 to 10)
	4-7	int32	Tolerance status
	8-11	float	Tolerance value
</PRE>
  <P>In DOUBLE PRECISION coverages, the file is named "par.adf", and it DOES 
  have the usual 100 bytes header: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Signature - Always 9993
	4-7	int32	Value of 40 (this should be the precision field???)
	8-11	int32	Tolerance record size, in 2 byte words (always 8)
	12-23		All zeros
	24-27	int32	File size (in 2 byte words), including header size 
	28-99		All zeros
</PRE>
  <P>Then for each double precision tolerance value, we have: 
  <P><PRE>	Bytes	Type	Description

	0-3	int32	Tolerance type (usually goes from 1 to 10)
	4-7	int32	Tolerance status
	8-15	double	Tolerance value