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Page Title:
Table 59. Format for spatial index (*.*SI) file. |
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|  MIL-D-89009
m. Spatial index. A spatial index file is implemented for
each face, edge, entity node and text primitive table in
a tile directory. A spatial index provides the
capability to use a set of coordinates to identify a
primitive, and its associated feature attributes. The
DCW implements spatial query indices for reduction of
data access time for geographic coordinate queries of
the DCW database.
The spatial indices are contained within files using one
of four suffixes in their filename: FSI (Face Spatial
Index), ESI (Edge Spatial Index), NSI (Node Spatial
Index), and TSI (Text Spatial Index). The VPF spatial
index (TABLE 59) is a sequential file of data that is
partitioned into three groups:
(1)
A header containing the number of primitives, the
bounding rectangle of the spatial extent of the
tile, and the number of nodes in a binary search
tree.
(2)
A bit array of the tree where each bit represents
the tree node id.
(3)
Each tree node written as a record.
TABLE 59.
Format for spatial index (*.*SI) file.
Starting
No.
Position
of
Field
(Bytes)
Bytes
Type
Description
0
4
Integer
Number of primitives
4
4
Float
Bounding rectangle x1
8
4
Float
Bounding rectangle y1
12
4
Float
Bounding rectangle x2
16
4
Float
Bounding rectangle y2
20
4
Integer
Number of nodes in tree
24 + n * 4
4
Integer
Offset (os) of primitive list for
node n
24 + n * 4 + 4
4
Integer
Count in integer units
os+(8*NNODE+24)+c*8
1
Byte
Primitive bounding rectangle x1
+0
os+(8*NNODE+24)+c*8
1
Byte
Primitive bounding rectangle y1
+1
os+(8*NNODE+24)+c*8
1
Byte
Primitive bounding rectangle x2
+2
os+(8*NNODE+24)+c*8
1
Byte
Primitive bounding rectangle y2
+3
os+(8*NNODE+24)+c*8
4
Integer
Primitive ID
+4
54
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