ex for a com-
x information
iry shape that
object's index
Its at the 2nd
personal com-
that most of
especially the
This implies
ck interactive
dex
ism quite dif-
lowing advan-
;the structure
'e efficient;
vith irregular
ind the query
For instance,
1eters along a
lant areas be-
e (refer to fig-
00 10000
ects | objects
40 9. 20
50 4. 70
14 0. 18
38 | 595. 40
52 1. 95
44 7.29
16 0.19
n second)
—— 20m
——-200m
region query
(4) Can control query precision level. Different
applications require different precisions. For ex-
ample, in a military GIS system, accurate results
are often needed ;In an interactive tour information
system , user can give a query condition on a touch
screen with his or her finger. In this case, the
query precision level at the first or second level is
enough, therefore further computation is omitted,
so the performance is improved.
6 Conclusions
Ladex is a new spatial index mechanism, it sup-
ports index of spatial objects in irregular shape,
and can control query precision level. The struc-
ture is simple. The fundamental algorithms are of
high performance. We integrated Ladex with B"-
tree to improve the efficiency of spatial retrieval.
In our Map Database Management System MDB,
Ladex has changed the query format significantly.
Users do not need to master complex SQL
database language, they can use mouse to select
objects or draw a query range in arbitrary shape on
the screen, and immediately get the information of
the desired objects. If users operate through touch
screen, they can get what they want with their fin-
gers. This is really " What you want, what you
get" without any ad hoc language.
Future work could focus on: (1) In application,
find an approach to determine the optimal number
of the first level blocks; (2) Study the relationship
between the number of partition levels and spatial
search efficiency; (3)Find a better way to expres
feature information; (4) Extend Ladex mechanism
to 3 and above dimensional space.
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