GIS-based Design of Dynamic Simulation System on Urban Municipal and Public Facilities

ssing results.

Keywords: GIS, Municipal and public facilities, Dynamic simulation.

1 INTRODUCTION

so that the planner and designer can easily find, modify and adjust all facilities that are not suitable for the current land capacity, and then define the improving strategies according to repeating optimization results.

2 SYSTEM FUNCTIONS

(1) The Overall Functions of System

1) Storing and managing

2) Query and retrieving

3) Forecasting urban requirements for underground infrastructure

4) Analyzing actuality information

5) Optimizing targets

6) Dynamic simulation

(2) Functions of Subsystems

1) Water subsystem

2) Sewer(or wastewater) subsystem

3) Rainwater subsystem

4) Power subsystem

5) Post and telecommunication subsystem

6) Gas subsystem

7) Heating subsystem

3 DATA ORGANIZATION

(1) Classification and Hierarchy of Graphic Data

The urban topographic data for referenced positioning;
The actuality and planning graphic data of urban land utilization for designing;
The actuality and planning graphic data of urban loads for defining routes;
The graphic data of urban underground synthetical nets for designing;
The actuality and planning graphic data of urban water subsystem for designing, comparison, and optimization;
The actuality and planning graphic data of urban sewer subsystem for designing, comparison, and optimization;
The actuality and planning graphic data of urban rainwater subsystem for designing, comparison, and optimization;
The actuality and planning graphic data of urban power subsystem for designing, comparison, and optimization;
The actuality and planning graphic data of urban post and telecommunication subsystem for designing, comparison, and optimization;
The actuality and planning graphic data of urban gas subsystem for designing, comparison, and optimization;
The actuality and planning graphic data of urban heating subsystem for designing, comparison, and optimization;

(2) Organization of the Attributes

1) The attributes of arcs in rainwater subsystem

2) The attributes of nodes in rainwater subsystem

3) The attributes of points in rainwater subsystem

4) The attributes of polygons in rainwater subsystem

4 AN EXAMPLE OF THE SYSTEM FUNCTIONS

(1) Implementation of Algorithm

1) About the sewer subsystem

Internal ID of From- and To- node, Internal ID of Right- and Left- polygon(with dumb value), User ID, Internal ID, Length, Type, Level, Mean depth of embedment, Original discharge, Designed-discharge(to be computed), Gradient, etc.

2) Principles of recursive analysis model

Based upon the specific structure of sewer subsystem, we can employ the recursive algorithm for fast calculation of the designed-discharge. Before recursive processing, a chained list which is the base of recursion in our model must be established and initialized. It is, in fact, another description of the relationship between the arcs(pipes) and nodes(manholes) other than that in AAT for consideration of efficiency and convenience of recursive algorithm. We define nine items in the chained Index: Serial number of tuples numbered in order of being read from AAT;
ID: Internal ID of the considered pipe;
FN: From- node ID of the considered pipe;
TN: To- node ID of the considered pipe;
Qori: Original discharge of the considered pipe;
F_index: Index of the father pipe of the considered pipe; father means the downstream pipe adjacent to the considered pipe;
C_number: Number of the children pipes of the considered pipe; here, child means the upstream pipe adjacent to the considered pipe;
Finished: Mark indicating whether the designed-discharge of the considered pipe has been computed completely;
Qdsn: Designed-discharge of the considered pipe.
where the values of ID, FN, TN, Qori of each pipe are extracted directly from the AAT.

For a sewer subsystem with n pipes, for example, the steps of the initialization include:

Step 1: inserting a virtual tuple into the chained list as the first tuple. The virtual tuple in this step means the tuple with 0 value in each item. The pipe corresponding to the virtual tuple is then called the virtual pipe and can be seen as the father pipe of those pipes whose To- nodes each are a root of corresponding tree. Based upon the virtual concept, the sewer subsystem can be further abstracted as a full tree other than a forest. The designed-discharge of the virtual pipe is ther Step 2: filling in ID, FN, TN, and Qori of the chained list as the following manner£º
for i=1 to n step 1
{reading a tuple from AAT in sequence;
filling in ID(i), FN(i), TN(i), and Qori(i) with corresponding data extracted from the tuple, respectively.}
Note that the reading process must be in sequence and the necessary data will be located in the chained list properly after cycling.

Step 3: initializing the Qdsn, F_index, C_number, and Finished, respectively.
for i=1 to n step 1
{ Qdsn(i)=Qori(i);
F_index(i)=C_number(i)=Finished(i)=0. }

Step 4: searching the roots of original trees and linking them with the virtual pipe. Then we have
for i=1 to n step 1
for j=1 to n step 1
if TN(i)=FN(j) then TN(i)=0.

Step 5: calculating the F_index and C_number of each pipe. We have
for i=1 to n step 1
for j=0 to n step 1
if TN(i)=FN(j) then F_index(i)=j, C_number(j)=C_number(j)+1.

The recursive algorithm includes two procedures i.e. the main invocation and the recursive invocation. The main invocation is a cycle procedure taking the following form:

main invocation(main-program)
for i=1 to n step 1
if C_number(i)=0 and Finished(i)=0 then recursion(i).

The recursive invocation for i-th tuple is:

recursive invocation(recursion(i))
Finished(i)=1;
F_index_tmp = F_index(i);
Qdsn(F_index_tmp)=Qdsn(F_index_tmp)+Qdsn(i);
C_number(F_index_tmp)=C_number(F_index_tmp)-1;
if C_number(F_index_tmp)=0 then recursion(F_index_tmp)
else return to last recursion or main-program.
where, 1<= i <=n.

The main invocation scans the tuples in the chained list in turn, and searches the tuples satisfying the recursive conditions. The variable C_number(i), for example, changes with the recursive invocation. The variable Finished(i) indicates whether Qdsn(i) has been calculated. That both C_number(i) and Finished(i) are zero denotes that the Qdsn(i) is already known and can be used to calculate the designed-discharge of downstream pipes of ID(i)-th pipe by invoking the recursion(i). A positive Note that the recursion is in fact an action of adding the current pipe's designed-discharge(i.e. Qdsn(i)) to its father pipe's designed-discharge (Qdsn(F_index_tmp)). The children number of its father pipe (i.e. C_number(F_index_tmp)) decreases after each action. If the children number becomes zero, then the father pipe will be as the current pipe and repeat the recursive processing. And so on. The recursion(i) will not end until a downstream pipe (i.e. the father, or the grandfather, and

(2) Dynamic Simulation

5 CONCLUSION

REFERENCES

Meng Lingkui and Bian Fuling. GIS-based Designed-discharge Analysis Model for Urban Sewer System. Proceedings of Geoinformatics'96 Wuhan, China, 1996, 2, 112-117.

Meng Lingkui and Bian Fuling, Integration of Geographic Information Systems. Proceedings of Geoinformatics'96 Wuhan, China, 1996, 1, 302-307.

Shea C, Grayman W, and Darden D. Integrated GIS and Hydrologic Modeling for Countywide Drainage Study. Journal of Water Resources Planning and Management, 1993, 119(2): 112-128.

Wei Du. GIS Supported Metropolitan Sewer System Modeling and Urban Environment Planning. Proceedings of Geoinformatics'95 Hong Kong, 1995, 2: 738-745.