International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
3. To explain the feasibility and performance of the
proposed integrated system, using simulated and real data.
So, an integrated photogrammetric CAD-based system has
designed and implemented, which can overcome most of
deficiencies of existing integrated systems. Using existing
(available) standard photogrammetric instruments and CAD
systems, the operation design of this new integrated system is
prepared. According to the operational design, required
softwares are developed and finally designed system is
completely tested on sample data and real digital data. After
testing the operation of designed system, output data is exported
to GIS environments successfully.
1.2 Organization of the Dissertation
In the following chapters, at first we'll explain IPCBS software,
which is designed and implemented at the Geodesy and
Geomatics Engineering Department of Khaje-Nasir-Toosi
technical university. IPCBS is a powerful On-line CAD Based
Photogrammetric system, which eliminates geometric and
topologic errors, exactly at the same time of object digitizing.
New real-time data cleanup method which is invented for
IPCBS will be described in next chapter. In chapter 4,
successful test of IPCBS on real data and its efficiency will be
explained. We'll have a detail conclusion on subject of this
research and then we will recommend future exploration that
should be performed to improve data extraction ways in
Photogrammetry, especially using integrated systems in the final
chapter.
2. REAL-TIME PRODUCING OF GIS-READY DATA
2.1 IPCBS and Its Necessity
Extracting data and drawing maps by photogrammetric or
integrated instruments often take long time. Raw output data
should be edited to become usable for cartographic purposes
and other applications (i.e. GIS). Therefore, there is a need for
supplementary software to omit or modify the editing phase. If
edit-step could be done exactly in time of object drawing then
plenty of cost and time will be saved. This is our target.
For this purpose a program called "Integrated Photogrammetric
CAD-Based System", IPCBS has been written. This program is
run on a computer which is connected to a PlaniComp
analytical stereoplotter with MicroStation V5 platform as CAD
system, under Microsoft Windows or MS-DOS operating
system. IPCBS's output data are in DGN format, that can be
easily imported to GIS systems (i.e. ArcInfo, LaserScan, Caris,
...) to be analysed, without need to any post-processing
procedure.
2.2 Conceptual Model/Design of IPCBS
In IPCBS, PlaniComp P33's photogrammetric tools are
embedded within MicroStation, thus with this system many
modification (i.e. data cleanup) can be performed on objects
and some topological relationships can be assigned to objects
before inputting data to CAD kernel. According to this
specification, the conceptual model is as follows:
l. PlaniComp P33 sends raw data to computer. When
user digitizes by P-Cursor, PlaniComp's encoders
convert these motions to electric signals and send
these raw data to computer [Carl Zeiss Division of
Photogrammetry, 1993].
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2. These data is received through I/O port of computer
and CAD program gets them as input.
3. Supplementary program (IPCBS) which is loaded in
CAD program gets raw data and processes it. Data
will change according to predefined cleanup rules.
4. TPCBS sends refined data to CAD database and
features will be drawn in DGN file.
Final DGN file can be imported in any GIS software
without any post-processing.
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2.3 Technical Specification of IPCBS
First version of IPCBS is written in MDL version 5. MDL is
MicroStation Development Language, which is a complete
development environment that lets applications take full
advantage of the power of the MicroStation’s CAD engine.
With MDL, we developed tightly integrated interactive
application that run inside MicroStation. The user-friendly
interface of IPCBS application gets required information (i.e.
tolerance values and level settings, ...) from user. This
application can be easily ported between hardware platforms.
PCAP interface program of P33 analytical plotter should be
residence in the memory, just after start of MicroStation. After
that IPCBS program should be loaded and be residence in the
memory [Carl Zeiss Division of Photogrammetry, 1994]. The
IPCBS is an EVENT-driven program. An event may be any
user input, for example when user sends keystroke or clicks
buttons of mouse or tablet (P-Cursor) to send a datapoint or
reset or even when user moves the tablet (P-Cursor) or mouse
an event occurs and dynamically changes. All events input to
MicroStation are gathered by the input handlers and put in the
input queue. When the event reaches the head of the queue, the
task ID dispatcher processes it. The dispatcher sends the event
to the appropriate application for fully processing the event.
Then PCAP interface will interpret the received data and
convert it to another data, which is readable and acceptable for
MicroStation. Now, IPCBS will take all the system under its
control. IPCBS will get EVENT data from PCAP and compile it
according to active command requirement.
After all, a customized command which is activated and needed
arguments for running can start its work. For example, “phLStr”
is a customized command, which is defined in IPCBS program,
for drawing a new LineString, using P-Cursor's datapoints.
Setting of level, color, style, weight and class will be according
to IPCBS user settings. It works according to the following
steps:
1. Performing initial photogrammetric tasks, which are
orientations (interior, relative and absolute) and
configuring the system settings using PCAP program;
2. Starting MicroStation and loading P33 interface
program. MicroStation now is configured and
recognizes P33 as an input/output device;
3. When user moves P-Cursor or sends a datapoint or
reset by P-Cursor, PCAP’s 1/O interrupt handling
module can sense and interpret it (MicroStation
always would be suspicious for P-Cursor events while
is running);
4. Next step is loading IPCBS program. This program
will be resident in memory and suspicious for PCAP
events (what PCAP interprets from status of P-
Cursor);
5. IPCBS's customized commands can be entered by
keyboard or user interface menu;
6. IPCBS's event handling function makes a decision on
event, which is received from PCAP event handling
function. If user input was ‘Reset’, then control will
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