CCTV
Focus (Russian edition) #5-2004
Professional
design of CCTV systems
During
the design of CCTV systems much time is spent on estimating
lens focal length and the right location of video cameras
to get the necessary image on the screen.
Estimating person identification areas and license plate
reading areas causes additional difficulties for a designer.
The task becomes more complicated when it is necessary
to choose optimal relative positions of several cameras
or when it is necessary to make one camera solve several
tasks (for example identification of entering people and
surveillance over the perimeter). You can also add the
necessity to calculate how this or that object will be
displayed, where the motion detector will detect a person
for an instance with enough light and contrast ratio,
and where it will not.
Not
only lens focal length but also the height of the camera
installation, maximum distance and the height of surveillance
have an influence on the screen image. Choosing the wrong
camera location and the wrong height of camera installation,
even with the replacement of the lens, wouldn’t be
able to provide you with the desired image!
If we also remember obstacles that distort the viewing
areas and dead space under the camera, then we can see
the difficulty of the problem. The more difficult the
task is the more likely that a mistake will occur. The
result of which at best can be a project cost increase.
These tasks can be solved in different ways.
Someone accurately calculates the viewing areas for several
heights and lens focal length of each camera using self
deducted formulas or formulas taken from guide books and
then transfers or combines obtained templates.
Someone makes the calculation easier and having introduced
reserves gets approximate results with the help of a Lens
calculator.
Someone draws on the plans only the horizontal angles
from lens specifications thus confusing himself and the
customer even more.
And many people ignore such calculations because of their
complexity and labour-intensiveness and place wide-angle
lenses or the most expensive ones (from the price list
of the producer).
A
CCTV project that doesn’t show the viewing areas
of each camera and their functions in different regions
of space cannot be considered a professional one.
Wide-angle
lenses (very often they remain the same even after acceptance
of work) as a rule satisfy the needs of a customer only
up to the first emergency. After an emergency it comes
out that there is practically no use for the installed
CCTV system. Criminal is not identified, license plate
is not read out, motion detector did not detect any movement.
It becomes obvious that there should be more cameras,
their locations should be different and lenses should
have other focal lengths.
The
situation looks different if professionally (well) executed
CCTV projects participate in a tender. Using a professional
CCTV project it is possible to discuss with a customer
a task for each camera, and to choose and substantiate
the necessary number. After doing the calculations more
video cameras may not be needed as one camera can fulfill
several tasks. Such solutions are more time consuming
but create effective and at the same time economical projects.
After each discussion and transference and when camera
parameters change one has to recalculate and compare several
variants of cameras placement. Thus professional designing
of a television system is a very difficult task that demands
much time.
Not all customers understand this and they give preference
not to the best project, but to the one that was quickly
rendered or to the cheapest one.
All
dependences of camera viewing areas obey the laws of geometrical
optics and can be described mathematically.
Widely spread are Lens Calculators that can be used on
many security web sites on-line. They can be in the form
of small programs or a plastic circle. Viewing areas are
viewed as a rule in the two-dimensional aspect which allows
the use of relatively easy calculations.
Calculators’ resources are approximately the same
but they are insufficient for professional designing.
The most convenient is the plastic circle which can be
easily used in field conditions. Calculators are convenient
for rapid calculations of viewing field width and height,
but they don’t allow calculating even the dead space
under the video camera let alone full-fledged calculation
of viewing areas’ projections to draw them on the
plan. This makes calculation of person identification
areas and license plate reading areas out of the question.
Moving
to a three dimension coordinate system the complexity
of calculations increases many times, and it is practically
impossible to find a good three-dimensional free calculator.
But it is still inconvenient to work with a specialized
three-dimensional calculator especially when it is necessary
to calculate several connected video cameras. One has
to simultaneously use a program-calculator and CAD program,
that locates video cameras on the plan, while recalculating
and redrawing viewing areas projections in order to get
the necessary result.
The next step is the integration of a three-dimension
calculator and CAD program. The calculator acquires a
graphical interface and its calculation results are presented
in graphic form. Obtained graphical calculation results
are represented directly on the plan of an object in horizontal
and vertical projections.
Graphical interface that allows locating video cameras
by one mouse click, to raise or lower a video camera only
by one turn of a mouse wheel, change its angle of inclination
and lens focal length and see the result there and then,
makes CCTV systems designing easy and exciting work. Completed
projects have the maximum of exactness, are quick to implement
and correct and don’t demand from a CCTV systems
designer mathematical knowledge and understanding of peculiarities
of objects’ representation in different parts of
viewing areas (although such understanding remains rather
useful).
These
and very many other ideas are realized in full measure
in a new program intended for CCTV systems designing.
This program is called VideoCAD. The latest version of
VideoCAD 5.0 is a full value CAD program integrated with
a special three-dimension calculator for calculating cameras’
viewing areas’ parameters. With the help of VideoCAD
one can design a CCTV project of any difficulty in a short
period of time. Specialized calculations of video surveillance
(viewing areas, person identification areas, license reading-out
areas, detailed representation of objects in different
parts of a viewing area, calculation of length and electrical
parameters of cables) are tightly integrated with traditional
CAD interface.
Let’s look briefly at an example of designing
a CCTV system with the help of VideoCAD.
1. Examining an object, discussing and formulating the
list of tasks stated before the CCTV system. Getting of
an object plan (better in electronic version, but also
acceptable on paper).
2. Object plan drawn on paper can be scanned and used
in VideoCAD as a background for cameras location. Electronic
object plan can be also used in VideoCAD (*.bmp, *.jpg,
*.jpeg, *.emf, *.wmf, *.dxf, *.dwg are supported).
3. Direct on the background with the help of VideoCAD
one can create preliminary camera locations.
4. During the next visit on the object preliminary cameras
location is corrected taking into account possible camera
locations, light, different obstacles, possibilities of
cables lay out, etc. Corrections of location are simple
and convenient in VideoCAD. All necessary actions are
conducted with several mouse clicks.
5. With the help of VideoCAD length and necessary parameters
of coaxial and power cables can be calculated. File containing
text with detailed descriptions of all video cameras and
cables is produced. On basis of obtained location with
marked viewing areas and also with the help of the text
file a business proposal is made.
6. Business proposal is sent to the customer for discussion
and concordance. During the discussion camera tasks and
their locations are specified after which with joint efforts
requirements specification is made. While making requirements
specification one can also use the text file. Especially
efficient is the discussion of a project in front of the
computer, as then it is easy to choose and total the required
number of cameras. It is obvious that after such a dialog
a competent customer will hardly move to a competitor.
7. In the process of designing all that is left, if necessary,
is to draw out the planning in VideoCAD, to make specifications,
explanatory notes, estimate calculations, etc. Your professional
project is ready!
8. While installing and adjusting, installers won’t
have to think about how to turn and to incline each camera.
In the project everything they need will be mentioned;
lens focal length, place and height of each camera, viewing
area. An installer will only need to turn the camera in
order to get the designated project viewing area.
9. While accepting the CCTV system, the customer makes
sure that all viewing areas agree with those marked in
the project. After estimating the quality of image and
installation work, he signs acceptance report.
10. After having accepted the system, all changes to viewing
areas should be charged extra.
Of
course the real sequence of actions can differ, but in
general one can see, that the process of designing a CCTV
system is getting clearer for both the designer and the
customer. The most important is the result one gets; an
efficient CCTV system that fulfills its functions in full
measure. Who knows how many crimes can be prevented and
uncovered with the help of it.
With
VideoCAD you can:
Choose
the most suitable lenses, heights and locations for camera
installation to provide the required parameters of view
areas, detect and identify a person, read license plates
and obtain an object image of required size on the screen
using the known actual sizes and location of the object.
Choose visually a relative location of cameras using the
graphics window with CAD interface.
Calculate the horizontal projection sizes of viewing,
person detecting, identifying and license plate reading
areas to draw them on the object plan.
Measure the view area distortions, arising from natural
obstacles.
Construct
three dimensional models of real scenes with the possibility
of loading prepared 3D models (a person, a car, etc.,
this library can be enlarged).
Obtain a model of a real image from each video camera.
This image can be printed and saved.
Model
quality parameters of a video image (resolution, compression,
coloration, smoothing, contrast, brightness).
Calculate the image size on the screen of any object in
camera view area in the percentage of screen size, pixels,
TV lines and millimeters (inches in case of Imperial format).
Model
multiscreen monitors and design operator interface using
the Monitors window.
Locate cameras and cables on the prepared layouts in *.bmp,
*.jpg, *.emf, *.wmf, *.dwg, *.dxf formats.
Obtain a drawing containing two projections of object
layout with the camera images, calculated view areas and
cables, and with coordinate grid and titles to be pasted
into graphical path of the project.
Print out the obtained drawing on one or several pages.It
is possible to use prepared frames with standard overlay
Title-Block and logo.
Export
the obtained drawing into any of the following formats:
*.bmp,*.emf, *.wmf, *.dxf (R14),*.dxf (R2000).
Calculate the Depth-of-field of each camera in the project.
Obtain a text file with full description of all the cameras
in the project, view areas and cables to be pasted into
a project explanatory note or used as an instruction for
installation.
Study
the influence of the criteria of person detection, identification
and license plate reading on the sizes and location of
the correspondent areas by changing the criteria according
to the video image quality.
Study the principles of object representation in different
view area parts using the test object and the graphics
window.
Calculate the length and electric parameters of cables.
Save expenses and win tenders due to the reduction of
cameras' quantity in projects and the increase of their
efficiency.
Reduce the time expended and boost the design quality.
Cut down the amount of controversial situations with customers
and accelerate their solution.
All
the calculations are real-time allowing to view the influence
of each parameter specified upon the final result.
VideoCAD does not use any simplified formulas and techniques,
in non-typical situations giving out considerable errors.
VideoCAD operates with any correct parameters, both selected
from the list or typed.
VideoCAD can be used for the prompt, but exact calculations
of the view area projections to draw on a location plan
when performing a graphical part of project. It can be
also used to perform a view area scrupulous analysis to
choose the most suitable camera location and lens parameters.
VideoCAD
can be effective at CCTV designer training.
Despite
its reach of opportunities VideoCAD is an inexpensive
program, available even for the general public. At present
VideoCAD is successfully used in many CCTV projects of
different scales.
