Far, Far Away…

One of the most frequently asked questions that we receive about our products is “How far can the camera see?” The answer to this question is not the same for every application, so the correct answer depends on who is asking the question.

In a highway traffic application, for example, the customer might want to know how far down the freeway the camera can look and display several lanes of traffic across the video image. In another type of vehicle tracking application, the customer might want to know at what distance the camera is able to resolve license plate numbers.

Let’s consider the highway traffic application first. The Interstate Highway System uses a standard lane width of 12 feet, so we will base our viewing distances on this figure. If we know what the horizontal field of view of the camera is at its maximum zoom setting, we can easily calculate at what distance the video image will show 1, 2, 3 or 4 lanes of traffic to the traffic engineer at the operations center. Here is a table showing the maximum viewing distances for cameras with several different zoom factors and horizontal field of view values:

Normally, a traffic engineer would be interested in the inbound traffic in the morning and the outbound traffic at night, so on an 8 lane major thoroughfare, we would use a 4 lane width for calculating the camera viewing distance. We can see from this table that if a traffic engineer was asking “How far can this camera see?”, the answer would probably be about 0.3 Miles for the camera with the x35 zoom capability. With this information, the engineer would be able to determine how far apart the cameras could be placed alongside the highway in order to have adequate coverage for good viewing quality. If these were pan, tilt and zoom cameras capable of looking in either direction down the highway, the cameras could be placed 0.6 miles apart.

Another vehicle related application that depends on knowing how far the camera can see is license plate recognition. Determining the maximum distance at which a license plate can be read is a little more complicated than the straight-forward calculation used in the previous highway application, though. The maximum usable distance in this application will depend on whether the intent is for an operator to be able to read the license plate or if the license plate is going to be read by an automated Optical Character Recognition (OCR), computer based system.

OCR license plate readers are highly sophisticated machine vision systems that usually use special cameras with built in high powered infrared LED strobe lights to enable optimum viewing in all lighting conditions. They also are typically used in situations where the vehicle position and orientation is carefully controlled, like a community guard gate or a toll booth lane. These types of systems usually are specified to operate at distances of about 10 feet to 40 feet.

In the case of conventional color cameras being viewed by an operator during daylight conditions, though (say on a street or highway), we can make some assumptions and come up with a ballpark figure as a guide for how close a vehicle must be for an operator to read the license plate. This might be a situation where a guard is monitoring an entire parking lot with a pan, tilt and zoom camera, and wants to zoom in on the vehicle entering the gate occasionally, and write down the license plate number. In the JPEG image below, which has a 512 x 384 pixel resolution, the vehicle fills up the middle third of the video image, and the license plate number is discernable under these relatively optimal lighting conditions. A resolution of 500 lines of resolution would be about the upper limit under ideal installation conditions for a high quality CCD camera.

The license plate actually encompasses about 81 x 43 pixels in this image. The image below shows the license plate section blown up in size to show the actual resolution of the license plate portion of the image.

As you can see, the license plate number, even at a resolution of only 45 x 23 pixels or so is still just barely discernable by a human operator under good lighting conditions (if you squint a bit). This would probably be the minimum resolution that would work. If we calculate the maximum vehicle distance using the same cameras as before and using the size of the license plate as a guide we get approximately the same results that we did for the one lane calculations.

Naturally this application depends on a lot of variables, like the lighting conditions, the quality and distance of the video cabling, the cleanliness of the license plate, the operator skill and other factors. These numbers are only a very rough guideline. Your results may vary.

So, when considering different applications, the answer to the question “How far can the camera see?” is, “it depends”.

~Dale Roche, Director of Engineering

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WTI (Wireless Technology, Inc.)

Video Surveillance Products Dedicated to the Broadcast, Global Security and Transportation Markets!

www.gotowti.com ● www.wirelesstech.com

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Keeping the Channel Islands Harbor safe – year after year!

WTI has worked with the Channel Island Harbor in Oxnard, California on many different projects over the past few years. Originally, a single P/T/Z camera was installed for basic viewing of the surrounding area as a beautiful shot to share with our customers to demonstrate the functionality of our P/T/Z cameras. The camera was situated so that anyone viewing the camera could watch sunrises and sunsets, the ocean waves crashing on the beach, and boats docking or leaving the harbor.

A few years after the installation of our demo camera, we decided that this location would be a great place to test more of our products. The next opportunity available to us was with our MACH I Ethernet/IP radio system. There were approximately 8 businesses in the general area that were requesting an internet connection for their offices, which we knew we would be able to provide wirelessly from our main headquarters. From a crow’s eye view, we were about 6.1 miles away from their head end; which was worrisome at first since wireless systems require line of site, but with proper mounting we were successful in our goals. With the link up and running and the businesses happy with their setup, we decided to branch out with that signal.

A local friend of the company, who also owned one of the businesses that was now receiving WTI internet services, was first to try home internet service using the MACH I system. His home was located approximately one mile away from our new head end. At his house, we mounted a patch antenna with another MACH I unit and faced it in the direction of the head end, and without a hitch he was up and running with a full speed internet connection in minutes. With this system up and working properly, we could now offer this service to anyone else in the area that requested it.

Back in the harbor, we had heard that there have been a lot of issues regarding propane tanks being stolen from the cages that were around the outside of the buildings; along with an ATM machine (you would be surprised how often that actually happens). It was assumed that it was being perpetrated by a local couple that lived nearby and we decided to take action immediately. These thefts were obviously not happening during the mornings or mid-day due to the high amount of business activity during these times; this job would require high-quality video being shot and recorded in the dark of night.

WTI’s Ambervision II had worked so well in previous jobs that it was yet again the prime choice for this new scenario. Taking the proper rout, we created our head end in a small room in one of the businesses only accessible by two people on a regular basis. We installed three Ambervision II cameras along the main wings of the building, followed by one more secured in a corner of a hallway to watch over the area where the ATM machine was located. To finish off the building, we mounted a C-MAX Ultra Dome on the roof.

The Channel Islands Harbor has had great success over the years and has progressed continuously day by day. This, of course, leads to expanding buildings and allowing more businesses to come in and create a home for themselves. While the new buildings were going up, we received a call to add more surveillance cameras; these were primarily for daytime use and an overall visual of the construction sites while the building was going on.

Taking the layout of the existing buildings, the one opposite of building A (the Ambervision II side) was where we decided to work from. A C-MAX camera was used in 4 different locations for this new job; one camera in the front, one in the back, and two facing out over the water. All of the cables for the new cameras were run back to the original room to allow all 8 cameras to be centrally monitored.

The business owner was able to watch day by day as the new building went up and save the video as needed. This set-up has not only worked as proper security for the area, but has also allowed the businesses to cut and save clips of video that they wanted for sentimental value of their expanding businesses.

Since the first day WTI’s cameras went up at the harbor, six years ago now, there has not been one theft or act of vandalism.

It has been extremely gratifying to watch this project evolve over the years; not only have we satisfied customer needs again and again, we have also helped make a local harbor safe for business and the community.

~Patrick Kearns, Product Specialist

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WTI (Wireless Technology, Inc.)

Video Surveillance Products Dedicated to the Broadcast, Global Security and Transportation Markets!

www.gotowti.com ● www.wirelesstech.com

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Keep an eye on your assets – anywhere, anytime!

Ah, the cellular telephone.

Seems like everyone has at least one of these cool little devices now-a-days. With a cell phone not only can you make and receive calls, you are able to take digital photos, record short videos, play games, text message, email, the list goes on and on. However, there was an important function missing… until now! Video surveillance has gone totally mobile!

With the affordability of surveillance systems, more and more are popping up everywhere; large businesses, small businesses, homes and various high-risk public places. People want to keep an eye on their assets, especially in difficult economic times like these. Company owners want to make sure employees and customers are not stealing from them, parents want to make sure that their homes and families are safe when they aren’t there; and until recently people with these systems needed a computer or to be at their video storage device to view the video.

Now, on the go, anywhere in the world a cellular telephone can be used to view the video – live or playback. In some instance all that is required is a specific application downloaded to your cell phone, in others (with certain DVRs) you can view the live feed on a web browser on the phone.

It’s amazing how quickly the cellular telephone evolved from a huge block phone that required a suitcase of components to operate into something that allows us to do everything we need to do in our daily lives in one compact hand-held device.

WTI offers every piece of the cell-phone viewable surveillance puzzle, except for the cell phone of course. With WTI cameras and DVR equipment, setting up a system that can be viewed anywhere in the world is as easy as 1-2-3! Check out the full line of solutions available at: http://www.gotowti.com/Products_Main.htm.

~The WTI Team

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WTI (Wireless Technology, Inc.)

Video Surveillance Products Dedicated to the Broadcast, Global Security and Transportation Markets!

www.gotowti.com ● www.wirelesstech.com

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