Surveillance Pole Selection GuideAuthor: Brian Rhodes, Published on Jul 25, 2012
Successfully selecting poles for mounting cameras is tricky business. Despite what seems to be straightforward process, selecting the right type of pole for placing a camera is made difficult by the vast choices to pick from. In this note, we cover the major shapes and material types involved when selecting poles of video surveillance applications.
The following information is a general guide, but the exact application is subject to specific design and code approvals. Especially when it comes to material selection, a variety of engineering opinions exist over which is more suitable for use at a given mounting height. In all cases, the matter of exact pole specification is a design consultation between local authorities, pole designer/manufacturers, and the installer. The first step in this process is to gather all three parties together on the issue before proceeding.
Pole design has a tremendous effect of video quality, especially when considering image stability. Aside from balance loading and wind deflection, the pole foundation, soil compactness, and cantilevered camera mounting arms compound the natural tendency to move. The three major methods of dealing with deflection or sway are:
- Choosing the Appropriate pole type: The best way to ensure camera stability is picking the appropriate pole type based on design constraints like camera type, mounting height required, and equipment weight.
- Structural Stiffeners: Engineered embellishments can be made to the pole itself, including guy wire kits, stiffening gussets, or reinforcement plates. However, these modifications are often custom designed and fabricated and are costly to implement.
- Electronic Image Stabilizers: Some cameras or auxiliary 3rd party appliances have the electronic means to stabilize video images and reduce the amount of 'shake' present.
Especially with PTZs and other 'motion sensitive' video deployments, like video analytics, ambient sway and deflected movement of cameras can be a huge problem. When a PTZ is at 'full zoom', even the most subtle movement translates into feet of sway in the zoomed FoV. Given the variables involved, prior design consideration is the easiest answer to mitigate these problems.
What Type of Pole to Use?
This process does not need to be exceedingly complex. Sometimes the 'right' answer is simply taking examples of nearby poles, installed by local subcontractors, and making a few specification changes to the installed examples to suit video applications. In general, utility poles can be readily adapted to host security cameras. However, when confronted with a true 'greenfield' scenario,there are some questions to ask before moving forward:
- What is the optimal mount height of the camera on the pole?
- How many cameras in total are to be mounted on the pole?
- Will these cameras directly mount to the pole, or are additional mounting brackets necessary?
- What is the total estimated weight of all pole mounted equipment, including power and cabling? This often is manually calculated by gathering weight information from manufacturer data sheets.
Rules of thumb when considering poles:
- When mounting a camera under 15' above the ground, where cost is the primary constraint, square steel poles are a good choice.
- When looking to mount cameras between 15' and 60' round or tapered steel, aluminum, or timber poles are the best choice.
- When looking to mount cameras above 20' and rigidity is the primary driver, prestressed concrete or steel tapered or octagonal poles are typically the best options.
Square: These poles are often simple to manufacture and cheap, but this shape is most prone to movement, twisting, and wind load. Unless mounting a camera under 15' or less, square poles are poor choices to mount cameras. Typically this profile is found in metallic and prestressed concrete poles.
Round: Timber poles, and inexpensive metallic poles are most often round sections. This profile is more resistant to wind loads than square profiles, but they are often heavier and require more substantial footings. Because round sections are prone to sway in high winds and twist with torsional loads, they are suitable for mounting cameras under 50' but may require external stiffening at greater heights. All types of pole materials are available in this profile.
Tapered: This is the most common pole profile in use for surveillance applications. These are 'modified round' profiles that are wider at the base at at full height. While the advanced shaping is more costly to manufacture than pure 'round' poles, the profile permits greater overall heights, loads, and are more rigid at height than round poles. All types of pole materials are available in this profile.
Octagonal: The newest engineered profile is the 'octagonal', or 'eight sided' profile. This designed profile is stronger and more rigid than other shapes, and is an extremely stable platform for mounting surveillance cameras. Many times, electrical utility poles and stadium lighting poles use this profile. The shape is not easy to form with natural materials, so the profile is most often found in metallic and prestressed concrete poles. However, due to the exacting machining processes used, octagonal forms are the most costly.
Steel and Aluminum
Strengths: Metallic poles are the mainstay material used in surveillance camera systems, primarily because the are engineered to exact specifications not subject to the natural variations of timber. Metallic poles can be furnished in modular pieces, with total heights exceeding 110' feet, but in transportable segments. In applications were soil quality or footing designs are limited, lightweight aluminum poles can be used in place of steel. Galvanized or anodized finishes result in service life measured in hundreds of years. If properly maintained, these poles can be indefinitely used.
Price: In the height range most surveillance cameras are mounted - between 20' to 45' feet, steel poles are near equal to timber poles. Beyond those heights, steel is roughly 10% less expensive than aluminum, but significantly less expensive than timber, due to simplified manufacturing techniques and plentiful base alloys. A single 26', 7 gauge hot-rolled steel pole can be purchased for about $950, or about $36.50 per foot.
Limitations: Because of the extreme heights and installation complexity (welding, bolting, etc), specialty pole erectors are often required to be used during installation. Exacting installation specifications on bolt torque tightness and welding quality often prevent these poles from general purpose surveillance use.
Strengths: Certain varieties of Pine and Fir make good poles because of their natural freestanding height and resistance to rot. Often, these poles are preserved, or incised, with creosote or other chemicals to extend service life up to 80 years. Timber poles are commonly sized in 25' to 45' lengths, although lengths up to 110' are available.
Price: Timber pole pricing is heavily negotiated, and total purchase quantities significantly influence resell price. However, a single 26' yellow pine pole can be purchased for about $1000, or about $38.50 per foot.
Limitations: Frequently these poles must be freighted in one piece, and unlike metallic or concrete alternatives, they cannot be reassembled on site. This shipping restriction may limit pole heights to transportation requirements. Regions with high humidity and termite problems can experience service life of only a few years beyond what simple upkeep provides.
Strengths: Prestressed concrete poles provide the most rigid, stable material to mount cameras upon. Once set into place, this type of pole requires little maintenance. Prestressed concrete poles are available in freestanding units up to 70 foot heights.
Price: A single 26' concrete pole can be purchased for about $2350, or about $90.00 per foot.
Limitations: The manufacturers of these poles are much less common than steel or timber, and finding a local or regional source can be difficult. The resulting cost of freight is higher, further pushing the price higher compared to cheaper alternatives. While prestressed concrete has many material advantages, the type has not gained widespread familiarity among installers, inspectors, or end users, and approvals may be harder to achieve than with 'traditional' materials.
Strengths: Cast iron lends itself to ornamental applications. Typically, cast irons poles are used to make surveillance less obtrusive by blending to existing light fixtures or architectural elements. Less obtrusive poles may result in less vandalism and more effective surveillance.
Price: Cast Iron poles are commonly sized in 15' to 35' lengths. Final pricing is highly dependent on cosmetic features and However, a single 26' ornamental pole can be purchased for about $2000, or about $77.00 per foot.
Limitations: Case Irons poles are generally bought on the basis of cosmetics, not load rating. As such, this material may not hold more than a single camera. Performance aspects like stability and wind deflection are subject to specific cosmetic profiles, and the material needs to be frequently painted to prevent corrosion. They often are sold in assemblies that must be installed in sections and take more installation time than the simpler profiles mentioned above.
Once selection has been made, only a portion of the work is complete. See our "Primer on Pole Mounting Cameras" for further details on installing cameras onto poles and installing poles themselves.
Local codes have final authority over pole selection. Pole characteristics like material type and height are frequently governed by local authorities and local jurisdictions. Commercially, poles for video surveillance can be purchased in COTS heights between 10 and 60 foot heights. However, despite the range of heights and options, local code inspectors should be consulted before final specifications are written.
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