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Standard Forest Service Designs for Rappel Towers

Dave Gasvoda, Project Leader

This report describes commercially available handheld infrared (IR) viewers (Figure 1) and presents information to help Forest Service employees make purchasing decisions. A low-cost infrared temperature scanner and thermometer were evaluated and found unsatisfactory for wildland fire applications.

Figure 1—The Palm handheld infrared viewer.

The two largest manufacturers of IR viewers are FLIR Systems and Raytheon Systems. Several smaller companies offer suitable viewers. New, less expensive equipment is likely to be introduced in the coming year.

Table 1 lists IR viewers that are suitable for aerial and ground wildland fire applications.

Infrared Viewers

The spectrum column of Table 1 shows the wave-length of infrared energy that the detector is sensitive to. Current viewers operate in the 3- to 5-micron portion of the middle infrared or the 7- to 14-micron portion of the far infrared spectrum. In theory, viewers operating in the far infrared are less likely to see hot gases and solar reflections. Also, they can see through smoke better. However, for fire applications the differences in demonstrated performance between equipment operating in the middle and far infrared ranges of the spectrum are not significant.

Several detector technologies are currently being used. The technologies can be divided into two major classes, cooled and uncooled. Uncooled detectors allow for the lightest-weight, most-compact, lowest-power-consumption, and least-expensive equipment. Thermoelectric cooling is a reliable means of cooling detectors that must be operated at low temperatures. It is also used to stabilize the temperature of some uncooled detectors. Sterling coolers have been developed that are compact and can operate reliably for 5,000 hours.

The array size, or resolution, determines how small an object can be resolved and how clearly larger objects can defined. Large arrays are desirable.

Lightweight, compact units reduce operator fatigue.

Battery life, power consumption, size, and weight are closely related. A low-power design requires less battery power for a given period and reduces overall weight and size.

The price column gives the list prices and discounted prices, where applicable. The Government Services Administration price is given for items covered by the schedule. Raytheon sells through distributors who sometimes offer special prices lower than the list price. Considerable savings can be obtained by getting competitive price quotes. Demonstrator units are usually substantially discounted. This report includes a list of Raytheon dealers. Contact information is provided for other manufacturers. Sierra Pacific Innovations sells thermal viewers from several manufacturers and offers demo prices.

Any of the listed thermal viewers are likely to provide satisfactory results. However, ergonomics is an important consideration. Equipment should be evaluated under field conditions before it is purchased.

Black-and-white viewfinders are good for handheld ground applications. A remote display is advisable when IR viewers are in aircraft. Remote displays reduce fatigue and motion sickness. Many IR viewers that have eyepiece viewfinders also have a standard video output that can be connected to one or more battery-powered color LCD monitors. High-contrast monitors that can be viewed in bright light are available from sources such as Marshall Electronics, Inc., for $225 or more, depending on size and features.

Lens length determines the field of view and the apparent size of a viewed object. The lens specifications for infrared viewers are similar to those used in standard cameras. The viewers' standard lens length of 50 mm to 75 mm is suitable for the majority of applications. Longer lenses provide increased magnification, but decrease the field of view. Image blur increases with longer lenses because users cannot hold the viewer steady. Long lenses are more expensive and heavier than standard lenses. Lenses that are shorter than the standard lenses increase the field of view but decrease the apparent size of objects. Some small objects may not be visible at all.

The standard lens provides a reasonable tradeoff, allowing a fairly large area to be seen with a reasonable amount of detail. Standard lens lengths have proven to be suitable for aerial observations at altitudes of 500 to 2,000 feet above ground. The expensive NightMaster from Cincinnati Electronics Corp. allows the user to select a 50- or 250-mm lens by twisting a ring. Electronic zoom lenses increase the size of the viewed object, but do so at the expense of resolution. They basically just reduce the number of pixels displayed while increasing the size of each pixel.

Infrared viewers should have manual adjustments for gain and contrast. These adjustments will allow an experienced operator to adjust the display so that hot targets stand out from the background with a minimal loss of detail.

Infrared Temperature Scanner and Thermometer

Infrared temperature scanners and thermometers are used to measure temperature when conventional sensors cannot be used. These applications include measuring the temperature of moving or hazardous objects (for instance, when high voltage is present), or to protect the objects being measured from con-tamination. The scanner and thermometer operate on principles similar to those used in the infrared viewers. They might be thought of as single-pixel viewers with a temperature display. The field of view is an impor-tant consideration.

The optics of the unit determines the field of view, which increases as the distance to the observed object increases. The pyrometer determines the average temperature of all surfaces within the field of view. For an accurate temperature measurement, the object must fill the entire field of view.

The two instruments evaluated had different fields of view. The Omega OS93 infrared scanner has a narrow field of view where the spot diameter is: 0.625 + (distance to object/87) inches. The Omega OS520 has a medium field of view where the spot diameter is: distance to the object/10.

Fire hotspots would not need to fill the entire field of view, but the hotspot would need to have a tempera-ture noticeably higher than the background for it to be detected. Table 2 shows the theoretical temperature reading produced by hot objects that do not fill the entire field of view. The hotspot's temperature was assumed to be 932 °F (500 °C) and the background temperature was assumed to be 77 °F (25 °C).

The OS93, with its narrow field of view, can detect a 1-inch (2.5-cm)-diameter hotspot over 10 feet (3 meters) away. It can detect a 6-inch (15-cm)-diameter hotspot over 100 feet (30 meters) away. The small field of view, 2 inches at 10 feet (3 meters) or 14 inches (36 cm) at 100 feet (30 meters), requires that the instrument be carefully aimed and moved to com-pletely cover an area. It would not be practical to survey a large area with the OS93 because it would take too long and the operator would become fatigued.

The OS520 has a larger spot size that makes it easier to scan an area. The spot size is 6 inches (15 cm) at 5 feet (1.5 meters) or 12 inches (30 cm) at 10 feet (3 meters). However, the OS520's ability to detect a hotspot is considerably reduced. The maximum range to detect an 1-inch (2.5-cm) spot is 5 feet (1.5 meters). The maximum range to detect a 6-inch (15-cm) object is 10 feet (3 meters).

The OS520 thermometer has an audible and visible alarm that can be set to go off when the temperature is higher than an alarm point. When the alarm is set a few degrees above the warmest background temperature, the alarm will go off when the unit scans a hotspot. The operator does not have to concentrate on the displayed temperature reading. Table 3 shows specifications of the OS93 and OS520 thermometers.

Field Evaluation

The infrared scanner and thermometer were given to two interagency hotshot crew members for evaluation in hotspot mopup operations. The crew members liked the concept of using relatively inexpensive instruments to detect hotspots that might otherwise be overlooked. However, the infrared pyrometer performance was inconsistent. Its maximum usable range was about 5 feet (1.5 meters).

The units would respond when aimed at known hotspots, but they missed many hotspots when they were used to scan an area. This probably occurred because the unit must be pointed directly at a hotspot. It is difficult to completely scan a large area without having gaps in the coverage. The unit could be used to supplement conventional cold-trailing techniques by using it to look at hard-to-reach areas. Conventional techniques are more reliable and cost effective. These infrared units cannot reliably be used to detect hotspots.

Conclusions

Handheld infrared viewers are useful tools for locating hotspots during mopup and can see through smoke to help locate the borders of a fire. They can be used in aerial and ground operations.

Improvements in recent years have made the units smaller, lighter, more reliable, and easier to use. Prices have fallen substantially and are likely to fall farther in the next few years.

The handheld infrared thermometer and scanner devices commonly used in industry do not have any suitable applications for wildland fire activities because their detection range is short and their field of view is narrow.

Company List

Cincinnati Electronics Corp.
7500 Innovation Way
Mason, OH 45040-9699
Phone: 513-573-6744
Fax: 513-573-6290
E-mail: greed@cinele.com
Web site: http://www.cinele.com/

FLIR Systems, Inc. Western USA)
16505 SW 72nd Avenue
Portland, OR 97224
Telephone: 503-684-3731
Fax: 503-684-3207
E-mail: marketing@flir.com
Web site: http://www.flir.com

FLIR Systems, Inc. (National)
16 Esquire Road
North Billerica, MA 01862
Phone: 978-901-8363 or 800-GOINFRA
Matt McGini

Infrared Components Corp.
2306 Bleecker Street
Utica, NY 13501
Phone: 315-732-5020
Fax: 315-732-5931
E-mail: marketing@infraredcomponents.com
Web site: http://www.infraredcomponents.com/

Fluke Corporation
PO Box 9090
Everett, WA USA 98206
Phone: (425) 347-6100
Fax: (425) 446-5116
Toll Free: 1-800-44-FLUKE (1-800-443-5853)
Web site: http://us.fluke.com/usen/home/default.htm

Marshall Electronics, Inc.
P.O. Box 2027
Culver City, CA 90231
Phone: 310-390-6608 or 800-800-6608
Fax: 310-391-8926
Web site: http://www.mars-cam.com

Monroe Infrared Technology, Inc.
P.O. Box 1058
Kennebunk, ME 04043
Phone: 800-221-0163
Fax: 207-985-3146
E-mail: miti@gwi.net
Web site: http://www.monroeinfrared.com/

Sierra Pacific Innovations
1034 Emerald Bay Rd., Dept. 437
South Lake Tahoe, CA 96150
Phone: 530-543-1186
24-hour live: 805-320-4024
Fax: 530-543-1153
E-mail: sales@x20.org
Government Agencies/Law Enforcement/Resellers: steve@x20.org
Web site: http://www.x20.org/thermal/index.htm

Raytheon Distributors

Accurate Locators
521 S. Central Avenue
Medford, OR 9750
Phone: 541-855-1590
Fax: 541-855-1023
Wayne Good

Bcon, Inc.
8333 Seaview Street
Anchorage, AK 99502
Phone: 907-243-2634
Fax: 907-243-7220
Bryan Bazemore

Canyon State Emergency Products
8557 N. 78th Avenue
Peoria, AZ 85345
Phone: 602-979-0434
Fax: 602-979-6949
Tom Webber

Compix
P.O. Box 885
Tualatin, OR 97062-0885
Phone: 503-639-8496
Fax: 503-639-1934
Jirn Walcutt

G & A Electronics
120-C Tustin Avenue
Newport Beach, CA 92663
Phone: 949-645-5431
Fax: 949-645-5435
Mark Upson

Infrared, Inc.
P.O. Box 20369
Reno, NV 89515
Phone: 775-827-2440
Fax: 775-827-2441
Jerry Gamroth

Lehr Auto Electric
3001 L Street
Sacramento, CA 95816
Phone: 916-739-6626
Fax: 916-739-1496
Ken Lehr

B.E. Meyers & Co., Inc.
17525 N.E. 67th Ct.
Redmond, WA 98052
Phone: 425-881-6648
Fax: 425-867-1759
Roger Kreitzberg

P & R Technology
P.O. Box 606
Portland, OR 97207
Phone: 503-292-8682
Fax: 503-292-8697
George Osgood

Pipkorn's of Oshkosh
1255 Merritt Avenue
Oshkosh, WI 54901
Phone: 920-236-6423
Fax: 920-236-8784
Skip Pipkorn

Puget Sound Instrument Co.
4611 11th Avenue, N.W.
Seattle, WA 98107
Phone: 206-789-1198
Fax: 206-789-7391
Tracy Prescott

Pursuit
880 Howe Road, No. A
Martinez, CA 94553
Phone: 925-370-2144
Fax: 925-370-2087
Al Boyce

Remote Satellite Systems International
1010 Lootens Place No.17
San Rafael, CA 94901
Phone: 415-256-8199
Fax: 415-256-819
Robert Rosen

Skaggs Telecommunications Service
5290 S. Main Street
Murray, UT 84107
Phone: 801-261-4400
Fax: 801-261-1580
Robert Swenson

Streichers
4777 N. 124th Street
Butler, WI 53007-0605
Phone: 414-781-2552
Fax: 414-781-0444
Ed Marben

Western Sensor
P.O. Box 1658
Hayden, ID 83835
Phone: 208-772-3291
Fax: 208-772-4471
Glen G. Hogan

About the Author

Dave Gasvoda has a bachelor's degree in electrical engineering from Montana State University. He joined the Missoula Technology and Development Center in 1969 and has worked on a wide variety of projects since then. Electronic devices he designed have saved Forest Service employees backbreaking labor. He has been awarded two patents.

Additional single copies of this document may be ordered from:
USDA Forest Service
Missoula Technology and Development Center
Building 1, Fort Missoula
Missoula, MT 59804-7294
Phone: 406-329-3978
Fax: 406-329-3719
E-mail: pubs/wo_mtdc@fs.fed.us

For additional technical information, contact Dave Gasvoda at the address at top.
Phone: 406-329-3986
Fax: 406-329-3719
E-mail: dgasvoda@fs.fed.us
Lotus Notes: David S Gasvoda/WO/USDAFS

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USDA Forest Service, Technology and Development Last Modified: 03/30/2013 03:04:37