![Osborne-cw-01](https://upload.wikimedia.org/wikipedia/commons/b/ba/Osborne-cw-01.jpg)
The Osborne Fire Finder is a type of
alidade
An alidade () (archaic forms include alhidade, alhidad, alidad) or a turning board is a device that allows one to sight a distant object and use the line of sight to perform a task. This task can be, for example, to triangulate a scale map on site ...
used by
fire lookout
A fire lookout (partly also called a fire watcher) is a person assigned the duty to look for fire from atop a building known as a fire lookout tower. These towers are used in remote areas, normally on mountain tops with high elevation and a ...
s to find a directional bearing (
azimuth
An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north.
Mathematicall ...
) to smoke in order to alert fire crews to a
wildland fire
A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identif ...
.
History and development
The forerunner to the device was invented around 1840 by Sir
Francis Ronalds
Sir Francis Ronalds FRS (21 February 17888 August 1873) was an English scientist and inventor, and arguably the first electrical engineer. He was knighted for creating the first working electric telegraph over a substantial distance. In 1816 ...
to help combat fire in London – he also named his innovation the “Fire Finder”. Ronalds' fire finder comprised a
theodolite
A theodolite () is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but it is also used extensively for building and i ...
atop a watchtower. Bearings and vertical angles from the horizon to surrounding features were recorded either on a surrounding cylinder in the form of a
panorama
A panorama (formed from Greek πᾶν "all" + ὅραμα "view") is any wide-angle view or representation of a physical space, whether in painting, drawing, photography, film, seismic images, or 3D modeling. The word was originally coined in ...
or on a circular table at the base of the instrument. The location of any fire could thus be pinpointed even in the dark.
The modern version was created by William "W.B." Osborne, a
United States Forest Service
The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency inc ...
employee from
Portland, Oregon
Portland (, ) is a port city in the Pacific Northwest and the largest city in the U.S. state of Oregon. Situated at the confluence of the Willamette and Columbia rivers, Portland is the county seat of Multnomah County, the most populous co ...
, and has been in service since 1915. Mr. Osborne also designed the photo-recording transit for making panoramic records of forest conditions, as well as a collapsible water-bag knapsack for firefighting (U.S. patented in 1935). Many fire finders were manufactured from 1920 through 1935, but the manufacturer,
Leupold & Stevens, Inc., stopped production of replacement parts after 1975.
In recent years, with the resurgence and recovery of fire lookout towers, new Osborne devices were needed. The U.S. Forest Service, San Dimas Technology and Development Center (SDTDC) was contacted regarding the deteriorating condition of the Osborne Fire Finders housed in fire lookouts throughout the United States. A pilot program to create new Osbornes was coordinated with manufacturer Palmquist Tooling, Inc., and now Osborne Fire Finders are once again available.
Use
The system is composed of a
topographic map
In modern mapping, a topographic map or topographic sheet is a type of map characterized by large- scale detail and quantitative representation of relief features, usually using contour lines (connecting points of equal elevation), but historic ...
of the area oriented and centered on a horizontal table with a circular rim graduated in degrees (and fractions). Two sighting apertures are mounted above the map on opposite sides of the ring and slide around the arc.
![LookoutCharley01](https://upload.wikimedia.org/wikipedia/commons/4/4d/LookoutCharley01.JPG)
The device is used by moving the sights until the observer can peek through the nearer sighting hole and view the cross hairs in the further sight aligned with the fire. The fire lookout notes the degrees on the graduated ring beneath the sight. Early Fire Finders were capable of a crude estimate of elevation based upon the level and elevation of the table, calculating distance and rough position of the fire by reference to any distinctive terrain features and by use of the scale shown on the map. However, in actual practice, fire distance and location were normally established using two or more Fire Finder-equipped towers, using the ''
intersection
In mathematics, the intersection of two or more objects is another object consisting of everything that is contained in all of the objects simultaneously. For example, in Euclidean geometry, when two lines in a plane are not parallel, their i ...
'' method to fix the precise location of the fire. Dispatchers at a central facility used a
compass rose
A compass rose, sometimes called a wind rose, rose of the winds or compass star, is a figure on a compass, map, nautical chart, or monument used to display the orientation of the cardinal directions (north, east, south, and west) and their int ...
to mark lines of position from each reporting tower onto a large map to quickly find where the reported bearings intersect.
Today, a more precise determination of a fire location can be made by the use of a single Fire Finder in conjunction with a digital elevation model (DEM).
[Guth, pp. 1-10]
See also
*
Fire lookout tower
A fire lookout tower, fire tower or lookout tower, provides housing and protection for a person known as a "fire lookout" whose duty it is to search for wildfires in the wilderness. It is a small building, usually on the summit of a mountain or ...
*
Fire lookout
A fire lookout (partly also called a fire watcher) is a person assigned the duty to look for fire from atop a building known as a fire lookout tower. These towers are used in remote areas, normally on mountain tops with high elevation and a ...
*
Alidade
An alidade () (archaic forms include alhidade, alhidad, alidad) or a turning board is a device that allows one to sight a distant object and use the line of sight to perform a task. This task can be, for example, to triangulate a scale map on site ...
*
Plane table
A plane table (plain table prior to 1830) is a device used in surveying site mapping, exploration mapping, coastal navigation mapping, and related disciplines to provide a solid and level surface on which to make field drawings, charts and maps. ...
Notes
References
William B. Osborne profile USFS History section,
Forest History Society
The Forest History Society is an American non-profit organization dedicated to the preservation of forest and conservation history."Forest History Society." Echo Project. Center for History and New Media, George Mason University. http://echo.gmu. ...
website
* Mooers Jr., Robert L., ''Finding Your Way In The Outdoors'', Outdoor Life Press (1972),
Fire Management Tech TipsUSDA Forest Service, October 2003 Document: 0351 1311=SDTDC
External links
{{Commons category
History of the Osborne Fire Finder by Ray Kresek
Wildfire suppression equipment
Surveying instruments
1915 introductions