Author: Delio Tortosa and Paul McBay
Company: ELIRIS Inc.
The team implemented the use of portable GPS/desktop-GIS in a jointly sponsored project by Forestry Canada the Ontario Ministry of Natural Resources. The objective was to use ground and helicopter-borne GPS to provide a rapid, cost-effective way of mapping fire perimeters, identify and locate hot spots, provide decision support, and a quicker response time for a District Fire Office.
Manual techniques are presently used to locate and map forest fires on paper maps and to perform spatial analysis on fire data to support management planning and decision-making in the field.
In 1991, trials were conducted by the Ontario Ministry of Natural Resources in the Timmins District to demonstrate the use of airborne GPS and GIS (Arc/Info) for the 1991 GOGAMA 4 Wildfire. These tests indicated that helicopter borne GPS provides a rapid and accurate acquisition of the fire perimeter. Although supplementary aerial photography provided more accuracy, the time and expense required to analyze the photography limited its usefulness to final fire mapping. The GPS trials demonstrated the potential to acquire perimeters with sufficient accuracy for remapping fires through their growing stage as often as required to support fire suppression planning.
The time, effort and number of staff required to produce maps manually in the fire camp also limited the number of mapping updates that could be done. The GIS technology used for the Timmins pilot project was not easily transported into the field, required GIS specialists and support staff and has a high cost. There is a need for a less sophisticated, portable mapping software in the hands of fire staff that can be used to support fire operations.
The objective of the project reported in this paper was to demonstrate the feasibility of implementing a user-friendly, portable, low-cost technology using a Global Positioning System (GPS) receiver and a notebook-based desktop mapping system for support of fire management operations both in the field and at Fire Operations Headquarters.
The project was funded by the Canada/Ontario Northern Ontario Development Agreement, Northern Forestry Program (Project #4201).
Methodology: The project consisted of three phases:The initial task was to identify the activities carried-out by the District Fire Operations Headquarters (Ontario Ministry of Natural Resources) and the Fire Research Section (Forestry Canada) in order to determine the types of data to be defined as part of the GPS/desktop mapping system.
General requirements included:A 1:50,000 map-size area was selected around the Ranger Lake Fire Attack Base north of Sault Ste. Marie as a test block within which the available fire values information would be entered and serve to provide fire intelligence information.
GPS Receivers: Two GPS receivers were used during the project: a Magellan NAV 5000 PRO, 5-channel GPS receiver and a Garmin SRVY II, 8-channel GPS receiver. The Magellan NAV 5000 PRO was used during the initial field trials and the Garmin SRVY II was used during the operational phase.
Computer Hardware: The computer system consists of an notebook 386-SX25 with 387 co-processor and 80 Mb hard disk, a mouse, and a Super VGA monitor. This system has sufficient speed and hard disk capacity to meet the software and data requirements of the project. An HP Deskjet printer was used to generate color maps.
Computer Software: QUIKMap, a desktop mapping software was used together with ELINX, a GPS-desktop mapping shell which links to the Magellan and Garmin GPS receivers. For the training requirements, a Desktop Mapping/GIS Training Manual was provided consisting of exercises and accompanying digital data. An HPGL Emulation Software (DeskPlotter), accessible through the ELINX shell, allows the HP Deskjet printer to emulate a plotter and thereby produce high quality maps.
Basemaps: Four digital National Topographic Series (NTS) maps were translated to QUIKMap format: 41J, 41K, 41N and 41O. Each NTS area map was subdivided into four separate digital basemaps: Drainage, Topography, Transportation, and Miscellaneous Features. The change to QUIKMap format reduces the size of the digital maps such that complete NTS coverage of the test block requires about 10 megabytes of harddisk space.
Fire Values Database: The following seven separate database files were set up to capture and display the Ontario Ministry of Natural Resources Fire Values information for the Ranger Lake Test Block, a rectangular area 60 km by 45 km (2880 sq. km.):
Campgrnd - campgrounds, crown access pointsAdditional natural resource information such as nesting sites (raptors), Waste Disposal Sites, and Moose Aquatic Areas were obtained from the Sault Ste. Marie MNR District Office and entered into the Desktop Mapping System to supplement the Fire Values information. A sample of the Fire Values database file structure is shown on Table 1.
GPS data was transferred as point information containing position, time, and other satellite information, into a database file structure (Table 1). A similar database file structure was constructed for polygon/polyline information (Table 1). In addition to the GPS data fields, each record contains fields pertaining to the desktop mapping software (ie. symbol, line, color, etc.).
The portable GPS-desktop mapping system was set up in the Ranger Lake Fire Attack Base. A fire crew, consisting of three individuals, was designated for the project and training was provided on the Magellan NAV 5000 PRO and Garmin SRVY II receivers. The Crew Leader was provided with additional training on the use of ELINX (GPS-desktop mapping link), GPS Post- Processing Software, and QUIKMap (desktop mapping software).
Part of the training involved the transfer of natural resource data obtained from the Sault Ste. Marie MNR District Office into the QUIKMap desktop mapping environment. The Crew Leader was also trained in the basics of digitizing polygons in the desktop mapping system.
During the course of the field work, the GPS/desktop mapping system was transferred between the Ranger Lake Fire Attack Base and Sault Ste. Marie several times. Dismantling and packaging the entire system by two people was completed within one half hour.
For remote field operations, a separate tent on plywood flooring is recommended; a 120 volt power supply (ie. a gasoline-powered electric generator) is required to operate the printer and monitor, although the notebook computer can be used on internal batteries for about 1.5 hours before recharging is required.
Antenna Configuration: During the initial field trials using the Magellan NAV 5000 PRO, a critical step in configuring the system was the placement of the external GPS antenna on the helicopter. Improper placement of the antenna will result in large areas of satellite blockage by the helicopter fuselage. It should be emphasized that in order to do GPS mapping or tracking, there is a requirement for continuous GPS positions. This can be maximized by selecting an optimum location on the aircraft where the satellites will be visible continuously .
For the field trials the Magellan GPS antenna was bolted directly onto the roof of the cockpit on a 204B helicopter. This resulted in a very secure connection to the airframe with good signal reception. The GPS antenna cable was threaded through a small 1 centimeter diameter opening, into the cockpit and to the passenger area.
However, during operational testing of the GPS/desktop-mapping system using the Garmin SRVY II, the detachable antenna was mounted to the dash of the helicopter using a clamp in a location which provided maximum satellite visibility. The detachable GPS antenna also provided portability between different helicopters and rapid re-deployment for ground applications. An external aircraft antenna installation was not required.
Satellite Signal Reception: GPS signal reception was found to be satisfactory using the antenna configurations mentioned previously. Difficulties with GPS signal reception arose when the external GPS antenna was blocked by the helicopter fuselage as the pilot banked the aircraft (up to 30o), or when moving forward to gain speed which produced a forward tilt on the airframe of up to 30o.
The airframe of the helicopter interrupts the GPS satellite signal depending on the orientation and attitude of the helicopter and the position of a satellite at that particular moment. Loss of the GPS signal is generally temporary and can be re-acquired as the helicopter changes position. In addition, if the GPS receiver is capable of accessing 8-10 GPS satellite channels, the signal interruption has a negligible effect on the ability of acquiring a position fix (Garmin SRVY II).
Mapping Fire Perimeters: Aerial GPS surveys were completed for several small fires (Sault 28 and 14; < 100 Ha) and one large fire area (Sudbury 23, 1933 Ha). Sault Fire 28 (figure 1) and Fire 14 were flown using the Magellan GPS in 3D mode and at a sample update rate of 1 per second. The fire perimeters were mapped at a constant elevation which was 100 feet above the highest point of land covered by the fire. The helicopter was flown in light winds at 15 kph and no banking was required. The helicopter faced the wind direction at all times.
These trials provided good results, with the GPS receiver acquiring sufficient number of points to give a good resolution to the fire boundary (figure 1). Some data gaps occurred when a satellite was blocked by the engine/rotor assembly, depending on the direction the helicopter was facing.
Other trials were attempted in moderate winds conditions and following topography at 50-100 feet above tree tops. The result was higher helicopter speeds, excessive banking, satellite signal reception problems in the valleys, and a fair to poor definition of the fire boundary. It should be noted that for larger fires in less rugged terrain, these same conditions could provide a suitable definition for the fire perimeter. Such was the case for Sudbury 23 which was flown with the Garmin SRVY II at a sample rate of 1 position per second. Satellite coverage was good and the fire perimeter was flown in 31 minutes (figure 2), compared to 90 minutes using hand-sketching.
Hand-sketched outlines of the fire boundaries compare well with the GPS-derived fire boundaries (figure 3). The hand-sketched boundary is more generalized and displays less detail. In areas where there are few geographic controls (streams, lakes, etc.) the hand sketch is very generalized whereas the GPS-derived outline continues to display the same level of detail as elsewhere. The system allows for quick mapping and dissemination of map products, and a shorter turnaround for remapping.
Values Mapping: The traditional method for representing values information is to estimate the location of a value to protect (ie. hunting cabin) based on visual approximation or from any available map or file information. No geographic coordinate correlation exists between the paper files containing the attribute information and the paper maps.
Using aerial GPS, an absolute coordinate was obtained by hovering directly over the value until the GPS acquired a reading. Generally, an average of twenty-five readings provides a good estimate of the location. The location of resource values was also determined using ground GPS.
The fire values database contains both geographic coordinate and attribute information which can be easily manipulated on the digital base map or in the database. Using the GPS locations as a benchmark, it is possible to estimate the level of accuracy in the original fire values data. With continued use of GPS to georeference fire values, the overall quality of the database will be improved.
Hot Spot Location: Traditionally, hot spot fires are located by infra-red scanning from a helicopter, marked on a map or airphoto, and identified on the ground using white 'ticker tape' which is thrown out from the helicopter to mark the spot. The estimated location is then passed on to the ground crew who take a compass bearing and attempt to re-locate the hot spot. The accuracy of the hot spot location is dependent on the geographic features available and capability of the person mapping. If the helicopter is available, it may hover over the fire while the ground crew get a compass bearing on the location.
For this trial the helicopter hovered over the hot spot and recorded the location using a helicopter-borne GPS. An averaged GPS position fix of the location was then relayed to the ground crew. The GPS coordinate was then entered as a 'WAYPOINT' into the ground GPS receiver. This provided the ground crew with information on distance and bearing. With this information the Fire Crew Leader can estimate the length of hose required to reach the hot spot from the nearest body of water.
The results of three trials indicated that GPS in combination with the traditional compass method provides the most satisfactory results. It is not necessary to use the ground GPS receiver continuously in order to locate the hot spot; stopping and reading the GPS every few minutes provides information on distance and bearing to the waypoint (hot spot). This provides the fire crew with mid-course corrections which can be used to redirect the compass bearing. Using the GPS assisted method the time to locate the hot spots was limited to the traverse time; no searching was required. This can represent a time saving of up to 90%.
In thickly forested areas the NAV 5000 PRO GPS receiver had difficulty locking-in on the satellite signal while in a mobile, continuous mode. The GPS satellite signals are interrupted by the foliage when walking through thick bush. A GPS reading can be more easily acquired when stationary.
Accuracy and Precision using GPS: The full capabilities of the Global Positioning System are limited to 100 metres root mean square (rms) referred to as 'selective availability' (S/A) and imposed artificially on civilian users. The effects of selective availability may be removed through the use of differential GPS. Differential GPS was not used for the current study, since a +/- 50 metre precision provided sufficient detail at the scale of a forest fire. In addition, the 1:250,000 digital base maps have an inherent inaccuracy of up to a maximum of +/-100 metres. Accuracy limits for a 1:20,000 OBM are about +/-10 metres.
For the location of fire values such as dwellings, outpost camps, etc., an averaged GPS position provides sufficient precision for the level of detail required. Averaging GPS readings against a known benchmark provide a good measure of the accuracy and precision of a single GPS receiver.
Fire Impact on Forest Values: The impact of a forest fire on the forest stands can be quickly calculated by overlaying the fire boundary polygon (derived from the GPS mapping) over the forest stand polygons (derived from the Forest Resource Inventory, MNR) for the area (figure 4). Current limitations on the use of this method within the study area are the lack of digital OBM and digitized Forest Resource Inventory maps. An alternative would be to transfer reclassified LANDSAT imagery as polygons to the desktop-mapping system.
Rate of Fire Advance: Due to the low fire hazard during the field portion of the project, no tests could be made on active forest fires in the project area. In order to assess the capabilities of the portable GPS/desktop-mapping system in an active fire situation, the same system was used to map the progress of grass fires in South Africa (figure 5). Since the GPS receiver provides both geographic coordinates as well as the time, it is possible to calculate the rate of advance along the fire front and the rate of fuel consumption for a given area.
Decision Support: With a portable GPS/desktop mapping system, a Fire Attack Base has a system containing fire and natural resource values which can be quickly accessed, and a fast and accurate method by which to map the progress of a forest fire, locate hot spots and fire values, and be confident in the level of accuracy of the data. Simple spatial or database queries can quickly provide the fire supervisor with information on which to decide how fire fighting resources should be allocated and determine the values at risk and their level of priority.
Example A: Fire Attack Base Response Radius: In this example, the fire archive digital data from the years 1982-1992 for the Sault Ste. Marie District was transferred into the QUIKMap environment. This information was plotted on 1:250,000 EMR digital basemap in order to illustrate the pattern of fire occurrence and assist the fire manager in locating the most suitable location for a helicopter within the Sault Ste. Marie District. The procedure involved tagging and counting the number of fire starts within a 90 kilometer radius of Ranger Lake, Sault Ste. Marie, and Blind River. The result of this simple query indicated that Ranger Lake was the most appropriate location (figure 6).
Example B: Fire Intelligence and Operations Support: Members of several Provincial Fire Teams participated in the design of a database which would support their particular operations. Two datafiles were created: CREWINFO, a point file, containing information such as crew name, home base, last days off, regular working hours, etc., and HOSELINE, a polyline/polygon/point file, which contained fields such as number of lengths of hose, number of pumps, and other fire equipment.
Geographic coordinates can be derived with the GPS receiver along with basic attribute and descriptive information which can be entered while in the field. The GPS data can then be transferred and appended to the datafiles in order to update the Fire Intelligence and Operations Map (figure 7).
Data Transfer to Raster and Vector-Based GIS: Although the desktop mapping system has limited spatial analysis capabilities, these were sufficient to meet all the requirements of the field personnel at a fire attack base or District office. For further analysis, the data can be transferred easily to more advanced geographic information systems (ie. Arc/Info, SPANS, IDRISI) using available translators.
The results indicate that a portable GPS/Desktop-Mapping System can be integrated into the daily operations of a typical fire attack base and can be relocated quickly into temporary field camps to support fire management operations. Fire crew personnel can be trained in the use of GPS and desktop mapping within a week. Information on the area and the perimeter of a fire is available immediately after the transfer of the GPS data; high quality maps showing values at risk, the perimeter of the fire with drainage, topography and transportation routes can be produced within a few minutes on an inkjet printer in the field.
The results of the project will be used in the design of future phases of the Fire Management Information System currently being developed by the Ontario Ministry of Natural Resources.