Jong Gyu Han, Keun Ho Ryu, Kwang Hoon Chi and Yeon Kwang Yeon Statistics Based Predictive Geo-Spatial Data Mining: Forest Fire Hazardous Area Mapping Application Jong Gyu Han, Keun Ho Ryu, Kwang Hoon Chi and Yeon Kwang Yeon 26-10-2003

Problem Definition -Forrest Fire Prevention Finding spatial-temporal distribution of forest fires Predicting forest fire hazardous areas from large spatial data sets Leads to a forest fire hazard prediction model 26-10-2003

Problem Definition 2 Youngdong Region of Kangwan Province, Republic of Korea Using: -Historical data on fire ignition point locations -Grid-based multi-layer GIS 26-10-2003

Prediction Methods Depends on relationship of spatial data sets relevant to forest fire with respect to areas of previous forest fire ignition N[S] = all area N[F] = fire ignition areas N[A] = forest type A N[E] = area of fire ignition on forest type A 26-10-2003

Conditional Probability Prediction Model Average density of ignition areas: P(F) = N[F]/N[S] Without other information this is the probability of a forest fire ignition area Favourability of finding a forest ignition area given the presence of forest type A: CondP(F\A) = P(A\F) · P(F) P(A) P(A\F) = P(A ∩ F) P(F) P(A ∩ F) = N[A ∩ F] / N[S] = N[E] / N[S] 26-10-2003

Conditional Probability Prediction Model Example N[S] = 100.000 N[F] = 500 N[A] = 2500 N[E] = 100 P(F) = N[F]/N[S] -> 500/100.000 = 0,005 P(A\F) = N[E]/N[S] -> 100/500 = 0.2 P (A) = N[A]/N[S] -> 2500/100.000 = 0.025 CondP(F\A) = ((N[F]/N[S]) · (N[E]/N[S])) / (N[A]/N[S]) -> 0,005 × 0.2/0.025 = 0.04 Given the presence of forest type A, the probability of a forest fire occurrence is 8 times greater than the prior probability 26-10-2003

Likelihood Ratio Prediction Model Represents the ratio of two spatial distribution functions: one with forest fire and one without occurrences LR(A\F) = P(A\F) P (A\F) LR(A\F) = N[E] · (N[S] – N[F]) N[F] · (N[A] – N[E]) N[E] · (N[S] – N[F]) = 100 * (100.000 - 500) = 9.950.000 N[F] · (N[A] – N[E]) = 500 * (2500 - 100) = 1.200.000 LR(A\F) = 9.950.000/1.200.000 = 8,2916 >1: positive evidence for forest ignition 1: uncorrelated <1: negatively correlated 26-10-2003

Prediction Procedure Forestry Maps Topography Maps Human Activities -Fire History Data -A large number of thematic layers can be suitable related to forest fire occurrences -Relevance filter is subjective -> Thematic layers are user-selected 26-10-2003

Forest Fire Hazard Rate Multiple Layer integration shares intermediate analysis with other levels FHR: Forest Fire Hazard Rate: FHR(p)CondP = CondP(V1(p)) ×…× CondP(Vm(p)), i=1,…,m FHR(p)LR = LR(V1(p)) ×…× LR(Vm(p)), i=1,…,m Vi(p) = Attribute value at the point thematic map (i) CondP = Conditional Probability LR = Likelihood Ratio For each local area, a FHR can be computed, and fire ignition danger can be analysed 26-10-2003

Experiment: Attribute selection For practical use, thematic layers must be selected, based on relative importance for explaining fire ignition Condition: chosen layers have to be conditionally independent Layers for Experiment: -Forest Type -Elevation Slope Road Network Farms Building Boundaries 26-10-2003

Experiment: Data sets -It is assumed the time of study was 1996: All spatial data in 1996 are compiled, including distribution of fire ignition locations which occurred prior to that year -Cross Validation: Predictions based on those relationships are evaluated by comparing the estimated hazard classes with the distribution of forest fire ignition locations that occurred after 1996, during the period 1997 to 2001 - Evaluation of Conditional Probability and Likelihood Ratio can expressed in a Prediction Rate Curve 26-10-2003

Expiriment: Evaluation Prediction rate curve of both models Conclusion: Likelihood Ratio is a more powerful method than Conditional Probability. The effectiveness of the model estimated are acceptable Prediction Rates with respect to the ‘future’ 1997 to 2001 forest fire occurrences 26-10-2003

Expiriment: Visualisation Using Forest Fire Hazard Index (FHI) -Sort estimated probabilities of all pixels in descending order -ordered pixels are divided into 11 classes: Pixels with the highest 5% estimated probability are classified as the first class, the next 5% as second class and so on. Remaining low 50% is assigned to the last class Add color to classes 26-10-2003

Conclusion Statistics based Forest Fire prediction works well. The Likelihood ratio method is more powerful than the Conditional probability method. Prediction of the forest fire hazardous area could be helpful to increase the efficiency of forest fire management: The ability to quantify the ignition risk could lead to a more informed allocation of fire prevention resources. 26-10-2003

Questions 26-10-2003