Application of Change Detection Algorithms for Mine Environment Monitoring
Joseph Cacdac
9th Floor, Valero Tower
Valero St., makati City, Philippines
Tel : (63-2) 892-8026 Fax: (63-2) 817-9491
E-Mail: dames@portalinc.com
Abstract
Various changes detection algorithms are applied to multitemporal SPOT X S imagery of the Dizon large open pit mine area in San Marcelino, Zambales to investigate which techniques are suitable for mine environment monitoring. Techniques studies include image differencing, image-to-image ratioing, and principal components analysis. Change features are identified and detection by principal components analysis of a merged multitemporal data set is the most effective for mine environment monitoring.
Introduction
Remote sensing is proving to be suitable and cost-effective tool for certain components of environmental studies, especially those which are relevant in terms of content and scale, such as land cover and land use, water quality, landforms, drainage networks, and surface disturbance. Monitoring mine environments will require two basic information: baseline and change information. Baseline information pertains to information which future observations of the area can be compared with. Some of the environmental impacts of mining projects would be best indicated in change information.
Objectives
The objective of the study is to use straightforward image processing algorithms to generate change information from multitemporal data sets. The various methods are then evaluated for efficacy and suitability.
Materials and Methods
The following imagery were used: SPOT XS acquired 20 May 1998 and SPOT XS acquired 17 Decempber 1991. The overlap of the Dizon images cover images covers an area 16km x 12km with scene center located approximately at latitude 15°00' N and longitude 120°17'. Standard image processing procedures are employed. No attempt is made to devise new algorithms. Ground truth sources include a 1987 vertical air photo of the dizon minestite, government 1:50,000 topographic maps, a 1:250,000 land cover map plotted by the Swedish Space Agency in 1988, published geologic reports, company reports and other secondary sources. For the most part of the study, the PC-based ESIPP image processing system developed in the University of New South Wales was used.
Description of Study Area
The dizon Mines study area is on the western side of the southern portion of Zambales range and is bounded by latitudes 14°55' to 15°05' N longitudes 120°12 to 120°22' (see Figure 1). It covers an approximate are of 19,200 ha. The minestite lies of the western flank and is about 20 km south of Mt. Pinatubo whose eruption in 1991 caused heavy damage on equipment and facilities. The study area is drained towards the west by the Sto. Tomas and Santa Fe River. The former is fed by the Marella River, which drains the SSW slope of Mt. Pinatubo, and by the Mapanuepe River, which drains the catchment where the minestite is located.
Dizon is one of only two Philippine porphyry depsits inferred to possess an ophiolitic basement (Sillitoe and Gappe, 1994). Prior to the Mr. Pinatubo eruption, dizon Mines ranked as the Philippines' third largest copper and second largest by product gold producer, mining and milling 19,000 metric tons ore per day. The Dizon pit is oval in shape, about 1,3000 m across with a maximum width of 950m.
Average rainfall is 3,939 mm, one of the highest in the Philippines. Precipitation is characterized by extreme seasonality. December to April are extremely dry months and May to November extremely wet, with over 95% of total rainfall occurring during this period. Annual mean temperature is 27.1°C, January being the coldest (25.8°C) and may the hottest (28.5°C)
Lowlands are planted to rice, mango and coconut, and secondary crops like corn and vegetable. In the uplands, the indigenous Aeta propulation engages in swidden (slash-and-buran) cultivation, raising mostly root crops, corn and upland rice.
