Mapping of Granite Quarries in Kerala

About the mapping initiative

Introduction

The transformation of granite stone, from a protective wall or a primitive weapon of prehistoric human being to commercial granite, (Phanerocrystalline, compact, hard and polishable, decorative building rock) a mining product have at least 7000 years of history as a resource used by man. Granite mining extract the common property of the present and future generations of not just man, but other organisms as well, while helping the building up of human civilisations. Across the countries, there exists wide variation in the manner in which granite quarrying in conducted. In developed countries it has evolved into a formal enterprise using techniques like GIS, remote sensing, 3D visual impact assessment etc. to foresee the impacts (Ramos & Panagopoulos, 2004). The data regarding the projects is made available for public review. On the other hand, the small-scale mining sectors of most developing countries are still in its infancy in terms of formalization, use of advanced technology, prior assessment of environmental impact, professional management and public review process.

In Kerala, the southern west state of India which harbour 18 % of the Western Ghats Taluk with high endemic and biodiversity rich regions, the information we have on the granite quarries is the low resolution maps with point representation of mining site in some districts of Kerala prepared by mining and geology Dept of Kerala and published as Mineral information system through its official website (http://dmg.kerala.gov.in). As observed by the FIMI report (1994), there is a big information gap at the national or state level, in the collection of spatial and temporal information on small scale mechanised and non- mechanized quarries. However, developments in Geographic information technology (GIT) which combines GIS, Remote Sensing and GPS has created new avenues in mapping and spatial decision making. After the advent of FOSSGIS and Web GIS, GIT has simplified the process of data availability in public sector, analytical capability and peoples’ participation in mapping and spatial decision making

The present study attempted to map the distribution of granite quarries in Kerala using the open access satellite data during period 2014 - 2015 from WebGIS sources like Google Earth, Google Map and Bing Map. Manual visual interpretation, area estimation and analysis were done using QGIS. Primary proximity analysis of the quarries was also done using available valuable secondary geographic data. The methodology adopted for the work is critical mapping which explicitly addresses the various sets of decisions taken during the mapping process as a function of existing power relations embedded in knowledge (Crampton, 2010). Rather than a standalone map of granite quarries, our interest was to see the distribution of quarries in relation to major landscape features.

Methods

The GPS coordinate, area and elevation of the some quarries were recorded using Garmin Oregon 650 GPS. The GPX layer file format in GPS was converted to Keyhole Markup Language (KML) file format and Shape file (.shp) format for further analysis which are the common file format in Google earth and GIS software respectively. The pattern and visual specification of the quarry was verified using these KML file in Google earth software using recently available (2014 – 2015) google satellite image of the site and its historical image. Further verification was done by google map and Bing map using QGIS - Open layer plug-in. Using these visual specifications we manually interpreted and vectorised all quarries in Kerala as polygon shape file layer and verified with detailed field visit of selected granite quarries. Each quarries in a district were named with unique id in DTVQN system in which D indicate district code, T for Taluk code, V for village code and then QN indicate Quarry number.