MekongInfo Imagery/Base Maps/Earth Cover Documents This feed lists the 20 most recent Imagery/Base Maps/Earth Cover documents published on MekongInfo The Need for Metadata for GIS Data Layers and Products Thu, 17 Nov 2011 23:09:14 +0700 Assessing Mekong Aquatic Habitats from Space - Why the high-tech approach? Thu, 17 Nov 2011 23:08:04 +0700 An ArcGIS Tutorial Concerning Transformations of Geographic Coordinate Systems, with a Concentration on the Systems Used in Lao PDR A geographic coordinate system (GCS) provides a fundamental spatial framework to support the planning and development of a nation. All spatial data has a coordinate system and a GCS is a system that uses a three dimensional spherical surface to define locations on earth. In Lao PDR there have been several different geographic coordinate systems or "Datums" used, including Indian 1954, Indian 1960, Vientiane Datum 1982, Lao Datum 1993, WGS84 and the new Lao 1997. A GCS is often incorrectly called a datum, but a datum is only one part of a GCS. . When working with GIS or any other activity involving spatial data it is extremely important to understand these different systems and the relationships between them. . Poor understanding of these systems will most likely lead to great difficulties to combine data from different sources, difficulties in sharing maps with other centres or divisions within NAFRI, low map accuracy and overall inefficiency. If possible an organisation should try to use one standard geographic coordinate system or datum. . This document is intended to provide the staff at NAFRI the theoretical background about geographic coordinate systems used in Lao PDR as well as with a technical part describing and guiding people how to use the software ArcGIS as a tool to perform transformations. Thu, 17 Nov 2011 22:11:31 +0700