GPS in Laos.
There are many issues that need to be considered when collecting information with GPS receivers to ensure the highest possible quality of positioning data. This is particularly true when attempting to merge new GPS data with old data collected by other surveying and mapping techniques.
One of the most critical factors in data quality is understanding and accounting for different Datums. A "datum" is a combination of a mathematical model for the shape of the earth and a method of fixing that model to the actual earth so that points on the earth can be given mathematical coordinates. Hundreds of datums have been defined throughout the world and many of these have been modified several times as surveying methods improve and the defining parameters have been refined.
When working with GPS information it is critical to understand how each datum relates to the WGS84 datum (the default datum used by all GPS receivers). Geomap has developed a substantial body of knowledge in dealing with these issues in MapInfo GIS software, particularly in Laos.
We have also developed some solutions for dealing with unusual datums in Garmin GPS receivers. See our manuals for setup of Garmin GPS receivers for datums in Laos.
Lao Datum setup for Garmin eTrex