Identification of Feature Details in Land Extents Using Handheld GPS

Research Officer, Center for Research & Development, Geographic Information for Strategic Defence Applications BSc Hons (SLIIT) Chartered Civil Engineer, Department of Civil Engineering BSc Eng. Hons. (Sri Lanka), PG.Dip (Moratuwa), M.Eng. (Tokyo), D.Eng. (Tokyo), MICE (UK), FIE (SL) Director, Engineering Service Board BSc Eng. (Sri Lanka), MBA (Colombo), MSc (Geoinformatics/Netherlands), Ph.D (Netherlands), C.Eng, MICE (UK), FIE (Sri Lanka) Handheld GPS equipment are becoming affordable and vendors are presently loading them with additional features such as easy data capture, data transfer, easy tracking and analysing capabilities. In order to ascertain the mapping capability using handheld GPS, a case study application was carried out mapping a known land extent and its features using several handheld GPS units of the same make and having same parameters. The mapping exercise was carried out by trained GPS operator groups who surveyed the same area approximately at the same time. GPS survey data were plotted on the served map of the project area which is a land extent of 6.6km2 close to Homagama. Surveys were carried out measurements with varying spatial resolutions. Survey results indicate the issues faced by the GPS operators when maps were prepared with measured data. Results and discussion attempts to enlighten GPS users of the limitations pertaining to mapping and also the accuracies of the present paper associated. The survey used Garmin GPS 12 and Magellan 600 handheld units. Results and accuracies of two or more units when operated parallely are discussed in this paper. Common problems such as signal coverage in the open and under canopy, plotting capability of smaller features to an acceptable level are also discussed. This work was limited to the measurements made in the horizontal direction and therefore no attempts were made to measure elevations