Abstract
Recently, agricultural lands such as paddy fields, where cultivation was given up have been utilized as grassland for grazing or making hay. To manage such places skillfully, it is important to understand the area and how such fields are arranged. We therefore investigated arecently developed handheld GPS receiver (Garmin Corporation, eMap) to determine whether it could be used to survey the area and position of grasslands, and compared its use to the conventional glass fiber measurement tape. In the survey by GPS, the average errors which show a difference with a datum point were 1.18m and 0.63m, respectively at the time of a internal antenna and external antenna use. Moreover, the mean squared errors which show the variation in a survey value were 1.62m and 0.80m, respectively, based on the latitude and the longitude position coordinates. Thus, an external antenna raises the accuracy of a survey rather than an internal antenna. Although even in this case, the accuracy itself is not so high, the information about grassland shape, the area, and the perimeter distance were accquired with the same accuracy as measurements conducted using a tape measure. Furthermore, by using the GPS, we were able to obtain a survey map of the land where the target grasslands are widely dispersed from each other, in the same way as depicted by tracing aerial photographs. The hand held GPS receiver is also easy to handle and is a useful tool for acquiring rough information for practical grassland management.
