ALBERT

Description: Survey data from 2001 are given as 100 m ASCII grid file (ESRI format). All data are given in UTM (Zone 19H) coordinates. Laguna del Laja (Chile) is located at 36° 54' S and 71°05' W in the upper part of the Laja river basin in the Andean range at the east of Antuco volcano, at an altitude of 1360 m a.s.l. It is the largest and most important lacustrine system of the Biobío Region (Chile), with a watershed of ca. 975 km², the lake is fed by several small streams and is drained by the Laja river and two artificial tunnels for hydropower generation. The lake was surveyed in November 2001. The system used consisted of a Trimble GPS (4000 SSi, Fa. Trimble) connected by an echo sounder (EA400 Simrad). A special software was used to collect the data. About 160 cross profiles were measured within two weeks. The distance between profiles was 500 m in the main basin and 1000 m in the rest of the lake. At the beginning of measurements the water level was 1346 m above mean sea level. During the mapping campaign the water level rose 20 cm. The data were post-processed using the ARC/INFO TIN and GRID tools. A theoretical shoreline was digitized from topographic maps (scale 1:50.000) for the altitude of the dam overflow at the elevation of 1400 m a.s.l and was used as outer border line to the calculated lake depth model. The shoreline during campaign of survey was estimated from the digitized one and the end of the tracklines for the actual elevation of 1346 m a.s.l.. The resulting data were put into the GIS as xyz tripels to produce a TIN (trianguleted irregular network). With help of the TIN different raster maps were generated.