The Geoglyphs of San Ignacio - New Results from the NASCA Project
Abstract
We report about the current state of our Nasca project. The block Sacramento (called Palpa in earlier publications) is fully processed and the block San Ignacio is almost completed. We show the results of San Ignacio, which were obtained through the processes of photo triangulation, DTM measurement, orthoimage and orthomosaic generation and 3-D vector extraction. High quality photorealistic visualizations of the terrain and the geoglyphs are already available. The next task will be the integration of the data on a GIS platform.
Introduction
The geoglyphs of Nasca, Peru, are considered one of the world's major mysteries. Despite the fact that many efforts have been made in the past 70 years to record and analyze the geoglyphs no convincing explanation has emerged yet which would explain the purpose of these drawings in the sand beyond any doubt. Many hypotheses have been put forward and each author will find a certain number of lines and figures in support of his/her opinion. The huge number of lines, trapezoids, star centers, biomorphic figures, etc. has up to now defied any comprehensive recording and analysis.
We are currently conducting an ambitious project which aims at the complete 3-D recording of the geoglyphs of the areas of Nasca, Sacramento and San Ignacio (a total of about 300 km2) with photogrammetric means. This is done in cooperation with a group of archaeologists who will try to relate their excavation results to the geoglyphs in order to get a more complete picture of the overall cultural and social background of the Nasca people (200 B.C. - 600 A.D.).
We are using the latest digital photogrammetric technology for the recording of the geoglyphs and some of the most advanced visualization software. Finally, all data will be integrated on a GIS platform, which will require the efficient management of both vector- and extensive raster image data.
We have aquired over 1000 aerial photographs at scales 1:5 000 and 1:10 000 both in colour and B/W. In addition we have collected existing, older photographs which can give us an indication of the damage that has been done to the geoglyphs in recent years.
The block Sacramento has been fully processed and visualization results have been shown to the public on a SGI Onyx2 in an interactive mode at the Nasca exhibition in the Rietberg Museum, Zurich and in the VisDome of ETH Zurich as stereo projection on a large 4 x 12 m2 screen and on other occasions. For details on the complete project (motivation, goals, data acquisition, processing and visualization of the Sacramento block) we refer to Grün, et al., 2000.
In this paper we report about the ongoing work on the San Ignacio block. Here we have only B/W images available for processing. The phototriangulation has been performed on an Analytical Plotter, since automated triangulation does not deliver the desired results. The DTM has been measured completely in manual mode, because of the high quality requirements. Digital orthoimages have been produced over the largest part of the area and a mosaic has been generated. This is the basis for photorealistic visualization. A number of geoglyphs have been measured in the stereomodels in vector mode (so far we have included about 6 700 vectors in the dataset), but this work is not finished yet.
Photoriangulation
Figure 1 shows the location of the three blocks Sacramento (in earlier publications called "Palpa"), San Ignacio and Nasca, which are also processed in this sequence. A detailed layout of the triangulated part of the block San Ignacio is given in Figure 2.
Figure 1: Location of the blocks Sacramento, San Ignacio, Nasca in southern Peru
