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View the Sun Dagger Explorer
a demonstration of the Interactive Model, adapted for museum installation
at the New Mexico Museum of Natural History and Science


Sun Dagger Interactive Model

an archival restoration and a research tool

The Solstice Project is proud to announce a breakthrough Interactive Computer Graphics Model of the Sun Dagger Site in Chaco Canyon, an astronomical site of the ancestral Pueblo Indian culture.  Representing 20 years of research and three years in production, the model is an archival restoration of a thousand year old calendrical site that marks the solar and lunar cycles. The model’s interactive tools offer opportunities to analyze the astronomical functioning of the site and to explore how it was originally developed.

At the Sun Dagger site, the Chacoan people commemorated the cycles of the sun and the moon in light patterns cast by rock slabs onto spiral rock carvings. Through state of the art technologies and with an outstanding team of photogrammatrists, a geodecist and computer modelers, the Solstice Project achieved its goal of archival digital restoration of the site. (In 1989, the Project found that the rock slabs had shifted and the light markings on the petroglyphs had been significantly disturbed.)

We are particularly excited that, in addition, the interactive capability of this computer model offers dynamic opportunities for scientific exploration of the site. One can navigate around the 3- D model, observing it from any angle, set the calendar date and time of day for positioning the sun and moon, projecting shadows of the stone slabs onto the cliff and spiral patterns in real time.
The slabs and the spirals can be adjusted in their positions and shapes. The student or scholar is in essence in the role of a Chacoan astronomer, testing the sensitivity of the elements of the site and assessing what actions may have been taken by the Chacoans to precisely mark the sun and the moon. In these images the model accurately replicates the summer solstice sun dagger. The colored lines indicate certain interactive movements that can be done with the model.

The scholars behind the making of the Sun Dagger model over many years include:

Anna Sofaer, president of the Solstice Project has coordinated since 1978 the Project’s interdisciplinary astronomical research and preservation efforts with the Sun Dagger site.  Their work included ongoing mapping and surveying efforts since 1979 to record the fragile slabs and spirals, as well as extensive photo documentation of the site’s solar and lunar markings. These efforts finally culminated in the precise digital restoration of the Sun Dagger in 2006.

Phillip Tuwalststiwa, a geodecist and member of the Hopi Tribe, gave his early support and participation in the model building at the Center for Mapping of Ohio State University.

James Holmlund, president of Western Mapping developed the laser-scanned model of the Sun Dagger site in 2006.

Andrew Piscitello, president of Aero-Metric Company, developed the 1984 photogametric model of the Sun Dagger site in 2006.
William Stone, National Geodetic Survey of NOAA, made a precise astronomical survey of the Sun Dagger site essential to the model’s accurate replication of its solar and lunar markings.
Alan Price, Associate Professor, the Advanced Computing Center for the Arts and Design, Ohio State University, tested the model with astronomical programs and created the interactive model with extensive research tools.

The above material is copyright 2007, Solstice Project, all rights reserved.

For background and research papers of the
Solstice Project see our website:;
for particular reference to the Sun Dagger, see:

Sofaer, A., V. Zinser, and R.M. Sinclair. 1979. “A Unique Solar Marking Construct.” Science 206:283-291.
Sofaer, A., R.M. Sinclair, and A. Doggett. 1982. “Lunar Markings on Fajada Butte, Chaco Canyon, New Mexico.”
In Archaeoastronomy in the New World, ed. A.F. Aveni, 169-181. Cambridge: Cambridge University Press.
Sofaer, A., and R.M. Sinclair. 1987. “Astronomical Markings on Three Sites on Fajada Butte, Chaco Canyon,
New Mexico.”
In Astronomy and Ceremony in the Prehistoric Southwest, ed. J. Carlson and W.J. Judge Jr., 13-70.
Albuquerque: Maxwell Museum of Anthropology.
Palca, J. 1989. “Sun Dagger Misses Its Mark.” Science 244: 1538.

All material on this site is © 2016 The Solstice Project