September 7, 2009
- Featured Maps
- September 7, 2009
Giovanni Maria Cassini was a noted geographer, engraver, and publisher in Rome. He was one of the last of the fine Italian globe makers active at the end of the 18th century. Cassini made Terrestrial and Celestial Globes in 1790 and 1792. He also published the twelve terrestrial and twelve celestial globe gores that formed these globes in his atlas "Nuovo Atlante Geografico Universale" along with rules for the construction of globes and globe gores.
The full title of the Terrestrial Globe is Globo terrestre / delineato sulle ultime osservazioni con i viaggi e nuove scoperte del Cap. Cook, inglese ; Gio. Ma. Cassini C.R.S. inc. Roma : Presso la Calcograf[i]a cam[era]le, 1790. The globe shows contemporary discoveries in the Pacific as well as the routes of three of Captain James Cook's voyages.
Cassini's terrestrial globe gores were used to create a physical globe about 34cm in diameter. In the virtual world, we have scanned the gores, georeferenced them and then projected and wrapped them on a three dimensional globe shown in the two images below - clicking on the globe image will open the globe in Google Earth (plugin required, turn off Atmosphere layer in Google Earth).
The terrestrial globe gores are shown below in their original printed form on four sheets of three gores each. The images of the sheets were downloaded from the Library of Congress, Geography and Map Division.
The gores were then trimmed in Photoshop and georeferenced in ArcMap to the WGS 1984 coordinate system as shown in the image below. This is the image that is used to create the virtual globe in Google Earth and ArcGlobe. Clicking on the image will open it in Rumsey Google Maps, in a Mercator Projection.
Terrestrial and Celestial globes were often paired together so in 1792 Cassini made a companion Celestial Globe, showing the Heavens and all the known stars and constellations. The Celestial Globe's full title is Globo Celeste calcolato peril corrente anno sulle osservazioni de Sigg. Flamsteed e de la Caille. Roma : Calc(ografi)a Cam(era)le, 1792. Inciso dal P. Gio. Ma. Cassini, C.R.S. Like the terrestrial globe gores, the celestial gores were scanned and georeferenced and then placed on a virtual globe as shown below. Click on the globe image below to open the globe in Google Earth (plugin required, turn off Atmosphere layer in Google Earth).
Since the Terrestrial and Celestial Globes were typically viewed side by side in their physical instantiations, we wanted to join them together in their virtual copies. We were able to do this in Google Earth by turning the Cassini Celestial Globe inside out and placing it 64 million meters outside the Terrestrial Globe, as seen in the video below. The same space can be viewed live in Google Earth (plugin required, turn off Atmosphere layer in Google Earth).
At the time we did the Cassini Globes project, the Rumsey Collection did not have copies of the Cassini globe gores. The Celestial Globe gores as well as copies of the Terrestrial Globe gores were added to the Rumsey collection in 2007. The Terrestrial gores are the same issue as the Library of Congress copies, but the coloring is different, as can be seen from the images below, in a slide-show from the Rumsey collection database, which includes the gores and the printed parts for the "ring sheet" of zodiacs and 2 polar calottes (caps). Use the arrows to advance the slides; click on the little "i" to view the catalog record; click on "Go to Source" to see the slide-show full screen.
Taking the virtualization of the Cassini globes a step further, the Cassini Globes have been placed on the Rumsey Map Islands in the virtual world, Second Life. As shown in the video below, David Rumsey's avatar, Map Darwin, explores the virtual globes which are over 100 meters in diameter and placed next to each other on the map islands, floating above an 1883 map of Yosemite Valley.
Finally, as shown in the video below, it is possible to combine the Cassini Terrestrial Globe with other GIS layers, including NASA's satellite image of the world at night, several satellite images of world topography and bathymetry, and other historical maps and globes.
Perhaps Giovanni Maria Cassini would be intrigued to see his Terrestrial and Celestial Globes take on new life in the 21st century digital world, all firmly based on the great accuracy of his geographic knowledge and the high quality of his engraving skills.