Alberti invent this instrument, which consists of two parts, the horizon and the spoke. It can provide an accurate and easy way of drawing the map of Rome. The map that the instrument produces will consist of several layers of information including: walls, river, streets, temple, public works, gates, and habitable buildings.
The “horizon” is the circle which the depiction of the city is enclosed, and the circle is divided by 48 degrees and each degree is divided into 4 parts, called “minutes”. The “spoke” is the length of radius of the horizon, the spoke is divided into 50 parts with each part is divided into 4 minutes.
Once the instrument is complete, we then can check the table provided and plot the points given. “Corner” is the drawn angle created by the intersection of two lines. “Apex” is the furthest point of the curvature and the curving back from that “apex” which the curved line makes in its passage.
I marked each category in different color and each significant monument/building was assigned with a number which indicated at the back of the instrument.