The coordinates are the angle from the GZ zero line (in torans) which goes from the GZ through the center of Kerath's Arch, the horizontal distance from the GZ (in spans), and the elevation in reference to the GZ (in spans). The GZ observation pod is at the 0 elevation point so most locations in the Cavern are below that level.
Converting everything gives the following:
The Uran District (later renamed D'ni-Ashem'en) and we know as the ErcanaCitySilo, is approximately 11deg clockwise of the zero line running from the GZ through the center of Kerath's Arch. It is about 3.95 miles from the GZ and about 2173 feet below the level of the GZ. It is further out than both Bevin and Kirel and probably is in another smaller cavern.
In comparison, Bevin is almost 13 deg counterclockwise from the zero line, at a distance of 2.5 miles and about 950 feet below the level of the GZ.
Ferry landing and the lake are 1240 feet below the GZ which makes it lower than Bevin but higher than the silo. (I could never figure out how dropping pellets in the Silo did any good since the lake is so much higher...)
For backgorund: In 5359 DE, King Me'emen ordered the contruction of a new industrial district, Uran, to replace Nehw'eril. Contruction actually began in 5475 DE. About a year after the death of his only son, about 5541, Me'emen change the name to Ashem'en to honor his son.