《测圆海镜》的研究对象可用数学手段构造出来，因为所有问题都和圆城图式有关，未知量总是圆的直径，而已知量则是某些线段。
The object of study in Li Ye 's Ce Yuan Hat Jing ( 1248 ) can be constructed by mathematical means , because all problems in it are concerned with a diagram named " circular walled city " .
圆城图式