The modern digital theodolites have electronic displays. Other purchases included octant, equatorial, two theodolites, 10-foot sextant. Later surveys used more compact theodolites. Fennel Kassel and others later produced gyro attachments that can be mounted on normal theodolites. McMinn traced maps from "Bengal" and stowed two theodolites and several pocket-compasses. Levels and theodolites would have slightly different reticles. Directors could also be used instead of theodolites for artillery survey over shorter distances. The accuracy reaches from 0.2" (theodolites, small astrolabes) to 0.01" (modern meridian circles, Danjon). Theodolites and levels are often used by constructors rather than surveyors in first world countries. High-accuracy transits or theodolites were used, and angle measurements repeated for increased accuracy. By the early 19th century, Europeans preferred theodolites to circumferentors. Theodolites were later adapted to a wider variety of mountings and uses.