Oehman's survey instrument

Oehman's survey instrument

[′ā·mənz ′sər‚vā ‚in·strə·mənt]
(engineering)
A drill-hole surveying apparatus that makes a photographic record of the compass and clinometer readings.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.