Fig 1. The schematic diagram of HELLO system.
A: location theory of surface locator; B: location theory of puncture locator; C: real practice of surface locator; D: real practice of puncture locator.
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.