GMT/local-time conversion is made by a longitude pocket instrument that automatically indicates desired information by simply manipulating the moveable portion of the instrument in accordance with a set of simple instructions imprinted on the reverse side of the instrument

Creveling, C. J.

English

NASA Technical Reports Server

GMT/LOCAL-TIME
CONVERSION BY LONGITUDE 
DESIGNED IT C. C1EVELING 
1. TO FIND LOCAL-TIME, oivEpi GMT & LONGITUDE 
• SET G ON MOVEABLE CIRCLE TO GIVEN GREENWICH 
TIME ON FIXED LOCAL-TIME SCALE. 
• OPPOSITE GIVEN LONGITUDE ON MOVEABLE CIRCLE, 
READ LOCAL-TIME ON FIXED SCALE. 
• FORMULA IS TLOCAL
	
GMT + LONGITUDE Is 
2. TO FIND GMT, GIVEN LOCAL-TIME a LONGITUDE 
• SET GIVEN LONGITUDE ON MOVEABLE CIRCULAR 
SCALE TO LOCAL-TIM	 N FIXED SCALE. 
• READ GMT FROM FIX	 CALl AT G(GREENWICH) 
INDEX ON MOVEABLE SCALE.
LONGITUDE 
.FORMULA IS GMT T LOCAL -	 15 
3. TO FIND LONGITUDE FROM GMT A LOCAL-TIME 
is SET G ON MOVEABLE SCALE OPPOSITE GIVEN GMT 
ON FIXED SCALE. 
• READ LONGITUDE ON MOVEABLE SCALE AGAINST 
GIVEN LOCAL-TIME ON FIXED SCALE. 
• FORMULA IS LONGITUDE = 15 (TLOCAL -GMT) 
On 
/
December 1967	 -	 Brief 67-10548 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
GMT/Local-Time Conversion Chart 
GMT/LOCAL-TIME CONVERSION BY LONGITUDE 
NOON 
13	 12
14 10
-75 90 is 
I 
is
29
': 
22 2
23	 24 1 
MIDNIGHT
The problem: 
In the calculation of local time, Greenwich Mean 
Time (GMT), and location by degree of longitude, 
navigators in the past have had to determine two 
of the factors in order to ascertain the third. While 
this is done in a straightforward manner, using rela-
tively simple formulae, it consumes appreciable time 
and is inconvenient in the case of fast-moving trans-
portation media where the operator of the transport 
must interrupt his normal operational routines. 
The solution: 
A GMT/local-time conversion by longitude pocket 
instrument that automatically indicates the desired 
information by simply manipulating the moveable 
portion of the instrument in accordance with a set of 
simple instructions imprinted on the instrument's re-
verse side.
continued ocrlcaI) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19670000547 2020-03-11T20:59:14+00:00Z
Notes: 
I. While this device has been designed to aid NASA 
personnel in quick-look evaluation of a given 
satellite's reported position in relation to the 
STADAN (Satellite Tracking and Data Acquisi-
tion Network) stations, its polar projection map 
makes it an ideal tool for instructing students in 
the time/longitude relationship of easily ' identified 
terrestrial points and areas. 
2. The device should be useful to operators of high-
speed aircraft which must respect and avoid inter-
national boundaries.
3. Inquiries concerning this invention may be di 
rected to:
Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B67-10548 
Patent status: 
Inquiries about obtaining rights for the commer-
cial use of this invention may be made to NASA, 
Code GP, Washington, D. C. 20546. 
Source: Cyrus J. Creveling 
(GSC- 1052 1)
. 
-01, 
Brief 67-10548 ,	 Category 01


GMT/local-time conversion chart

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