Data compression method enables first order interpolator to operate at higher speeds. Method requires same number of additions and subtractions but fewer multiplications than the conventional method

Andrews, C. A.

English

NASA Technical Reports Server

August 1969
	 Brief 69-10291 
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. 
Improved First Order Interpolator 
.
The conventional data compression method de-
scribed in the literature (L.W. Gardenhire, "Redun-
dancy Reduction, the Key to Adaptive Telemetry," 
National Telemetry Conference, 1964; J. A. Bryan and 
J. W. Stumpe, "The Data Management Analyzer, A 
Laboratory Tool for Data Compression Analysis," 
International Space Electronics Symposium, 1965) 
requires the calculation of three slopes (a data slope, 
5, and upper and lower boundary slopes, U, L) for 
each data sample or point. The maximum rate at which 
samples can be accepted for processing using the 
conventional algorithm is limited by the relatively long 
times required for the calculations which entail three 
divisions, or multiplications, if a table lookup is used, 
for each data point. Although the multiplication time 
can be reduced by a special multiplier, its use would 
also increase the hardware weight and cost. 
An improved method, without the use of additional 
hardware, has been devised to enable a first order 
interpolator to operate at higher speeds. The data-
slope between the original data point and each succes-
sive data point is calculated as in the conventional 
algorithm. The upper and lower boundary slopes (U
and L) are then calculated by adding and subtract-
ing a constant from the data slope. This constant is 
obtained from a table lookup unit (which may be in the 
same memory as the other constants). The same 
number of additions or subtractions is needed in either 
the conventional or improved method, but the latter 
requires only one multiplication rather than three 
multiplications as in the conventional method. 
Note: 
Documentation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: TSP69- 1029.1 
Patent status: 
No patent action is contemplated by NASA. 
Source: C. A. Andrews of 
IBM Corporation 
under contract to 
Manned Spacecraft Center 
(MSC-1 1085) 
Category 02 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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Improved first order interpolator

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