jgg     2014 34 (2):  51-54    ISSN: 0412-1961  CN: 21-1139/TG THEORETICAL RESEARCH ON NEUTRAL ATMOSPHERIC  REFRACTION INDEX School of Surveying & Land Information Engineering,Henna Polytechnic University,Jiaozuo 454003 Received: 2013-05-16  Revised: null  Online: 2014-04-21 Supporting info