Study on the update rate of correction message to reduce SA effect in DGPS mode

84-86<span style="font-size:14.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">The differential global positioning system (DGPS) is a typical use of the GPS, where the errors in measurement using GPS are calculated at a surveyed location and transmitted to the remote users within some specific geographic distance. The error due to the selective availability (SA), which otherwise cannot be removed also gets cancelled with the use of DGPS. The update rate of this correction message to the users is one of the factors governing the achievable accuracy of DGPS. This paper shows that the correction message remains valid only up to 5s to achieve high accuracy level in DGPS mode.