EXTENSION OF HORIZONTAL CONTROLS USING STATIC GLOBAL NAVIGATION SATELLITE SYSTEM TECHNIQUE IN KWALE AND MOMBASA COUNTIES, KENYA

Abstract

Static global navigation satellite system (GNSS) surveys provide high positions accuracy by occupying a point for longer periods of time than kinematic systems. It includes a range of survey styles from rapid static surveys to continuously operating stations. This study sought to undertake survey data search for all the existing Survey of Kenya (SoK) old control pillars within the project area; identify appropriate sites for setting up new ground control (GCPs) pillars; monument the new GCPs as per SoK manual requirement and bserve the new GCPs, process and reduce observations to get their adjusted coordinates. Existing old control pillars within the project area were located using three topographical maps i.e. 200/2 (Kwale), 201/1 (Mombasa) and 201/3 (Ukunda). As per section I on survey marks of the SoK manual, eight appropriate sites were selected for new controls pillars and monumented. Two of the five dual frequency GNSS receivers were set up on two base stations and three were used to rove over the new controls for a minimum of one hour before moving them to other new points. The GNSS data was later downloaded, converted into receiver independent exchange (RINEX) format and processed using Leica Geo-Office 8.2 (LGO) GNSS software. The GNSS survey file was compiled as per section VII on presentation of computations of the survey manual and the coordinates of new points plotted in Form 3 as per section VIII on plotting of cadastral survey plan of survey manual. The survey computation file and the plan were forwarded to e director of survey for quality checks and authentication. Static differential GNSS technique provides best accuracy with reasonably low cost and time. The study recommends use of static differential GNSS technique in extension of horizontal controls for use in mapping, planning of land and future surveys since it gives high accuracy results.