THIRD ORDER CONTROL EXTENSION BY TRAVERSING

ABSTRACT

Control is a précised position of reference monument to serve as the basis for orienting or checking the result of some other working methods. Due to scarcity of controls, local origin has to be established, posing a problem for charting and subsequent adjustment into the control network. Controls are needed so as to make cadastral, engineering and other lesser survey cheaper and faster to execute. This project is therefore aim atproviding such needed Controls (3^rd Order) at the Federal Polytechnic Adamawa. The control extension which started from Loko junction in Tamah, Adamawa in Adamawa L.G.A. of Adamawa state was tied to three existing government Controls (2^nd Order) and closed back at the starting point.  A total number of thirteen (13) controls points were established over perimeter Length of approximately 3.6km. Pro mark 3 GPS Receiver (dual frequency) was used for data acquisition. The result analysis shows that the established controls are very muchreliable. Control extension should be encouraged in area were they are notavailable in order to minimize or discourage establishment of local origin. In any community, non-availability of controls will hinder meaningful surveying operations.

CHAPTER ONE

INTRODUCTION

1.1 Background of the study

Ground control densification has gained some interesting developments as a result of the evolution of high-tech digital ground surveying equipment in the recent decades. Generally the efforts to bring in control across great distances using traversing has given way to the use of GNSS for speed and accuracy. On the other hand traversing between GNSS control stations to fill in controls over shorter distances is conducted with the total stations for accuracy purposes (Hill, 2008). The GNSS survey measurements result in point positions and thus the uncertainties in the measurements are positional factors of longitude and latitude, ellipsoidal height (λ, ϕ, h) or eastings and northings and elevation (E, N, el). Standards for GNSS surveys allow maximum uncertainties in horizontal positioning varying from 5mm + 5ppm to 10mm + 10ppm at 95% confidence level for the topmost class of control surveys depending on the use (Surveys Division, Arkansas Highway and Transportation Department (2013), Permanent Committee on Geodesy (PCG) (2014)). Over a distance of 3km uncertainties of 20mm and 40mm respectively will be allowed by these provisions. The import is that the relative precision of the azimuth between two such GNSS positions improve as distances between the points increase since the effect of the uncertainty on the line vectors is inversely proportional with length. And thus the position uncertainties distort the line vectors more over shorter distances. Control may be classified as an established precise position of reference monument to serve as the basis for originating or checking the result of some other working methods (C.D Ghilani & P. R Wolf, 2008). No meaningful development can succeed without adequate surveys. Also no registration of title over a landed property can be effective if cadastral surveys are not tied to controls. Such reliable controls are at present not available within the Federal Polytechnic Adamawa premises. Hence this project was initiated by me. This project is therefore aimed at providing such needed control points (3^rd Order) in this area. The establishment of these Controls will be very  useful to the Department of Surveying and Geoinformatics and other  practicing surveyors who might need them for various survey activities. A  total number of thirteen (13) control points were established over  perimeter length of approximately 3.6km. They were emplaced along  walkway of major roads within the project area.    The survey was tied to three identified existing government Controls (NSZ  056S, NSZ 057S and NSZ 058S) of 2^nd Order accuracy and closed back at the  starting point ( NSZ 058S )  The coordinate values of these controls are as shown on page 110. They were got from theMinistry of Lands and Surveys, Adamawa state. This network of controls was designed to conform to 3^rd Order standard.                                                                                                                          Pro mark 3 GPS dual frequency Receiver was used fordata acquisition.

1.2 PROJECT LOCATION

The project site is located in Tamah, Federal Polytechnic Adamawa,   Adamawa Local Government Area of Adamawa State. The project lies  within the Nigeria TOPO sheet 208 S.W (KEFFI S.W at scale 1:50,000.  The main stretch of the newly established Control network started from  Loko junction in Adamawa and terminated within the Polytechnic premises.  The project location is as shown via Google satellite image on page iv.

1.3    OBJECTIVES

With the Federal Polytechnic Adamawa sited at the out skirt of Adamawa main town, physical development will definitely trigger off lesser survey work like cadastral and engineering surveys that are essential for social economics development. Extension of controls to this area will provide an opportunity for Surveyors to assist other allied professionals in providing a sustainable and reliable development. For such lesser survey to be meaningful for the purpose for which they are carried out, they must  be tied to a main framework of controls. Also the project will provide an opportunity for the Department of Surveying and Geoinformatics, Federal Polytechnic, Adamawa to contribute meaningfully to the physical development of the Institution. The students in the department will also have free access to use these controls for their practical assignments. This will help to boost their practical knowledge at the early stage of their survey profession. Also the coordinate values of these established controls will be made available to the Ministry of Lands and Survey Adamawa state.

1.3    SCOPE OF WORK

The scope of work for this project includes the following:

i      Reconnaissance survey

ii     Baseline check using GPS receiver

iii    Monumantation

iv   Station description

v    Connection survey

vi   Station independent positioning using rapid static , post-

processed relative GPS positioning method.

vii    Data processing and Analysis

viii   List of coordinates generated

ix     Plotting and Presentation

1.4    SPECIFICATIONS

This project was executed according to specifications for third Order controls as contained in a text titled “Specification for Geodetic Survey in Nigeria” by Surveyors Council of Nigeria (SURCON), 2007 edition.   Table 2.0 below shows an extract from the text from page 44 -46 containing specifications for GPS relative accuracy.

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