CHAPTER II 



SURVEYS AND MAPS 



INTRODUCTION 



KNOWLEDGE of the sizc, shape and characteristics of a territory, 

 such as is obtained by survey and mapping, is an essential 

 preHminary to further study. Of primary importance is the con- 

 struction of a correct framework on which to base mapping of 

 every kind in order that inconsistencies may be avoided. Such a 

 framework may be compared with the foundation of a house. 

 The three stages of survey, from the foundation to the smallest 

 detail of the finished building, are designated as geodetic, topo- 

 graphical and cadastral, terms which are used throughout this 

 chapter in the senses defined below.^ 



Since the requisite accuracy can now be attained with small 

 light theodolites, geodetic triangulation is much less costly than it 

 used to be. Base lines also have ceased to involve the large 

 expenditure of time and labour that they used to entail; they are 

 now measured swiftly and easily by a small party of men. Con- 

 spicuous examples of the advantages to be gained are provided by 



^ Geodetic Survey is concerned with the positions of certain series of points, that is to 

 say their latitudes and longitudes (or their co-ordinates on any other system) and their 

 heights. These points and the lines joining them constitute the framework. They are 

 fixed by means of baselines and triangulation of ist, 2nd or 3rd order, or a framework 

 by means of precise traverse when the terrain is unsuitable for triangulation, as in 

 country covered by heavy forest. Geodetic survey provides the foundation of all maps, 

 whatever their scales. 



Topographical Survey is concerned with features. It shows whatever is visible on the 

 ground, as for instance roads, railways and houses, and it will also probably show 

 major boundaries such as those separating different territories or administrative 

 divisions of a country. Topographical maps may either be 'small scale' which 

 includes scales from i :2,ooo,ooo (31-I- miles to i inch) to 1:250,000 (about 4 miles to 

 I inch), or 'Large scale' ranging from i : 125,000 (about 2 miles to i inch) to i 125,000 

 (about I mile to 2^ inches). 



Cadastral Survey is concerned with property boundaries which are often invisible 

 on the ground, and is frequently carried out with a view to the assessment of taxation. 

 Cadastral maps are seldom on scales smaller than i :5,ooo. 



