LAND Kl'lClSTRAI loX 1\ M( »XAM I'.KJL'K. 419 



The Surveyor-Cieneral's Department obtained from that sci- 

 entific mission the fnndamental geographical data, the measure- 

 ments of bases, the directions reduced to the centre of all sides 

 of the triangulation olxserved from the geodetical station, and 

 with these elements the provisional values were calculated for 

 the geographical co-ordinates and distances to the meridian line 

 and to the trigonometrical points, for the region covered bv the 

 triangidation. 



In the general plan of the charts, these are separateh- organ- 

 ised by districts, as the absence of subsidies for the general trian- 

 gulation of the country made this restriction com])ulsory. 



Each one of these charts is theoretically divided into com- 

 partments (squares 40 kilometres wide) formed by lines parallel 

 to the central meridian, and its perpendicular to the crossing 

 point of that meridian with the medium parallel. 



The compartments are subdivided into sheets for qualifica- 

 tion, in the scale of 1 : 25,000, which, as a rule, is considered 

 normal, and is sufificient to show the relative position of the plots 

 granted and Government lands, and ultimately their division into 

 blocks reserved for concession on ([uit-rental or alienation by 

 sale, and, furthermore, through the assistance of the Agricul- 

 tural Department, they will show the generic classification of 

 the lands. 



Pro])erty in towns, villages, suburbs and other settlements 

 and all extremely sul)divided property is dealt with on a larger 

 scale in the detail charts. 



The topography of each estate and all its perimetrical con- 

 tour, as defined by rectangular co-ordinates referred to the origin 

 of local triangulation, is completed on the titles by the respective 

 plants and numerical identification as shown by its diagrams. 



We emplo}- the system of plane rectangular co-ordinates 

 which is more adaptable to the partial work of the cadastre, 

 within the limits of admissible error for the points most distant 

 from the origin of the co-ordinate axes. 



The projection of the charts is traced on the plane tangent 

 to a central point being the origin of the axes to which all points 

 of survey refer. 



For the current calculation of the transfer of the geo- 

 gra])hical position, transformation of co-ordinates, etc., the 

 dimensions of Clarke's ellipsoid were employed, these entering 

 in the numerical data of the various tables commonly used in 

 exjjedite geodesy. 



The first-class geodetical triangulation, covering the District 

 of Lourenco Alarques, permitted of the plan of the district being 

 made according to that triangulation to which is joined the sub- 

 sidiary and partial work of the network formed by the secondary 

 triangulation and traverses in part executed in a portion of the 

 district. 



