V. MAPS, ETC. 679 



In the year 1863, the survey of the entire territory was commenced in 

 connexion with the survey of the city for the Doomsday Book (land registry), 

 and concluded in the year 1868. The additional triangulation work required 

 for that purpose, which was commenced simultaneously with the divisional 

 survey, was connected with the already determined trigonometrical points of 

 the town, and then with the base of Holstein. The number of trigonome- 

 trical points amounts to 1663, and the station points among the same, 993 

 in number, have been marked, with a very few exceptions, by granite pillars 

 sunk into the ground. The angles were repeatedly measured by means 

 of an 8-inch theodolite ; the trigonometrical net corrected and adjusted 

 according to the method of least squares, which was followed by the calcu- 

 lation of the horizontal rectangular co-ordinates, from which the geographical 

 position was deduced by a very simple method. As origin of the system of 

 co-ordinates, the spire of the large St. Michael's Church had already been 

 fixed upon, and its geographical position determined as follows : 



Latitude = 53 32', 55.7" 

 Longitude E from Greenwich = 9 58', 41.75". 



The bailiwick of Bergedorf, formerly belonging to the joint jurisdiction of 

 Hamburg and Liibeck, having been incorporated with the territory of Ham- 

 burg,;; the ^survey was extended to this area ; and for this district a new 

 division of survey sheets was adopted since the introduction of the metre 

 standard. 



The scales employed in drawing the maps are: 1:250, and 1:1000; for 

 the new division of the sheets 1 :200, 1 : 500, and 1 : 1000. Exact levels are 

 given all over the entire territory, and bench marks are durably established 

 in sufficient number. Connected with these, special levelling will be 

 carried out by means of distance and altitude measurement. 



In the adjoining parts of the territory not belonging to Hamburg, so far as 

 such is still made use of for the maps to be published, levels will be taken 

 by means of aneroid barometers. 



The reduction of the survey sheets is effected by means of a specially con- 

 structed pantograph. 



The 'multiplied copies will be published in scales of 1:1000, 1:4000, 

 1:20,000, and 1:50,000 (32131) and c), by O. Meissner and Behre, in 

 Hamburg. 



According to the directions given in the plates for the distance and the 

 altitude measurements, the latter will be executed by the tachymeter, 3O79a. 

 An ordinary levelling staff, divided into centimetres, will be employed for 

 the purpose. A survey field book illustrates the work actually executed for 

 a portion of the bailiwick of Bergedorf. 



The co-ordinates of the station points required for levels will be calculated 

 from, those of known trigonometrical points, or from the polygon points of the 

 detail survey, and entered in the survey sheets. In the principal polygons the 

 distances between the station points will be measured with chains, or sheet- 

 ribbons, and the altitudes determined by levelling. A synoptical table of 

 results obtained by distance and altitude measurements, with the directly 

 executed longitudinal measurements and with the geometrical levellings, is 

 given. It should be mentioned that this work was executed in November 

 1874, in unfavourable weather, and that more satisfactory results are ob- 

 tainable by this method. 



When the station points have been plotted on the survey-sheets, and the 

 levels of the altitude points have been calculated from the field book, these 

 latter are plotted on tracing paper, containing the sheet divisions, the station 

 points, and more or less the situation of the respective survey-sheets. For 

 plotting the altitude points a transferrer is used, made either of metal or of 



