Subsurface Maps and Illustrations %7 



bered north, beginning with township 1 at the international boundary. 

 All ranges are east and west of one principal meridian located in the east- 

 ern side of Manitoba. Guide meridians are spaced about 30 townships 

 apart and are numbered 1st, 2nd, 3rd, etc., meridians west. 



Figure 521 shows the numbering of sections in United States and 

 Canadian townships, and the subdivisions of the sections. Townships in 

 Canada, like those in the United States, are composed of 36 sections, each 

 approximately one mile square and containing 640 acres. The numbering 

 of the sections is shown in the figure cited. 



The Canadian system of designating the subdivisions of a section is 

 more convenient than ours. The 1/16 section (40-acre) tracts are num- 

 bered from 1 to 16 according to the Canadian plan of numbering sections 

 in the township. These subdivisions are called Legal Subdivisions, abbre- 

 viated Lsd. Thus, the shaded portion in the section diagram is described 

 as SW:i of Lsd. 12. According to our system the same tract is described 

 as the SWi of the SWi of the NWi or SW SW NW. The location of 

 a well situated at a is described as follows: SW SW NE SW| of section 

 10. In Canada the description (at h) is: SW SW Lsd. 6 of section 10. 



For a number of years it has been common practice in western United 

 States to make the footage location of a well according to multiples of 330 

 feet from surveyed land lines. Thus, a location described as 1650 feet 

 from the west line and 1650 feet from the south line of section 10 would 

 be in the SW SW NE SW 1/4 of the section, or the location of a in fig- 

 ure 521. 



Well "spotting" templets, made from acetate of about 0.020 inch 

 thickness, greatly facilitate the posting of maps. The templet is made with 

 inked lines corresponding to the land lines shown on the map, with holes 

 punched at the normal positions of well locations. The templet is regis- 

 tered over the land lines on the maps and the well is "spotted" by insert- 

 ing a sharp pencil in a hole at the correct location. 



Because of the fact that the surveying of public lands over the years 

 has not been carried out in a continuously systematic manner, there are 

 many duplications in the numbering of townships and ranges. Therefore, 

 in addition to the township and range, the state, and in some cases the 

 county, must also be known before a location on the map can be made. 

 For this reason, the state and county should be given in the location of 

 a well. 



Questions 



1. What is meant by the term, "subsurface map"? Upon what data is 

 this type of map prepared? 



2. What is the effect of crooked holes on datum elevations and inter- 

 preted dips? 



3. What is the effect of crooked holes on convergence interpretation? 



