4 NEW HAMPSHIRE EXPERIMENT STATION [Bulletin 255 



A transit, plane table or staffhead compass and chain survey would 

 have been too expensive, and was unnecessary with this base map to 

 work from. Pacing seemed the only method of measuring distances 

 which fitted into the plan. By checking frequently to key points, the 

 map was found accurate to within two chains (132') and seldom more 

 than one chain (66 feet) in error. Any errors of more than one chain 

 were distributed so that the resulting error between points near to 

 each other was slight. 



The base map was laid off into blocks bounded by roads, brooks or 

 other clearly defined lines. These blocks were mapped in the order 

 which would give the most accurate results. Starting at a central 

 point the blocks were surveyed outward to the edge of the town in one 

 direction until a fan-shaped section was completed. Then, starting 

 again at the center, another sector was mapped. Within a sector, the 

 blocks were taken in the order which gave most opportunity to check 

 points on one block against those on another. The order was changed 

 in the field to fit the circumstances. 



The general plan within a block was to start from a known point on 

 the base map near one corner of the block, and map a strip down one 

 side of it, an eighth of a mile wide, then run one back beside that one, 

 a third beside the second, and so on until the block was mapped. The 

 "strips" were laid out entirely in the field, by pacing a zig-zag line 

 planned so that it came near all points such as wall corners, type lines, 

 brook intersections, buildings, etc., which were to be mapped. Running 

 from side to side of the strip was avoided except to insure careful 

 location of these points. When running a strip back beside one already 

 mapped, some shots were made to points already located to check the 

 accuracy, for there are bound to be errors in pacing, and frequent 

 checking makes it easier to locate them. 



This plan is well adapted to mapping solid blocks, especially as it 

 is flexible enough to allow for rearrangement to fit circumstances. 

 Where there were large fields, the lines could be run farther apart, but 

 in a section where the lots were small, the lines were closer. 



In the end, a block on the map would be found to contain several 

 major points to which the other important points were connected. If 

 these could be accurately located, either because there was no appre- 

 ciable error or because the errors balanced, no more field work was 

 necessary, and the rest of the map could be built around them. Other- 

 wise, a line had to be run connecting these major points and locating 

 them definitely. Once in a while an error made it necessary also to 

 locate lesser points, but usually the strips run in surveying were so 

 interwoven that it was not difficult to correct errors. 



A hand compass was used for direction, as any other instrument 

 would have been cumbersome, much slower and more expensive. 



The finished map was a mass of fine lines, small lots and small print- 

 ing, or the details could not have been shown. As a wall map it would 

 have been awkward to read, so it was made up in sections representing a 

 square mile each (eight inches square), drawn on 8^/2 x 11 paper, and 

 put in a loose-leaf notebook. In this form, special farms could be 

 referred to more easily, and if more than one sheet were needed the 



