try. The observer takes his post upon a building or other elevated point, reads distances by the range finder and directions by a prismatic compass. It is simply the stadia method without the rodman. The use of polar co-ordinate paper, as shown in Fig. 9, is a great aid to rapid plotting.
Plotting Stadia Notes. Chas. R. Thomas is author of the following, published in Engineering News-Record, June 28, 1917:
By plotting stadia notes on separate sheets such as are shown in Fig. 10 and tracing the finished map from these sheets, the cost of plotting stadia notes has been materially reduced and the speed almost doubled. Plotting topography by this method becomes independent of drafting-room equipments, a lead pencil being the only tool required.
The method of procedure is to sketch the topography in heavy pencil lines and either paste the sheets together for the draftsman or send them to him separately. The sheets are placed under the tracing cloth, and the finished tracing is made directly from them. The paper used for ordinary work is 8% x 11 in. in size. Using a scale of 100 ft. to the inch, a length of 1,000 ft. and a width of 600 ft. of topography may be plotted on each sheet. Topography may be plotted by surveyors on rainy days, either in the field or in the office, several men working independently on separate parts of the notes. It is remarkable how much the use of a graduated paper speeds up the interpolation of contours and increases the accuracy of scaling.
Reconnaissance Mapping. Fig. 11 and the following short quotation from an article in Engineering and Contracting, April 29, 1914, show how admirably decimal rectilinear charts may be adapted to preliminary survey work.
In mapping the reconnaissance work the drawings were made to conform as nearly as possible to the working plans for the finished road. By doing this they showed the more essential features, such as profile, alignment and drainage of the road, and were more easily handled by the officials to whom they were submitted.
A fair sample of this portion of the work is shown in Figure 11—a portion of the reconnaissance made in Clare county. The small sketch shows the routes followed. In this county there were several different roads which could be taken and used as a portion of the trunk line highway. The heavy line shows the one in preference. These maps were drawn to such a scale (1,000 ft. to an inch) that ten miles of road could be conveniently placed on a sheet 20 x 36 ins. in size. The width of the road was exaggerated in order that such things as cuts, fills, ditches, etc., occurring within the limits of the road could be shown clearly. All information gathered was placed on, or adjacent to, the plan of the road except the profile, which was shown below.
Zones. Polar charts are especially useful for mapping of zones, such as fare zones with respect to a central point, residence zones, population density zones, etc. An example is shown in Fig. 12, taken from Electric Railway Journal, which gives the rush hour passenger traffic outbound from the one-mile zone, the width of the black lines showing relative number of passengers carried.
Chart of Angles. Fig. 13 by IT. Hodgkinson, printed in American Machinist, January 16, 1919, shows a use for polar paper which would