Preparation of Engineering Soils and Drainage Survey Strip Maps from Aerial Photographs

This paper reports the procedure for preparing engineering soil and drainage strip maps of proposed highways from aerial photographs. These maps are prepared from uncorrected aerial photographs at a scale of approximately three inches to the mile. An approximate scale is used, since ground control in conjunction with rectified airphotos would greatly increase the cost of preparing the strip maps. The use of aerial photographs as an aid in highway engineering is rapidly increasing. Since many preliminary location surveys are made from airphotos, the advantage of identifying the soil and locating drainage structures from these same airphotos would greatly reduce the cost of preliminary surveys because objectionable sites could be avoided. Strip maps of a highway location showing areal extent of soils and the probable profile development would benefit soils engineers in planning soil surveys and securing representative samples. These strip maps can be prepared economically from aerial photographs that are available at a nominal cost throughout the United States. IN T R O D U C T IO N The object of a soil and drainage survey of a proposed highway is to obtain information on soil conditions and watershed areas of drainage systems as they exist in the field so that a highway can be located and designed economically. There are several sources of in­ formation available to the engineer for a preliminary analysis of an area where a highway is proposed. In most instances, the information is of a specialized nature which was prepared for other than engineer­ ing purposes.