These limits apply to positions of such well-defined points as roads, monuments, large structures, and railroads that are readily visible and can be plotted on the map within 0.25 mm of their true positions. Standards for vertical accuracy require that not more than 10 percent of the tested elevations be in error by more than one-half of the contour interval. Because of the prescribed standards of accuracy, topographic maps published by different agencies differ little. Some variation may be noted in format, scales, sheet boundaries, and classification and selection of planimetric detailvariations due primarily to the need to meet specific requirements. Standard topographic maps are published in quadrangles bounded by lines of latitude and longitude.
Scale varies with topography and contour interval.
The smaller scale maps are useful as the bases for general soil maps, for reference, and for schematic soil maps. Topographic maps can be used as the base for detailed mapping if recent large-scale maps are available for the whole survey area. The accuracy of standard topographic maps gives them definite advantages in measuring distances and directions. The topographic pattern is helpful in understanding soil and studying drainage, irrigation, and hydrology. The detail on the maps relieves soil scientists of part of the task of recording the location of ground features while mapping.