United States National Map Accuracy Standards

With a view to the utmost economy and expedition in producing maps which fulfill not only

the broad needs for standard or principal maps, but also the reasonable particular needs of individual

agencies, standards of accuracy for published maps are defined as follows:

1. Horizontal accuracy. For maps on publication scales larger than 1:20,000, not more than 10

percent of the points tested shall be in error by more than 1/30 inch, measured on the publication

scale; for maps on publication scales of 1:20,000 or smaller, 1/50 inch. These limits of accuracy

shall apply in all cases to positions of well-defined points only. Well-defined points are those that

are easily visible or recoverable on the ground, such as the following: monuments or markers,

such as bench marks, property boundary monuments; intersections of roads, railroads, etc.;

corners of large buildings or structures (or center points of small buildings); etc. In general what

is well defined will be determined by what is plottable on the scale of the map within 1/100 inch.

Thus while the intersection of two road or property lines meeting at right angles would come

within a sensible interpretation, identification of the intersection of such lines meeting at an acute

angle would obviously not be practicable within 1/100 inch. Similarly, features not identifiable

upon the ground within close limits are not to be considered as test points within the limits

quoted, even though their positions may be scaled closely upon the map. In this class would come

timber lines, soil boundaries, etc.

2. Vertical accuracy, as applied to contour maps on all publication scales, shall be such that not

more than 10 percent of the elevations tested shall be in error more than one-half the contour

interval. In checking elevations taken from the map, the apparent vertical error may be decreased

by assuming a horizontal displacement within the permissible horizontal error for a map of that

scale.

3. The accuracy of any map may be tested by comparing the positions of points whose locations

or elevations are shown upon it with corresponding positions as determined by surveys of a higher

accuracy. Tests shall be made by the producing agency, which shall also determine which of its

maps are to be tested, and the extent of the testing.

4. Published maps meeting these accuracy requirements shall note this fact on their legends, as

follows: “This map complies with National Map accuracy Standards.”

5. Published maps whose errors exceed those aforestated shall omit from their legends all

mention of standard accuracy.

6. When a published map is a considerable enlargement of a map drawing (manuscript) or of a

published map, that fact shall be stated in the legend. For example, “This map is an enlargement

of a 1:20,000-scale map drawing,” or “This map is an enlargement of a 1:24,000-scale published

map.”

7. To facilitate ready interchange and use of basic information for map construction among

all Federal mapmaking agencies, manuscript maps and published maps, wherever economically

feasible and consistent with the uses to which the map is to be put, shall conform to latitude and

longitude boundaries, being 15 minutes of latitude and longitude, or 7.5 minutes, or 3-3/4 minutes

in size.

Issued June 10, 194l U.S. BUREAU OF THE BUDGET

Revised April 26, 1943

Revised June 17, 1947