Horizontal Accuracy Standards for Geospatial Data

Some of the highlights of the new ASPRS Horizontal Accuracy Standards for Geospatial Data are the following:

1. Unlimited horizontal accuracy classes:
   The new standard was designed to fit any horizontal accuracy requirement no matter what technology, current or future, is used. Table 3 represents the new ASPRS horizontal accuracy classes.

   Table 3 The new ASPRS horizontal accuracy classes

   Horizontal Accuracy Class	Absolute Accuracy RMSEH (cm)	Orthoimagery Mosaic Seamline Mismatch (cm)
   # cm	≤ #	≤ 2 × #

    

   RMSE_H = RMSE_x² + RMSE_y²

   RMSE_H = Radial RMSE = Circular RMSE = Two−dimensional RMSE of X & Y

2. Aerial triangulation results should be twice as accurate as the generated products:
   1. Ortho and planimetric maps ONLY:
      • RMSE_H(AT) = ½ × RMSE_H(Map)
        and
      • RMSE_V(AT) = RMSE_H(Map)
   2. For ortho, planimetric maps, and elevation maps:
      • RMSE_H(AT) = ½ × RMSE_H(Map)
        and
      • RMSE_V(AT) = RMSE_H(DEM)
3. Control points for aerial triangulation should be twice as accurate as the generated product:
   1. For ortho and planimetric maps ONLY:
      • RMSE_H(GCP) = ½ × RMSE_H(Map)
        and
      • RMSE_V(GCP) = RMSE_H(Map)
   2. For ortho/planimetric maps and elevation maps:
      • RMSE_H(GCP) = ½ × RMSE_H(Map)
        and
      • RMSE_V(GCP) = ½ × RMSE_V(DEM)

Table 4 lists common horizontal accuracy classes for geospatial mapping products.