PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
July 2015
533
Table 6. Recommended Number of Checkpoints Based on Area
Project Area
(Square
Kilometers)
Horizontal Accuracy
Testing of Orthoimagery
and Planimetrics
Vertical and Horizontal Accuracy Testing of Elevation Data sets
Total Number of Static
2D/3D Checkpoints
(clearly-defined points)
Number of Static
3D Checkpoints
in NVA
Number of Static
3D Checkpoints
in VVA
Total Number of Static 3D
Checkpoints
≤500
20
20
5
25
501-750
25
20
10
30
751-1000
30
25
15
40
1001-1250
35
30
20
50
1251-1500
40
35
25
60
1501-1750
45
40
30
70
1751-2000
50
45
35
80
2001-2250
55
50
40
90
2251-2500
60
55
45
100
Table 7. Low Confidence Areas
Vertical Accuracy
Class
Recommended Project
Min NPD (pts/m
2
) (Max NPS (m))
Recommended Low Confidence
Min NGPD (pts/m
2
) (Max NGPS (m))
Search Radius and Cell Size
for Computing NGPD (m)
Low Confidence Polygons
Min Area(acres (m
2
))
1-cm
≥20 (≤0.22)
≥5 (≤0.45)
0.67
0.5 (2,000)
2.5-cm
16 (0.25)
4 (0.50)
0.75
1 (4,000)
5-cm
8 (0.35)
2 (0.71)
1.06
2 (8,000)
10-cm
2 (0.71)
0.5 (1.41)
2.12
5 (20,000)
15-cm
1 (1.0)
0.25 (2.0)
3.00
5 (20,000)
20-cm
0.5 (1.4)
0.125 (2.8)
4.24
5 (20,000)
33.3-cm
0.25 (2.0)
0.0625 (4.0)
6.0
10 (40,000)
66.7-cm
0.1 (3.2)
0.025 (6.3)
9.5
15 (60,000)
100-cm
0.05 (4.5)
0.0125 (8.9)
13.4
20 (80,000)
333.3-cm
0.01 (10.0)
0.0025 (20.0)
30.0
25 (100,000)
“Due the different
natures of projects,
users of the
standard need
to be aware that
the number of
checkpoints given in
Table 6 is provided
as guideline and
should not be
understood as a
rigid requirement.”
“Such divergence makes it harder for
users during the transition period to
relate the old concepts of map scale
and contour intervals to the new
concepts of the new standard.”
**Dr. Abdullah is Senior Geospatial Scientist and Associate at
Woolpert, Inc. He is the 2010 recipient of the ASPRS Photogrammet-
ric (Fairchild) Award.
The contents of this column reflect the views of the author,
who is responsible for the facts and accuracy of the data pre-
sented herein. The contents do not necessarily reflect the offi-
cial views or policies of the American Society for Photogram-
metry and Remote Sensing and/or Woolpert, Inc.
