(4)
Method
Number
of
ground
control
points
Xrms
Yrms
Trmas
Affine
28
0.2626
0.2990
0.3980
2nd order affine
28
0.2309
0.2781
0.3615
3rd order affine
28
0.2310
0.2772
0.3608
4th order affine
28
0.2309
0.2771
0.3607
5 th order affine
28
0.2308
0.2763
0.3601
6th order affine
28
0.2309
0.2772
0.3607
Table 3. Total RMS errors by using different method
Y r
Trma *\j X rms + Y r
(5)
where X RMS is the root mean square error of X, Y RMS the root
mean square error of Y, T RMAS the root mean square error, n the
number of ground control points, XR i the residual error of
one ground control point on the direction of X, and YR t the
residual error of one ground control point on the direction of Y.
It is obvious from the Table 4, the RMS errors of geometric
correction gradually reduce along with the increasing of
polynomial order number, and the RMS error is smallest when
the polynomial order number is 5. If the order increases, the
RMS error will increase, too. RMS errors of the second order
polynomial are smaller than 0.5 pixels, which satisfies the
requirement of the remote sensing images.
Where X RMS , Yrms and Trmas are the units of pixel, and
XrmS~
(3)
3.3.2 RMS errors of checking points: 15 checking points
are selected uniformly on the corrected images to inspect the
correcting situation and the errors of checking points are shown
in Table.4.
Point
number
Position of point
after correction
Actual coordinate of
checking point
Position errors of
checking point
RMS of
simple- point
Notes
X(m)
Y(m)
X(m)
Y(m)
AX
AY
2
513037.07828
654965.98000
513037.264
654966.274
-0.186
-0.294
0.348
3
513043.66497
654680.98932
513043.990
654681.072
-0.325
-0.083
0.335
4
513392.58553
655043.75214
513392.375
655043.483
0.211
0.269
0.342
5
513528.14427
654788.86352
513528.105
654788.748
0.039
0.116
0.122
6
513043.89808
654159.42341
513043.674
654159.180
0.224
0.243
0.331
7
512912.76734
654784.41835
512912.791
654784.256
-0.024
0.162
0.164
8
513087.59714
654566.23453
513087.801
654566.552
-0.204
-0.317
0.377
9
513880.31298
654107.97735
513880.067
654107.837
0.246
0.140
0.283
RMS 6 = ±j-RMSf
V n
= ±0.350/w
10
513259.60275
655028.67721
513259.780
655028.585
-0.177
0.092
0.200
11
513101.07165
654059.19855
513101.634
654059.462
-0.562
-0.263
0.621
12
513508.37463
654478.69624
513508.741
654478.865
-0.366
-0.169
0.403
13
513130.33893
653667.74868
513130.263
653667.400
0.076
0.349
0.357
14
513266.91957
654262.85005
513266.556
654262.573
0.364
0.277
0.457
15
513603.45999
653996.68264
513603.349
653996.299
0.111
0.384
0.399
Table 4. Errors of checking points after geometries correction
The total RMS error of control points is 0.35m. The control
point of geometric correction and checking points are rooted in
the digital topographic maps of 1:500 scaled, so that
RMS Toatal —
Real ^Control (6)
"W =±>M4„,- m L mi =±Vo.35 2 -O.l 2 =±0.335«
