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Contact Info
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GisBox SRL

BUCHAREST - ROMANIA
Email: info@gisbox.ro
Email: office@gisbox.ro

Phone: +4031 424 75 09
 AQL's

Our experience commits us to quality, quality implies accuracy!

     AQL's

     Aerial Triangulation

     Genneraly, RMSxyz for the Ground Control Points determination is estimated at maximum 6 cm. With today technology, the Ground Control Points precisioin is even better of 1 cm. Considering that the measurement of Ground Control is performed with an accuracy of ½ pixel size, the overall RMSExyz for AT is expected to be between ½ and 1 pixel.
     RMS of an orthorectified image depending only on the Ground Control Points & Aerial Triangulation - RMSxy1:

Ground Sample Distance RMSxy1 of the orthophoto depending on
the Ground Control Points + AT
0.10 m 0.11 m or BETTER
0.125 m 0.13 m or BETTER
0.15 m 0.18 m or BETTER
0.20 m 0.23 m or BETTER
0.25 m 0.28 m or BETTER
0.30 m 0.34 m or BETTER
0.40 m 0.45 m or BETTER
0.50 m 0.56 m or BETTER

     DTM

     Depending of the GSD of orthophotomaps (for relativly flat areas) the final RMSz of DTM will be:

Ground Sample Distance RMSz
0.10 m 0.13 m or BETTER
0.125 m 0.15 m or BETTER
0.15 m 0.18 m or BETTER
0.20 m 0.30 m or BETTER
0.25 m 0.35 m or BETTER
0.30 m 0.40 m or BETTER
0.40 m 0.50 m or BETTER
0.50 m 0.60 m or BETTER

     Planimetric RMS of an orthorectified image depending on the accuracy of the DTM

     An estimation of the planimetric RMS depending on the accuracy of the DTM is:
          RMSxy=r3/( 3  *f)*RMSz
          with f is Focal length
          RMSz is RMS of the DTM
          r3= r12+r22 
          r1 is the half-length and r2 the half-height, 4r1r2 the useful surface of the photo.
          For the camera Vexel UCD with the focal length of 101.4 mm and dimensions of 67.5x103.5 mm and overlaps of 60x20%, r3 is:
r1 = 0.0675*(1-0.6)/2 = 0.014 m, r2 = 0.1035*(1-0.25)/2 = 0.039 m , r3 = 0.041 m that means :
          RMSxy = 0.234•RMSz
Depending only on RMSz for the DTM, the second RMSxy2 for the orthophoto should be:

Ground Sample Distance RMSz of the DTM RMSxy2 depending on the DTM
0.10 m 0.13 m 0.03 m
0.125 m 0.15 m 0.04 m
0.15 m 0.18 m 0.04 m
0.20 m 0.30 m 0.07 m
0.25 m 0.35 m 0.08 m
0.30 m 0.40 m 0.09 m
0.40 m 0.50 m 0.12 m
0.50 m 0.60 m 0.14 m

     Orthophoto

     The horizontal accuracy of the digital ortho-images is a combination of the accuracy of the Ground Control Points and subsequent Aerial Triangulation and the altimetric accuracy of the DTM.
     Supposing the two errors RMSxy1 and RMSxy2 are not correlated, the final RMSxy for an orthophoto is:

Ground Sample Distance RMSxy1 RMSxy2 RMSxy Orthophoto
0.10 m 0.13 m 0.03 m 0.10 m
0.125 m 0.15 m 0.04 m 0.12 m
0.15 m 0.18 m 0.04 m 0.17 m
0.20 m 0.30 m 0.07 m 0.22 m
0.25 m 0.35 m 0.08 m 0.27 m
0.30 m 0.40 m 0.09 m 0.32 m
0.40 m 0.50 m 0.12 m 0.42 m
0.50 m 0.60 m 0.14 m 0.52 m