INVERSION OF SYNTHETIC APERTUR,E R,ADAR (SAR) - MSpace ...

distinct points can be cliscelnerl in Figur.e 6.17 except for.subtle changes in
brightness. Lorv DN-r'alues of fold stluctules alcl lorv tonal contrast of folcl
structuÌes ivith acljacent fielcls in the iuage rnay be responsible for this pool
Iesult.
Correlatioli using tlìe Radon ttansform rvas testecl with the sarne clata
as usecl above. The corlelation plocess, a silnple shiftiug plocesses iu
z-clirnensiol as pteviously explained, was pelfolrnecl after screening in the
Raclon space. The scleening plocess il the Raclon space detects a celtain
level of arnplitucle of the Raclon transformecl values and replaces thern lvith
a specifiecl values. Most bright lines in the test SAR irnage (Figure 6.15) are
sholelines parallel or subpai'allel to azimuth. Thus, one carr expect that the
high amplitucles of the Radon transform are colrtributions from these br.ight
shoreliues.
Fold structures rvhich are rnain targets to be located are explessecl by
low ÐN-values. Fol the reason, the high arnplitucle of the Radon transfolm
signatule are not useful for this specific purpose. The scr.eening pr.ocess
adoptecl is as follows:
1) fincl the rnaxirnurn arnplitude of the Raclol transform ancl multiply it
by a rveighting factor' (0.8 in this test) to make a ceiliug value,
2) keep the amplitucle if it is less than the ceiling value estirnated by 1),
ot
3) replace tlie amplitude by the ceililg value if the arnplitude is higher
than this level.
147