[lemma=in] | [□] □
[lemma=in] | [□=□] □
[lemma=in] | [!□] □
In effect , each system can provide tie points to help understand and remove the effect of attitude errors in the other system . Perhaps the major constraint on any stereo-optical approach is the existence of clouds in the Earth 's atmosphere . Such studies , together with observational results , suggest that SAR can observe changes in the ocean wave spectrum at the Bragg wavelength as small as a few percent .