Context : The interaction of plasma motions and magnetic fields is an important mechanism , which drives solar activity in all its facets .
For example , photospheric flows are responsible for the advection of magnetic flux , the redistribution of flux during the decay of sunspots , and the built-up of magnetic shear in flaring active regions .

Aims : Systematic studies based on G-band data from the Japanese Hinode mission provide the means to gather statistical properties of horizontal flow fields .
This facilitates comparative studies of solar features , e.g. , G-band bright points , magnetic knots , pores , and sunspots at various stages of evolution and in distinct magnetic environments , thus , enhancing our understanding of the dynamic Sun .

Methods : We adapted Local Correlation Tracking ( LCT ) to measure horizontal flow fields based on G-band images obtained with the Solar Optical Telescope on board Hinode .
In total about 200 time-series with a duration between 1–16 h and a cadence between 15–90 s were analyzed .
Selecting both a high-cadence ( \Delta t = 15 s ) and a long-duration ( \Delta T = 16 h ) time-series enabled us to optimize and validate the LCT input parameters , hence , ensuring a robust , reliable , uniform , and accurate processing of a huge data volume .

Results : The LCT algorithm produces best results for G-band images having a cadence of 60–90 s. If the cadence is lower , the velocity of slowly moving features will not be reliably detected .
If the cadence is higher , the scene on the Sun will have evolved too much to bear any resemblance with the earlier situation .
Consequently , in both instances horizontal proper motions are underestimated .
The most reliable and yet detailed flow maps are produced using a Gaussian kernel with a size of 2560 km \times 2560 km and a full-width-at-half-maximum ( FWHM ) of 1200 km ( corresponding to the size of a typical granule ) as sampling window .

Conclusions : Horizontal flow maps and graphics for visualizing the properties of photospheric flow fields are typical examples for value-added data products , which can be extracted from solar databases .
The results of this study will be made available within the ‘ small projects ’ section of the German Astrophysical Virtual Observatory ( GAVO ) .