  The uncertainty of measurement of solar diameter is depending on the
observational time scale. Full-disc images of SDO/HMI and the images from
ground observations in Huairou Solar Observing Station have been analyzed to
get the values of solar diameter. The satellite observations reach a very high
precision, but the absolute image scale still need to be calibrated. The solar
oblateness is a more challenging measurement than the diameter, since the
signal amplitude is a few milli-arcseconds. It is a relative measurement, then
not affected by the pixel scale calibration required by the diameter
measurement. But the results are strongly dependent on the state of instrument
such as focus plane deformation and on the calculation process.
