  A global analysis of proton electric form factor experimental data from
Rosenbluth separation and low squared four-momentum transfer experiments is
discussed for the evaluation of the spatial moments of the proton charge
density based on the recently published integral method~\cite{Hob20}. Specific
attention is paid to the evaluation of the systematic errors of the method,
particularly the sensitivity to the choice of the mathematical expression of
the form factor fitting function. Within this comprehensive analysis of proton
electric form factor data, the moments of the proton charge density are
determined for integer order moments, particularly: $\langle r^2
\rangle$=0.682(02)$_{Sta.}$(11)$_{Sys.}$~fm$^2$, $\langle r^3
\rangle$=0.797(10)$_{Sta.}$(58)$_{Sys.}$~fm$^3$, and $\langle r^4
\rangle$=1.02(05)$_{Sta.}$(31)$_{Sys.}$~fm$^4$.
