From the Operations Manual: Procedure for election of candidates by the GRSS members

The Nominations Committee shall submit to the Administrative Committee at least one name of a member of the Society for each vacancy to occur in the Administrative Committee for terms expiring December 31. In addition, the Chair of the Nominations Committee shall ensure that a Call for Nominations is published in the March issue of the GRSS Newsletter. A nominating petition carrying a minimum of 2% of the names of eligible Society members, excluding students, shall automatically place that nominee on the slate. Such nominations must be made at least 28 days before the date of any said election, or April 30, whichever is earlier. Prior to submission of a nomination petition, the petitioner shall have determined that the nominee named in the petition is willing to serve, if elected; evidence of such willingness to serve shall be submitted with the petition.

Petition signatures can be submitted electronically through the Society website, or by signing and mailing a paper petition. The name of each member signing the paper petition shall be clearly printed or typed. For identification purposes of signatures on paper petitions, membership numbers or addresses as listed in the official IEEE membership records shall be included. Only signatures submitted electronically through the Society website or original signatures on paper petitions shall be accepted.

After submission of the slate of candidates by the nominations committee to the IEEE, the election is conducted by IEEE in electronic format and in form paper ballot. Three candidates receiving the greatest number of votes shall be elected.

More information is available here