1. Sustaining Members are individuals, organizations, institutions or agencies who manufacture or distribute instruments, equipment or supplies, or who operate or provides services in the fields of photogrammetry, remote sensing and/or GIS, or who are engaged in research and/or education, and who contribute to the financial support of the Society.
2. Sustaining Members shall pay an annual fee according to the invoice from the Treasurer at the beginning of each calendar year. There shall be 5 categories as follows:

      Category         Num.Specialists               Annual Subscription
    -------------------------------------------------------------------------
         A         more than 750 employees            3450  Swiss Francs
         B             100 - 750 employees            1725  Swiss Francs 
         C              25 - 100 employees             920  Swiss Francs 
         D               1 -  25 employees             460  Swiss Francs 
         E          Educational Institutes             250  Swiss Francs 
   

   
   Sustaining Members are encouraged to increase their contribution but such additional contributions will not change the category of membership. A Sustaining Member who is more than two years in arrears shall be dropped from the rolls.
3. Applicants for status as Sustaining Members shall file with the Secretary General a written statement (less than 1000 words) describing their photogrammetric and/or remote sensing activities. Applicants shall commit to membership for a minimum of four years. Application shall be approved unless two or more members of Council submit objections in writing. Any such objections shall be forwarded to the applicant who shall have right of rebuttal.
4. The Secretary General will maintain a list of current Sustaining Members and the description of their activities. This information will be printed in appropriate Society publications. A Sustaining Member may revise the description of activities whenever it may be necessary.
5. At an appropriate time near the end of each Congress, the current Congress Director will schedule a meeting of the Sustaining Members to review the exhibit and other congress activities. The current Congress Director or his representative shall preside at this meeting. The incoming Congress Director will be an observer.
6. Approximately two years before each Congress, the Secretary General will schedule and invite to a meeting of the Sustaining Members at an appropriate time and place. A preliminary agenda for the meeting will be attached to the invitation. A member of the ISPRS Council, preferably the Congress Director, shall preside at this meeting. Not less than 8 weeks before this meeting the Congress Director will distribute to the Sustaining Members a written description of the plans for the next Congress.
7. Not less than 4 weeks before the inter-Congress scheduled Meeting, Sustaining Members shall inform the Secretary General in writing of any items they wish included on the agenda and the name of their delegate. Voting by proxy shall be allowed provided it is designated in writing to the Secretary General in advance of the meeting. For the Congress meeting, designation of delegates and proxies may be made during the Congress.
8. At any meeting of the Sustaining Members, the number of votes will be determined by membership category as follows:

      Category     A    B    C    D    E
      Votes        8    4    2    1    1
   

   In matters related to the Congress, deliberations of Sustaining Members shall be advisory only; the Congress Director has final authority for all Congress plans.
9. Sustaining Members will be provided with a suitable Certificate and shall have the right to indicate in their business and professional publications that they are Sustaining Members of ISPRS.
10. Amendments to these Terms of Reference which do not result in conflict with articles in the Statutes and Bylaws may be adopted by majority vote at any meeting of the Sustaining Members.
11. The Council recommends that the Congress Director provide exhibition space at the Congress to Sustaining Members at a discount rate.

Approved by Sustaining Members Meeting at XVI ISPRS Congress in Kyoto, July 1988.
Categories amended by General Assembly mail ballot, February, 1993.
Amendments approved at Sustaining Members Meeting at XVIII ISPRS Congress in Vienna, July 1996.
Amendments approved by the General Assembly at XX ISPRS Congress in Istanbul, July 2004.