TERM NOTE

$10,000,000                                              Los Angeles, California
                                                         As of November 17, 1997
                                                     
         FOR VALUE  RECEIVED,  the  undersigned  promises to pay to the order of
SANWA BUSINESS CREDIT CORPORATION, a Delaware corporation (hereinafter "Lender")
at its  offices  located at 550 North  Brand  Boulevard,  Suite  950,  Glendale,
California  91203, or such other place as Lender may from time to time designate
in writing,  in lawful money of the United States of America,  the principal sum
of Ten Million Dollars ($10,000,000),  plus interest from the date hereof on the
unpaid principal balance, as set forth herein.

         PRINCIPAL. The principal sum hereof shall be payable as follows:

         A. Fifty-nine (59) monthly installments of $119,048 each, commencing on
December  1, 1997 and  continuing  on the first  day of each  consecutive  month
thereafter through and including November 1, 2002; and

         B. The entire unpaid principal  balance,  together with all accrued and
unpaid  interest  thereon and any other amounts due hereunder,  shall be due and
payable on November 16, 2002.

         INTEREST.  Interest  shall be  computed  at the rates and in the manner
provided in the Agreement  (as defined  below) and shall be payable on the first
day of each and every month (commencing December 1, 1997).

         ADDITIONAL PROVISIONS. At the option of Lender, either unpaid principal
or  interest  or both may be  charged to the  undersigned's  loan  account  with
Lender.

         The makers,  endorsers  and  guarantors  of this Term Note hereby waive
presentment for payment, demand, notice of non-payment and dishonor, protest and
notice of protest;  WAIVE TRIAL BY JURY in any action and/or proceeding  arising
on,  out of or under or by reason of this Term Note;  consent  to any  renewals,
extensions and partial  payments of this Term Note or any indebtedness for which
it is given,  and consent that no such renewals  extensions or partial  payments
shall discharge any party hereto from liability hereon in whole or in part. If a
petition under any provision of the U.S. Bankruptcy Code or any other insolvency
statute  for any relief  thereunder  shall be filed  after the date hereof by or
against any maker,  endorser or  guarantor  hereof,  then this Term Note and all
other existing  obligations  of every kind of each maker,  endorser or guarantor
hereof to the holder hereof shall become immediately due and payable.

         It is  expressly  agreed  that if  default  be made in  payment  of any
principal or




interest  installment,  as  above  provided,  or in the  payment  of  any  other
indebtedness  owing to the holder of this Term Note,  the then unpaid  principal
balance due and owing on this Term Note, together with interest accrued thereon,
shall  forthwith  become due and  payable  at the  option of the holder  hereof,
without  presentment,  demand,  protest or notice of protest of any kind, all of
which are hereby expressly waived.

         This  Term  Note  is  secured  by (a)  the  Collateral  pledged  by the
undersigned pursuant to that certain Loan and Security Agreement dated as of the
date  hereof  (the  "Agreement")  between the  undersigned  and Lender,  (b) the
collateral  pledged  by  the  undersigned  pursuant  to  that  certain  Security
Agreement  (Intellectual  Property)  dated as of the  date  hereof  between  the
undersigned and Lender,  and (c) any other collateral  heretofore or at any time
hereafter  pledged by the undersigned to Lender.  The Agreement and the Security
Agreement (Intellectual Property) are hereby incorporated herein in full by this
reference. Capitalized terms used but not defined herein shall have the meanings
given them in the  Agreement.  Any Default under and as defined in the Agreement
shall  constitute a default  hereunder.  If it shall become  necessary to employ
counsel to collect  this  obligation,  or to protect or  foreclose  the security
therefor,  the  undersigned  also agrees to pay reasonable  attorneys'  fees and
costs for the  services of such  counsel,  whether or not suit is brought.  This
Term Note may be prepaid subject to the terms and conditions of the Agreement.

         Lender  shall not be deemed to have waived any of its rights  hereunder
or under any other  agreement,  instrument  or paper  signed by the maker unless
such waiver is in writing and signed by Lender. No delay or omission on the part
of Lender in exercising  any right shall  operate as a waiver  thereof or of any
other right. A waiver upon any one occasion shall not be construed as a bar or a
waiver of any right or remedy as to any future occasion nor shall it establish a
custom or course of dealing.

         This Term Note may not be  changed,  modified,  amended  or  terminated
orally.  The validity of this Term Note, its  construction,  interpretation  and
enforcement,  and the rights of the parties  hereunder shall be determined under
the laws of the State of California.

                      [THIS SPACE INTENTIONALLY LEFT BLANK]


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         Notwithstanding  anything herein to the contrary, in the event that the
Agreement is terminated by the undersigned or by Lender,  then the entire unpaid
principal  balance  of this Term  Note,  together  with all  accrued  and unpaid
interest,  shall become immediately due and payable in full without presentment,
notice or demand of any kind.

                                              NORTHERN GEOPHYSICAL OF AMERICA,
                                                INC.


                                              By:  /s/ Ronald L. Koons
                                                   -------------------
                                              Name:  Ronald L. Koons
                                              Title: Vice President


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