

                                                                  Exhibit 10.70

                           TRIMBLE NAVIGATION LIMITED

                                FOURTH AMENDMENT


     THIS FOURTH AMENDMENT (this  "Amendment") is entered into as of October 20,
1999 by and among TRIMBLE NAVIGATION  LIMITED,  a California  corporation having
its chief executive office at 645 North Mary Avenue, Sunnyvale, California 94086
(the  "Borrower")  and FLEET  NATIONAL  BANK,  a  national  banking  association
organized  under  the laws of the  United  States  and  having  an office at One
Federal  Street,  Boston,  Massachusetts  02110,  as the  Agent and as a Lender,
BANKBOSTON,  N.A., a national banking  association,  organized under the laws of
the United States and having an office at One Hundred  Federal  Street,  Boston,
Massachusetts  02110,  as the  Syndication  Agent  and as a Lender,  SANWA  BANK
CALIFORNIA,  a  banking  corporation  organized  under  the laws of the State of
California and having an office at 220 Almaden Boulevard,  2nd Floor,  San Jose,
California  95113,  as a Lender,  and ABN AMRO BANK N.V., a Netherlands  banking
corporation  having  an  office  at  101  California  Street,  Suite  4550,  San
Francisco,  California 94115, as a Lender,  under the Loan Agreement (as defined
below), to which reference is made for the definitions of all capitalized terms,
used, but not otherwise defined, herein.

                                 R E C I T A L S

     WHEREAS,  the parties have entered into a Loan Agreement dated as of August
27, 1997 among the Borrower,  the Agent, the Syndication  Agent, and the lenders
from time to time  party  thereto  (the  "Lenders"),  as  amended by a Letter of
Amendment dated December 17, 1997, and a Second Letter of Amendment dated August
11, 1998 and a Third Amendment dated as of February 16, 1999 (the  "Agreement"),
pursuant to which the Lenders issued a Revolving  Credit Loan  Commitment to the
Borrower in the maximum principal amount of $50,000,000;

     WHEREAS,  pursuant to a certain  Waiver Letter dated October 27, 1998 and a
certain  Supplement  to  Loan  Agreement  and  Additional  Waiver  Letter  dated
December 9, 1998,  the Borrower was granted a limited waiver with respect to the
Borrower's  compliance with certain covenants contained in the Agreement for the
Borrower's   fiscal  quarters  ended  October  2,  1998  and  January  1,  1999,
conditional  upon  the  satisfaction  of  certain  specified  waiver  conditions
contained  therein on or prior to February 16, 1999,  which was satisfied by the
above-referenced Third Amendment;

     WHEREAS,  the Borrower has  requested  the Agent and the Lenders to further
amend the Agreement as  hereinafter  set forth and the Agent and the Lenders are
willing to do so;

     NOW THEREFORE,  in  consideration of the mutual benefits to be derived from
the parties' continuing  relationship under the Agreement and for other good and
valuable   consideration,   the  receipt  and   adequacy  of  which  are  hereby
acknowledged,  the Borrower,  the Agent, the Syndication  Agent, and the Lenders
hereby  agree that the  Agreement  is hereby  amended,  effective as of the date
first set forth above (the "Effective Date"), as follows:

     1. Section 1.1 of the Agreement is hereby  further  amended by the addition
of the following new defined term to be added alphabetically thereto:

     "Allowed  Repurchase"  means the repurchase by the Borrower from certain of
Borrower's  stockholders  of up to an aggregate  of  $30,000,000  of  Borrower's
capital stock with the proceeds of the Borrower's sale of certain assets.

     2. Section  5.1.10 of the  Agreement  is hereby  amended in its entirety to
read as follows:

     Section 5.1.10. Maximum Ratio of Total Funded Debt to Total Capitalization.
Commencing September 30, 1999, maintain a ratio of (i) Total Funded Debt to (ii)
Total Capitalization of less than .7:1.00.

     3. Section  5.1.11 of the  Agreement  is hereby  amended in its entirety to
read as follows:



     Section 5.1.11.  Minimum  Consolidated  Tangible Net Worth.  (i) Maintain a
Consolidated  Tangible  Net  Worth in an  amount  not less  than the  Borrower's


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Consolidated  Tangible Net Worth as of the end of the  Borrower's  September 30,
1999 fiscal quarter minus the sum of $5,000,000 and the lesser of (a) the amount
of the Allowed  Repurchase and (b) $30,000,000,  and (ii) comply with Section 8K
of the Note  Purchase  Agreement  dated as of June 13, 1994 among the  Borrower,
John Hancock  Mutual Life and John Hancock  Life  Insurance,  as the same may be
amended,  amended and restated,  supplemented or otherwise modified from time to
time.

     4. Section  5.1.12 of the  Agreement  is hereby  amended in its entirety to
read as follows:

     Section 5.1.12.  Minimum Cash Balances.  Maintain at all times on and after
the Effective Date unrestricted cash balances and Cash Equivalent Investments in
an amount  equal to or  greater  than  $50,000,000  of which  unrestricted  cash
balances and Cash Equivalent Investments (to the extent and of types issued by a
Lender) in an amount equal to or greater than the aggregate  outstanding  amount
of the Obligations  (including without limitation the Revolving Credit Loan, the
aggregate  outstanding  amount of any Letters of Credit and any Unpaid Drawings)
must be kept in one or more accounts maintained by the Borrower with one or more
of the Lenders.

     5. Section 5.2.8 of the Agreement is hereby amended in its entirety to read
as follows:

     Section  5.2.8.  Overall  Aggregate  Cap.  Notwithstanding  the  terms  and
conditions  of  Sections  5.2.4,  5.2.6,   5.2.7.3,   5.2.7.4  and  5.2.10,  the
Consolidated Tangible Net Worth measurements of permitted transactions contained
therein are subject to an aggregate  Consolidated  Tangible Net Worth limitation
of  thirty  percent  (30%)  of  Consolidated  Tangible  Net  Worth  for all such
transactions  permitted  by any  of  said  Sections  excluding,  to  the  extent
otherwise includable therein, the Allowed Repurchase.

     6. Exhibit  3.1.1.10 to the Agreement  (Form of Compliance  Certificate) is
hereby  deleted and a new  Exhibit  3.1.1.10  in the form  attached  hereto as "
Exhibit 3.1.1.10 " is substituted in its stead.

     7. This  Amendment  shall take effect as of the Effective Date upon receipt
by the Agent of this Amendment duly executed by the parties hereto.

     8. The Borrower hereby represents and warrants to the Agent and the Lenders
that no Default or Event of Default exists
under the Agreement.

     9. This  Amendment  is  executed as an  instrument  under seal and shall be
governed by and construed in  accordance  with the laws of The  Commonwealth  of
Massachusetts  without  regard to its  conflicts of law rules.  All parts of the
Agreement not affected by this Amendment are hereby ratified and affirmed in all
respects,  provided that if any provision of the Agreement  shall conflict or be
inconsistent  with this  Amendment,  the terms of this Amendment shall supersede
and prevail.  Upon and after the date of this  Amendment  all  references to the
Agreement in that document, or in any related document, shall mean the Agreement
as amended by this  Amendment.  Except as expressly  provided in this Amendment,
the execution and delivery of this Amendment does not and will not amend, modify
or  supplement  any  provision of, or constitute a consent to or a waiver of any
noncompliance with the provisions of the Agreement,  and, except as specifically
provided in this Amendment, the Agreement shall remain in full force and effect.
This Amendment may be executed in one or more  counterparts with the same effect
as if the signatures hereto and thereto were upon the same instrument.


             [THE BALANCE OF THIS PAGE IS INTENTIONALLY LEFT BLANK]


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     IN WITNESS WHEREOF, each of the Borrower, the Agent, the Syndication Agent,
and the Lenders in accordance with Section 9.5 of the Agreement, has caused this
Amendment  to be executed  and  delivered by their  respective  duly  authorized
officers as an instrument under seal as of the Effective Date.

                                   BORROWER:

                                   TRIMBLE NAVIGATION LIMITED


                                   By: /s/ John E. Huey________________________
                                          John E. Huey
                                          Treasurer


                                   AGENT:

                                   FLEET NATIONAL BANK


                                   By: /s/ Mathew M. Glauninger________________
                                          Mathew M. Glauninger
                                          Senior Vice President


                                   SYNDICATION AGENT:

                                   BANKBOSTON, N.A.


                                   By:/s/ Anthony B. Kwee______________________
                                          Anthony B. Kwee
                                          Vice President


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                                   LENDERS:

                                   FLEET NATIONAL BANK


                                   By: /s/ Mathew M. Glauninger
                                          Mathew M. Glauninger
                                          Senior Vice President


                                   BANKBOSTON, N.A.

                                   By: /s/ Anthony B. Kwee_____________________
                                          Anthony B. Kwee
                                          Vice President


                                   SANWA BANK CALIFORNIA

                                   By: /s/ Jillian Mathur______________________
                                          Jillian Mathur
                                          Vice President



                                   ABN AMRO BANK N.V.

                                   By:_________________________________________
                                          _____________________________________
                                                        Print Name
                                   Title:______________________________________

                                   By:_________________________________________
                                          _____________________________________
                                                        Print Name
                                   Title:______________________________________


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<PAGE>



                EXHIBIT 3.1.1.10 - FORM OF COMPLIANCE CERTIFICATE


Fleet National Bank
One Federal Street
Boston, MA 02110

  Attention:________Mathew M. Glauninger, Senior Vice President
                    High Technology Group,   MA OF DO7A

  Re: Compliance Certificate Required by Sections 3.1.1.10 or 5.3.4 of the Loan
      Agreement dated as of August 27, 1997 by and among you as Agent,
      BankBoston, N.A., as the Syndication Agent, the undersigned and the
      Lenders from time to time party thereto, as amended from time to time
      (the "Loan Agreement")

Gentlemen:

     This certificate is submitted by the undersigned (the "Borrower")  pursuant
to  Sections 3.1.1.10  or 5.3.4 of the Loan  Agreement.  Capitalized  terms used
herein have the same meaning as in the Loan Agreement.

     The  Borrower  hereby  certifies  to the  Agent  and the  Lenders  that the
following information is true, accurate and complete as of the Borrower's fiscal
quarter ending ____________, ________ (the "Quarter").

Section 5.1.10.  Maximum Ratio of Total Funded Debt to Total
                    Capitalization  (Calculated as at end of the Quarter)

(a)    Obligations (all Indebtedness under
       Financing Documents)................................$___________________

(b)    Subordinated Debt...................................$___________________

(c)    Capitalized Lease Obligations.......................$___________________

(d)    Total Funded Debt [Sum of Lines (a) - (c)]..........$___________________

(e)    Consolidated Net Worth..............................$___________________

(f)    Total Capitalization [Sum of Line (d) + Line (e)]...$___________________

(g)    Actual Ratio: [Line (d) divided by Line (f)]........            :1.0

(h)    Maximum Ratio Permitted by Agreement................            :1.0


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<PAGE>

Section 5.1.11. Minimum Consolidated Tangible Net Worth
                  (Calculated as at end of the Quarter)

 (a)    Total assets of Borrower and Subsidiaries...............$______________

 (b)    Consolidated Total Liabilities..........................($_____________)

 (c)    Consolidated Net Worth
        [Line (a) minus Line (b)]...............................$______________

 (d)    Excluded items (if any)* ...............................($_____________)

 (e)    Consolidated Tangible Net Worth.........................$______________

 (f)    Minimum Permitted by Agreement:

        (i)  Consolidated Tangible Net Worth
        as at September 30, 1999 quarter end minus sum of $5,000,000
        and lesser of Allowed Repurchase and
        $30,000,000, i.e., $________............................$______________

        (ii) Minimum "Consolidated Net Worth"
        Required Under Section 8K of Note Purchase Agreement
        dated 6/13/94 ("NPA")...................................$______________

Section 5.1.12.  Minimum Cash Balances..
                    (Calculated on any date after September 30, 1999)

 (a)   Obligations (under Financing Documents)..................$______________

        (i)    Revolving Loans   $_____________________
        (ii)   Letters of Credit $_____________________

(b) Total Cash Balances and Cash Equivalent Investments.........$______________

(c) Minimum Required by Agreement.................................$50,000,000.

(d) Total Cash Balances and qualified Cash Equivalent Investments
   in accounts with Lenders.......................................$____________

(e) Minimum Required is amount of (a)











--------
* Excluded items are (a)book value of intangible assets,  including  goodwill,
unamortized debt discount and expense,  patents,  trade and  service   marks
and  names,   copyrights,   franchises,   etc.  of   $_______________________;
and  (b)  other   (describe)  of $__________________________.



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<PAGE>


Section 5.1.13.  Minimum Quick Ratio.
                    (Calculated as at end of the Quarter)

(a)    Cash.....................................................$______________

(b)    Cash Equivalent Investments..............................$______________

(c)    Net outstanding amount of
       accounts receivable......................................$______________

(d)    Sum of Lines (a), (b) and (c)............................$______________

(e)    Current Liabilities......................................$______________

(f)    Less Current Liabilities consisting of Revolving Credit Loans..($_______)

(g)    Line (e) minus Line (f)........................................$________

(h)    Quick Ratio [Line (d) divided by Line(g).......................   :1.0

(g)    Minimum Quick Ratio Permitted by Agreement.....................   :1.0

Section 5.2.9.  Minimum Operating and Net Income.

Calculated as at end of the Quarter:

(a)    Net income (loss) (GAAP) as at end of the Quarter............$__________

(b)    Less extraordinary or other non-recurring gains
       as at end of the Quarter.....................................($_________)

(c)    Less gains from sale or other non-ordinary course
       disposition of assets as at end of the Quarter...............($_________)

(d)    Net Income as at end of the Quarter
       [Line (a) minus sum of Lines (b) and (c)]....................$__________

Calculated as at End of Immediately Preceding Quarter:

(e)    Net income (loss) (GAAP) as at end of the fiscal quarter
       immediately preceding the Quarter............................$__________

(f)    Less extraordinary or other non-recurring gains as at end of
       the fiscal quarter immediately preceding the Quarter.........($_________)


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(g)    Less gains from sale or other non-ordinary course
       disposition of assets as at end of the fiscal quarter
       immediately preceding the Quarter.............................($________)

(h)    Net Income as at end of the fiscal quarter immediately
       preceding the Quarter
       [Line (e) minus sum of Lines (f) and (g)].....................$_________

Calculated as at End of Second Immediately Preceding Quarter:

(i)    Net income (loss) (GAAP) as at end of the fiscal quarter
       immediately preceding the Quarter.............................$_________

(j)    Less extraordinary or other non-recurring gains as at end of
       the fiscal quarter immediately preceding the Quarter..........($________)

(k)    Less gains from sale or other non-ordinary course
       disposition of assets as at end of the fiscal quarter
       immediately preceding the Quarter.............................($________)

(l)    Net Income as at end of the fiscal quarter immediately
       preceding the Quarter
       [Line (i) minus sum of Lines (l) and (k)].....................$_________

Calculated as at End of Third Immediately Preceding Quarter:

(m)    Net income (loss) (GAAP) as at end of the fiscal quarter
       immediately preceding the Quarter.............................$_________

(n)    Less extraordinary or other non-recurring gains as at end of
       the fiscal quarter immediately preceding the Quarter..........($________)

(o)    Less gains from sale or other non-ordinary course
       disposition of assets as at end of the fiscal quarter
       immediately preceding the Quarter.............................($________)

(p)    Net Income as at end of the fiscal quarter
       immediately preceding the Quarter
       [Line (m) minus sum of Lines (n) and (o)].....................$_________

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<PAGE>



(q)    Net Income

       The Quarter [line (d)], plus Excluded items (if any)** of $___....$_____
       Immediately Preceding Quarter [line (e)]
         plus excluded items (if any)** of $__________.................$_______
       Second Immediately Preceding Quarter [line (i)]
         plus Excluded items (if any)** of $__________.................$_______
       Third Immediately Preceding Quarter [line (m)]
         plus excluded items (if any)** of $__________.................$_______

(r)    Operating Income

       The Quarter plus Excluded items (if any) **
         of $_________________________.................................$_______
       Immediately Preceding Quarter plus excluded items (if any)**
         of $_________________________.................................$_______
       Second Immediately Preceding Quarter plus
         Excluded items (if any) ) ** of $___________________..........$_______
       Third Immediately Preceding Quarter
         plus excluded items (if any)** of $_________________..........$_______

(s)    Minimum Operating Income and Net Income
         Required under the Agreement:

     (i) during the period  beginning with the Borrower's  fiscal quarter ending
         March, 1999  and  ending on the fiscal  quarter ending  December, 1999,
         have a negative  Operating Income or a negative Net Income for any two
         fiscal quarters, and

     (ii) as of the end of each fiscal quarter of the Borrower  commencing  with
          the Borrower's fiscal quarter ending in March, 2000, have a negative
          Operating Income, or a negative Net Income for the rolling four
          quarter fiscal period consisting of such fiscal quarter and the three
          immediately preceding fiscal quarters.











-------------
**  Excluded  items are any  amount  taken as a one-time  charge  against
earnings  attributable  to (a)  settlement  of class  action litigation;
(b)  closing  of  commercial  marine  division;  and  (c)  reduction  in
employees  resulting  from  switch  to  contract manufacturing, (a) - (c) not
to exceed $2,000,000 in the aggregate.


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<PAGE>

     The Borrower further certifies to the Lenders that as of the date hereof no
Event of Default or Default has occurred without having been waived in writing.

                                            TRIMBLE NAVIGATION LIMITED


                                            By:
                                               Name:  [                        ]
                                               Title:    [                     ]




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