X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 10 Dec 2007 00:19:21 -0500 Message-ID: X-Original-Return-Path: Received: from elasmtp-junco.atl.sa.earthlink.net ([209.86.89.63] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTP id 2573928 for lml@lancaironline.net; Sun, 09 Dec 2007 22:34:30 -0500 Received-SPF: neutral receiver=logan.com; client-ip=209.86.89.63; envelope-from=mnewman@dragonnorth.com Received: from [70.91.142.49] (helo=PCmike2) by elasmtp-junco.atl.sa.earthlink.net with asmtp (Exim 4.34) id 1J1ZOw-0007NM-MY; Sun, 09 Dec 2007 22:33:51 -0500 From: "Michael Newman" X-Original-To: "'Taylor, David'" , X-Original-Cc: References: Subject: RE: [LML] Computing TAS from GPS tracks X-Original-Date: Sun, 9 Dec 2007 22:34:30 -0500 Organization: Dragonnorth Group X-Original-Message-ID: <007301c83add$936803b0$0401a8c0@sentira.net> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0074_01C83AB3.AA91FBB0" X-Mailer: Microsoft Office Outlook 11 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 Thread-Index: Acg6ra9GRENcqiF9RMObBCWDq1hu+AALpDzg In-Reply-To: X-ELNK-Trace: 4981850a937e3365551c28c27865cf0a239a348a220c2609c5f945985c2366af30db20acf7d4edfda8438e0f32a48e08350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 70.91.142.49 This is a multi-part message in MIME format. ------=_NextPart_000_0074_01C83AB3.AA91FBB0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit The CSG on line calculator has a serious error. If your compass has any error the angles will not be exactly 90 degrees and the compass error will contribute to an error in the TAS and wind estimation. The method I presented is more complex. Because you feed it the GPS tracks it does not care about your actual headings. It actually computes the compass heading allowing you to observe the compass error. _____ From: Taylor, David [mailto:dtaylor@crescentpark.com] Sent: Sunday, December 09, 2007 4:47 PM To: lml@lancaironline.net Subject: RE: [LML] Computing TAS from GPS tracks Mike - you have the right idea. This website also does the calc: http://www.csgnetwork.com/tasgpscalc.html Or you can just find the wind direction and fly into the wind and then turn 180 and fly out of the wind and just average your groundspeeds. This is also TAS. But it's tricky finding the wind direction. You need to line up your heading and your track to find it. My GRT in my Legacy was computing a TAS that is 5 knots too high for instance. GRT lets you calibrate this so now its more accurate! Dave T. Legacy RG From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Michael Newman Sent: Fri, 12-07-2007 19:14 To: lml@lancaironline.net Subject: [LML] Computing TAS from GPS tracks I've been doing some homework on how to calibrate airspeed indications and get the TAS of a plane. Given 3 GPS tracks taken at the same airspeed you can compute a complete solution for the heading on each track and the TAS. Folks might be interested in my spreadsheet which contains real data from my plane at low altitude. I will gather some more data over time. You can find my spreadsheet via my Soaring and Flying page at: http://www.dragonnorth.com/soaring.html scroll down a bit there is discussion a link to a reference document and a link to the spreadsheet itself. My true airspeed as computed from my airspeed indicator is about 14 knots faster that the measured result. _____ Michael Newman Dragonnorth Group 319 Dean Rd. Brookline, MA 02445 Cell: 617 821-4608 Home: 617 566-7975 Fax: 617 566-7975 www.dragonnorth.com mnewman@dragonnorth.com ------=_NextPart_000_0074_01C83AB3.AA91FBB0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
The CSG on line calculator has a serious error. If your = compass has=20 any error the angles will not be exactly 90 degrees and the compass = error will=20 contribute to an error in the TAS and wind estimation. =
 
The method I presented is more complex. Because you feed it the = GPS=20 tracks it does not care about your actual headings. It actually computes = the=20 compass heading allowing you to observe the compass=20 error.

From: Taylor, David=20 [mailto:dtaylor@crescentpark.com]
Sent: Sunday, December 09, = 2007=20 4:47 PM
To: lml@lancaironline.net
Subject: RE: [LML] = Computing TAS from GPS tracks

Mike=20 – you have the right idea.  This website also does the = calc:  http://www.csgnetwork.= com/tasgpscalc.html

 

Or=20 you can just find the wind direction and fly into the wind and then turn = 180 and=20 fly out of the wind and just average your groundspeeds.  This is = also=20 TAS.  But it’s tricky finding the wind direction.  You = need to line up=20 your heading and your track to find it.

 

My=20 GRT in my Legacy was computing a TAS that is 5 knots too high for=20 instance.  GRT lets you calibrate this so now its more=20 accurate!

 

Dave=20 T.

Legacy=20 RG

 

From: Lancair = Mailing=20 List [mailto:lml@lancaironline.net] On Behalf Of Michael=20 Newman
Sent: Fri, 12-07-2007 19:14
To:=20 lml@lancaironline.net
Subject: [LML] Computing TAS from GPS=20 tracks

 

I've been = doing some=20 homework on how to calibrate airspeed indications and get the TAS of a = plane.=20 Given 3 GPS tracks taken at the same airspeed you can compute a complete = solution for the heading on each track and the = TAS.

 

Folks might = be=20 interested in my spreadsheet which contains real data from my plane = at low=20 altitude. I will gather some more data over time.

 

You can = find my=20 spreadsheet via my Soaring and Flying page at: http://www.dragonnorth.c= om/soaring.html scroll=20 down a bit there is discussion a link to a reference document and a link = to the=20 spreadsheet itself.

 

My true = airspeed as=20 computed from my airspeed indicator is about 14 knots faster that the = measured=20 result.

 

Michael=20 Newman

Dragonnorth Group

319 Dean=20 Rd.
Brookline, MA 02445

Cell: 617 821-4608
Home: 617 566-7975
Fax: 617 = 566-7975

www.dragonnorth.com

mnewman@dragonnorth.com<= /o:p>

 

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