Effect of Free Gama Adjustment
Jim Sutherland <[email protected]> Sat, 27 Mar 2004 11:19:24 -0800
| Newsgroups | gmane.comp.gnu.gama.announce |
|---|---|
| Message-ID | <[email protected]> |
This is a multi-part message in MIME format. --===============0095662343== Content-type: multipart/alternative; boundary="----=_NextPart_000_000D_01C413ED.5C3F84A0" This is a multi-part message in MIME format. ------=_NextPart_000_000D_01C413ED.5C3F84A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Greetings: I am trying to derive the most reliabile absolute accuracy solution for = a local survey network using Gama adjustment. The local survey network = is a small survey network (4 to 6 points 40 to 60 metres apart) with = direction and distance observations derived from photographic image. = The directions have a standard deviation of about 8 minutes and the = distances 5 centimetres. The Gama adjustment works well with a one = "fix" and "Adj" point. I observed multiple autonomous GPS positions and meaned them for each = point. The autonomous GPS coordinates showed an average of 2.2 metres = off the known (correct) absolute coordinates from the points - the range = differences 1.0 to 4.0 metres. I seeded the Gama adjustment with these = autonomous GPS coordinates as "free" and ran Gama. I understand that = this treats the coordinates as unknown parameters and adjusts the free = seeded coordinates. As a least square adjustment is done I presume this = will minimize the residuals for these autonomous coordinates. I did a compare of the adjusted Gama coordinates with the true = coordinates. The mean of the comapred adjusted to true coordintes is = 1.7 metres - the range differences 1.6m to 1.9m. This seems to be a = good improvement. My goal is to determine the best procedure for using/integrating the = autonomous GPS positioning observations of multiple points of a local = survey network along with the relative survey measurements of the local = network. Has anyone else done any research similar to this? If so, I = would be interested to see your summary results.=20 I will do some more testing. The automous GPS unit is only $150. I am = looking for a way to optimize the global positioning and reliabitlity in = using the autonmous receiver. I will also test this network using a = WADGPS system that was recently rolled out to cover all of Canada. The = receiver/communications device will be ported with a PDA device and the = positions for the network will be meaned. I expect to be able to obtain = metre level global positions for the local survey network points. Any comments will be appreciated. Regards, Jim Sutherland Victoria Canada ------=_NextPart_000_000D_01C413ED.5C3F84A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=3DContent-Type content=3D"text/html; = charset=3Diso-8859-1"> <META content=3D"MSHTML 6.00.2800.1400" name=3DGENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=3D#ffffff> <DIV>Greetings:</DIV> <DIV> </DIV> <DIV>I am trying to derive the most reliabile absolute accuracy = solution=20 for a local survey network using Gama adjustment. The local survey = network=20 is a small survey network (4 to 6 points 40 to 60 metres apart) with = direction=20 and distance observations derived from photographic image. The = directions=20 have a standard deviation of about 8 minutes and the distances 5=20 centimetres. The Gama adjustment works well with a one "fix" and = "Adj"=20 point.</DIV> <DIV> </DIV> <DIV>I observed multiple autonomous GPS positions and meaned them for = each=20 point. The autonomous GPS coordinates showed an average of = 2.2 metres=20 off the known (correct) absolute coordinates from the points - the range = differences 1.0 to 4.0 metres. I seeded the Gama adjustment = with=20 these autonomous GPS coordinates as "free" and ran Gama. I = understand that=20 this treats the coordinates as unknown parameters and adjusts the free = seeded=20 coordinates. As a least square adjustment is done I presume this = will=20 minimize the residuals for these autonomous coordinates.</DIV> <DIV> </DIV> <DIV>I did a compare of the adjusted Gama coordinates with the true=20 coordinates. The mean of the comapred adjusted to true = coordintes is=20 1.7 metres - the range differences 1.6m to 1.9m. This seems = to be a=20 good improvement.</DIV> <DIV> </DIV> <DIV>My goal is to determine the best procedure for = using/integrating=20 the autonomous GPS positioning observations of multiple points of a = local=20 survey network along with the relative survey measurements of the = local=20 network. Has anyone else done any research similar to = this? If=20 so, I would be interested to see your summary results. </DIV> <DIV> </DIV> <DIV>I will do some more testing. The automous GPS unit is only=20 $150. I am looking for a way to optimize the global positioning = and=20 reliabitlity in using the autonmous receiver. I will also test = this=20 network using a WADGPS system that was recently rolled out to cover all = of=20 Canada. The receiver/communications device will be ported with a = PDA=20 device and the positions for the network will be meaned. I expect = to be=20 able to obtain metre level global positions for the local survey network = points.</DIV> <DIV> </DIV> <DIV>Any comments will be appreciated.</DIV> <DIV> </DIV> <DIV>Regards,</DIV> <DIV> </DIV> <DIV>Jim Sutherland</DIV> <DIV>Victoria Canada</DIV> <DIV> </DIV></BODY></HTML> ------=_NextPart_000_000D_01C413ED.5C3F84A0-- --===============0095662343== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Info-gama mailing list [email protected] http://mail.gnu.org/mailman/listinfo/info-gama --===============0095662343==--