<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
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</o:shapelayout></xml><![endif]--></head><body lang=EN-AU link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>I think this is a great discussion. I have been working with GPS’s for well over 10 years and I have a modest paper with an image showing GPS tracks from my phone (Galaxy Note), a Garmin Montana and my Trimble Geo7X that shows these issues with accuracy. I happy to share if someone can explain how to do so.<o:p></o:p></p><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>I was thinking, Nicolas Cadieux, that I would trust an old crusty surveyor with a Theodolite and a good set of base stations more than my phone because surveyors are taught ways of avoiding errors and distributing uncertainties that others such as myself don’t know. All survey is done with parameters of accuracy and surveyors are trained in understanding this more than non-surveyors such as archaeologists for example. An experienced surveyor knows all the techniques.<o:p></o:p></p><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>That being said, surveyors readily embraced the new positioning technology from the 1960s onwards and the reason we have so many new datums and projections is that the new surveying technology has allowed the geoid to be modified so it more correctly models the actual shape of the earth.<o:p></o:p></p><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>Having just gone into the matter of purchasing the best surveying equipment for archaeological projects my experience is that we had issues with cm accurate GPS in urban areas due to the canyon effect of signals bouncing off the infrastructure which indicated using a Total Station in urban areas but out of the city (rural Australia) we have issues with finding control points to tie a Total Station into which indicated that using a cm accurate GPS would be better. In areas around the fringe of Sydney there are steeps gullies and forest canopy so a compo of GPS to set control points and Total station was indicated. The GPS would locate control points on the geiod and the Total station would located itself by resection from the control points and then could record our locations.<o:p></o:p></p><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>The cost of a GPS + Total Station solution was c$A100000 when you add subscriptions for software, access to base stations for real time corrections, annual maintenance, and staff training. This is a huge cost for a smallish business or project. There seemed to be no alternative to being locked into a particular manufacturer’s ecosystem – Leica, Topcon, Trimble …etc. Ultimately we did not proceed with the purchase.<o:p></o:p></p><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>The other option is the Trimble Catalyst model where you BYOD and purchase from Trimble the aerial and software access – this varies in accuracy and time of availability so you can purchase as much or as little accuracy and time using the software as you need. So long as you have the money.<o:p></o:p></p><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>I should also point out that your GPS should be able to read and process more than just GPS and GLONAS satellites. The Japanese Quasi-Zenith Satellite System for example is optimised for the steep terrain and urban canyoning typical of Japan. There is also the Galileo navigation system, funded by the long suffering European tax payer and the Chinese Beidou/ Compass system. I can see these satellites on my GPS and on my phone, but it is not clear to what extent the units actually read the data and process it rather than simply tell me it is there. <o:p></o:p></p><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>Also the physical configuration of the phone adds an error in that you need to know where the aerial is located and place it on the point to be measured rather than simply wave it around. <o:p></o:p></p><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>My sense is that the technology is progressing at a slow pace largely due to lack of consumer demand. I thought cameras would all have inbuilt GPS in them by now but only the “extreme” models do. Multi-Global Navigation Satellite System chips are slowly being deployed but they are not a big consumer item. Clearly more people but a phone for its camera rather than its accurate GPS. <o:p></o:p></p><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>I conclude that we have to live with inaccuracy or pay thousands of dollars to reduce the inaccuracy to 1-2cm. It seems to me that so long as the inaccuracy is known and accounted for, this is not so much of a problem. It is better that we are aware of inaccuracies and lack of precision than assume that our phone GPS’s are precise tools.<o:p></o:p></p><p class=MsoNormal style='margin-bottom:8.0pt;line-height:106%'>As with all technology though, watch this space. <o:p></o:p></p><p class=MsoNormal>Cheers<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><b><span style='font-size:12.0pt;font-family:Papyrus;mso-fareast-language:EN-AU'>Dr Iain Stuart<o:p></o:p></span></b></p><p class=MsoNormal><b><i><span style='font-size:12.0pt;font-family:Papyrus;mso-fareast-language:EN-AU'>JCIS Consultants <o:p></o:p></span></i></b></p><p class=MsoNormal><span style='mso-fareast-language:EN-AU'>P.O. Box 2397<o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-AU'>Burwood North<o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-AU'>NSW, 2134<o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-AU'><o:p> </o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-AU'>(02) 9701 0191<br>(0413) 380116 (m)<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>