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Greg McCambley (pelicans)
Posted on Saturday, March 18, 2006 - 06:55 pm:   Edit Post Print Post

I hope this doesn't sound like an infomercial, but I was intrigued by this technology and was urged on by the lineups to write something on this subject. There are many competing hardware and software products regarding GSP, this is my experience with the ones that I purchased, so the review is limited but still interesting.

I am referring to GPS technology and its application to Digital Garmin maps, Google Earth Plus satellite surface projections and as 3D terrain models in formZ.

Note: for $400 the accuracy can be as tight as 10 feet, for $40,000 the accuracy is close to an inch.

this is the GPSmap 60CSx from Garmin, acquiring satellites, after acquiring 4 satellites the tracking goes from 2D to 3D and as more connections are made the greater the resolution or accuracy

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The combination of a handheld outdoor GPS Mapping tool: i.e. the Garmin GPSmap 60CSx, a digital basemap transferred to this tool/hardware (60CSx) and the software that manages that information (the digital position, time, height and direction information etc.) that is recorded, stored and then downloaded to your Map Management/Design software, in this case "MapSource" by Garmin International.

The information from the GPS unit imports into the software "MapSource" in a propriety format, but its result can be saved out as gdb, ,mps, txt, dxf, or gpx (Note DXF). The data is viewed on the Mapsource software GUI as Way-points, Routes, or Tracks, with a varied selection of Topo or City Route mapping making up the changeable but active background. Only the Way-points, Routes or Tracks need to be imported onto the software. Note the Maps and their delivery to the hardware GPS unit (topo, street, or lake and ocean) are also managed by the MapSource software.

the lunch hour walk in the park

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A profile elevation of the total track

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Here is an example of a walk I took at lunchtime. If I click on any point it will tell me the local time that point was created, longitude, latitude, height above sea level (x,y,z). There are other facits like the speed, average speed, time stopped, area, length of track, a height profile, etc, etc, etc. But what I am most interested in is the final DXF data to bring into formZ.

But first see this track and way-points image from "Mapsource" superimposed on Google Earth "Plus", The "Plus" version of Google Earth costs $20 US per year and it allows one (non commercial user) to transfer the GPS data from i.e. "Mapsource" via pulldown menu selection directly to Google earth. Note: it also allows you to fly that tract, or route. Here is the same path in Google Earth Plus. (at a slight incline in the viewpoint to present the subtle relief in the satellite photo and its terrain. Note: there are three main versions to Google Earth: they are Google Earth (free), Google Earth Plus, and Google Earth Pro. (free- $20 - $400+ any plugins)

Make this selection from the pull down main menu of MapSource

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in Google Earth Plus

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When imported the DXF image was 3,700 scale feet away from the reference plane in formZ,(Calgary is 3,700 feet above sea level) so initially the imported image is some distance from the reference plane.

DXF export settings from MapSource

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Here is the path I took as a translation from the .dxf file and as viewed in formZ

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I am going to complete the terrain 3d model of the park walk as time permits.

I see this GPS technology as a handheld version of the MicroScribe tool "tip" but on a larger scale, that has a relative 10' accuracy. You can carry it in your hand, attach it to your mountain bike,boat and plane or stick it to the roof of you car, and have it directly connected to your laptop in your car, giving you voice over direction and routing information.

I feel it has great potential, I thought someone else might also.

Regards, Greg McCambley

In Memory of Kenth Agurell

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Reynold Dodson (reynold)
Posted on Monday, March 20, 2006 - 10:11 am:   Edit Post Print Post


I have a Garmin GPS and I got to try this.

One question: does the altitude component of your data come from the altimeter (i.e. barometric pressure based) or from the GPS system (i.e. satellites)?
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Greg McCambley (pelicans)
Posted on Monday, March 20, 2006 - 12:10 pm:   Edit Post Print Post

If your base map is Topo and not Street Map routing, that is a very accurate option (if your GPS doesn't have an Altimeter like the CSx). You don't have to worry about actually walking the line, you can just draw a straight or complex route on the topo map and then profile it. i.e. you can profile the US or Canada in seconds.

The Altimeter in the GPS is accurate, more so than the height accuracy of satellites (+/- 90') (as they are never below your position unless your in the air).

I feel the altimeter is more for jumping from a plane, as there is a utility in the setup section called "Jump Master" with slope and altitude calculations.

Even with an altimeter I would still use the datum derived from the underlying topo map.

The topo would also be my first map choice as it also comes with a basic but dated street/highway overlay. Then for navigating streets in strange or large cities, choose "City Navigator v7" recently updated in june 2005.