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We recently walked a fence perimeter with a Trimble Ranger, auto-logging positions at 5 second intervals in a generic point file. The exported file acknowledges over 800 points, but only displays the specifically recorded points (far fewer than 800). Is it possible to access the internally logged points and convert/display them as features in Arc?

My apologies if this is common knowledge, I've had no luck in over an hour of browsing forums. Thanks in advance for any help.

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3 Answers 3

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It's easy to confuse positions and actual points which are different things. Positions are logged to a single point, which are then averaged to produce the final location of a point. If you recorded a bunch of positions that followed a fenceline into a single point you'll probably have some trouble getting those into the format you wanted. This is done because the position reported from the GPS receiver drifts every time it is updated, due to lots of factors, which are the subject of a whole other post. The GIS software then takes all of the positions you record for a point and essentially averages them into a final point location. Here's a relatively crude attempt to display this graphically. This is why it's always a good idea to collect a large number of positions for every point - the higher the sample size the more 'accurate' the final position. (Sidebar: If you plotted the drift of your unit for each position reported, after a while you'd have a cluster that has a diameter approximate to the reported 'accuracy' of your unit. ie-3 meters.)

enter image description here

As @Mapperz mentioned you can use the Trimble GPS Analyst extension to view the individual positions you logged, but you will probably have to convert them into points manually as (to the best of my knowledge) you cannot directly convert positions into points.

A better data collection strategy would be to record a line or polygon feature with your Trimble. That would convert each position into a vertex along the line or polygon boundary and result in a feature that showed each position you recorded without having to use special extensions to get into you data.

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Thanks for your response as well, Kevin. This helps clarify what's happening, and confirms what I've been suspecting, that I'll have to re-walk the line (which isn't that onerous a burden). The line isn't a closed square, it's more of a U shape. Would I be better off marking as a line or poly? –  Rob C Feb 4 '13 at 15:08
    
Glad to hear it was helpful! It depends on what you want to represent. If you are interested in the just the fence - I would record it as a line. If you are interested in the area enclosed by the fence, then I would record it as a polygon. –  Kevin Feb 4 '13 at 15:12
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With the Trimble GPS Analyst Extension for Esri ArcGIS for Desktop Software you should be able to connect your Trimble Supported formats

Base file formats
Hatanaka (Compressed RINEX)
RINEX
Trimble DAT format
Trimble SSF format

http://www.trimble.com/mappingGIS/gpsanalyst.aspx?dtID=applications&

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Thanks for the quick response, unfortunately the $2,000 price tag is a bit steep for us. I guess I'm just surprised that there isn't a more common workaround for this. Regardless, I appreciate the help. –  Rob C Feb 4 '13 at 15:06
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Trimble makes a dedicated software package for this (other than Trimble GPS Analyst), Pathfinder Office, which will let you do this and lots of other things with your Trimble files. Contact your Trimble rep (if you bought the unit from them) and they may be able to hook you up with a free or discounted copy.

You can export positions that aren't part of a feature (like yours) to a shapefile by checking the "Include Not In Feature Positions" box during export:

enter image description here

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