GPS_offset tricks?

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09-21-2017 01:18 PM
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Greetings,

I have a data set of about 20,000 records (points). In the attributes, for each record I have Lat/Long coordinates (WGS84), GPS timestamp, and a field with values (decimal numbers) which were collected and logged in the following manner: 

I carried the GPS antenna on my back with the GPS handheld in hands, which acted as the data logger. The instrument that records the data was wired to my data logger, and it was a distance away from me, being pulled by my other hand. The instrument generates 5 records per second, hence why that data set is so large. I was walking in a straight line, in both directions (back and forth), at 1 foot interval. 

THE PROBLEM:

The values, recorded by the instrument, are mapped wherever the GPS antenna was at that time.  If the distance between the instrument and the GPS antenna is 2 meters, for example, then there is a 2-meter offset that needs to be corrected. In other words, the GPS-plotted points need to be readjusted 2 meters back (location of the instrument). That being said, it's the location of those values collected by the instrument that matters, not the location of the GPS antenna. 

THE ASSUMED METHOD:

I believe one way to correct the GPS offset is to figure out the bearing (direction) of each of those points, and then have the script pull the plotted points 2 meters back, each point based on its bearing. 

THE EQUIPMENT:

I have fair knowledge of ArcMap but have little-to-none experience with coding/scripting. I do not know how to figure out the bearing of all those points. My ArcGIS is 9.3, with Spatial Analyst and 3D Analyst extensions. The PC is fairly new and beefed up enough to handle big operations.

Hoping this would present a challenge for someone more knowledgeable. ANY ideas, hints, clues, answers would go a long way!

Thank you in advance!

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MVP Esteemed Contributor

It sounds like you want to buffer on one-side which is possible if you convert your points to a polyline, perform the one-sided buffer.  Obviously the buffer side would be chosen by you to represent the direction that you want to offset.  This requires an advanced license and I am not sure 9.3 even had that capability