Hi again,
This is an experiment I have made to demonstrate the potential precision of a single commercial-grade GPS engine used to locate a PPM survey and the capabilities of our MarkIV system to support very large field gradients.
I made this test on a dirt road in the countryside. I went up and down the same road and I crossed the path of a large gas pipeline running under the road. Thus, I went twice over it. See the large field gradient and still, I only got a single bad reading. The other large gradients are due to my car parked along the road. I passed at three or four meters aside of it.
With an HDOP of average 0.8 and 11 satellites in view, the GPS tracking is perfect. On one leg of the path, I walked exactly on the same side of the road and on the other leg, I walked on the other side. This is perfectly clear on the XY plot. Finally, I walked back to my car along the road but at 3meters aside of it.
- The first picture shows a KML file as displayed by Google Earth with some of my annotations. You can clearly see that the precision of the GPS fixes is more than sufficient to locate any potential target within a radius of one meter.
- The second file is a screen dump of a Wndows program I have written to review such a GPS-based survey file. The field gradients are displayed as a time-based barchart and as a XYZ plot using dots of varying colours and radius.
Both plots are responding to mouse clicks by giving the corresponding lat/long and B field values.
- The third file is the survey file itself loaded as a zipped Excel file with the plottings of its main data.
Willy
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« Last Edit: February 09, 2011, 09:29:28 am by willy bayot »
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