Hello again
I've been tasked with trying to figure out how to improve the accuracy of our handheld Trimble Geo XH which is the 6000 series, every time we use it in the field it states an accuracy of less than 1 foot both H and V. However when you import it into cad it shows up roughly 5' off. So I did a few test using our R10 to compare to. And it is still 5' off roughly. I was wondering what I can do to improve the accuracy. I have the coordinate system set to NAD 1983 Cors 96 both observation and data transfer for corrections.?ÿ
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thank you for any help
Did you differentially correct your data? Aka post-process?
5ft is reasonable accuracy for raw data, the numbers the geoxh is showing on screen is not the raw accuracy but rather its the accuracy expected post proceesed.
How long did you occupy the point??ÿ I have used them in the past I always take at least a 30 second shot and post process with Trimble GPS pathfinder.?ÿ it will get you within a couple centimeters.?ÿ?ÿ
I am starting to use longer occupation points, also I have found that whoever had set this up before had different coordinate systems. So I'm setting it up both on the hand held and the pathfinder office to WGS 1984 to see if this will bring me match my RTK shots.?ÿ
I am going to speculate that this is a US Survey Foot versus International Survey foot issue either your handheld is set for International feet and the provided coordinates are in US Survey feet (or visa versa). The scalar difference in Colchester Vermont is about 3.3 feet SW/NE. I am going to bet that your misses are always in the same general relation to the record location and that the direction of the miss is around N 65?ø E or S 65?ø W.
Trimble refuses to let go of WGS 84, despite the fact that almost nobody in CONUS uses it.
I set my Trimble projects up with global to local transformations of all zeros. My work is all done in NAD83 of one flavor or another.
Yes Randy to answer your question all points are off around 5.36 ft +/- to the NE. This is something that can be resolved by changing from feet to US Survey Feet??ÿ?ÿ
It could (likely?) be a datum issue, they could be ITRF positions. I am not familiar with the Geo, but when I use my R10 with RTX, the positions are stored as ITRF08 epoch 2005.0 positions. I use HTDP to transform to NAD83 (2011) epoch 2010.0 positions.?ÿ
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That would be the first thing that I would try. If your handheld is coming in NE of your RTK then the Handheld is set for International feet (If this is the problem) as International feet are larger than US survey feet (1.0 US Survey Foot x 1.000002 = 1 International foot). Change the Handheld to US Survey feet and most of the discrepancy should go away.
Are you post processing??ÿ
Are you using the internal antenna??ÿ?ÿ
Here's the follow up so far. I found that changing it from international feet to us survey feet made very little difference. However what I found that changed the game and made the points come within .1 +/- where my RTK shot are is in the exporting from pathfinder. So I collect with WGS84 and post process using WGS84, but when I export to AutoCad I have to export on NAD as that's what our Cad projects are set up on. Once I did that everything checked out well. To answer the above question we are just using the internal antenna.
That being said, what are everyone's thoughts on collecting data with uncorrected GNSS vs. using SBAS?
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