Hi Caroline,
I'll interject with some field experience with WAAS since up here in AK, geostationary satellite visibility is hard to come by. Lane's estimate is quite conservative from our extensive tests. Be happy to share WAAS only data with you, but if you do the right thing with navigation data (probably extracted from ESRI software right?), then the datum is the biggest hurdle (besides getting the antenna as high as possible). 60 cm horizontal is easily achieved.
1. WAAS is in "WGS84" datum. I say "WGS84" because it is really not, but in ITR2014, but the differences in those reference frames with the gear your using can't be seen.
2. Since this is a navigation question then, and knowing your incoming signal from WAAS is "WGS84", you must shift your ESRI data that may be likely in NAD83 to WGS84, then load it into the receiver. Transformation is key - in ArcMap/Pro, use the highest shifter observed in your data frame, to go from NAD83 to WGS84. Send your grid data to Trimble in that reference frame. Now your aligned with the space based augmentation.
3. Key to WAAS on TerraSync is to jack up the WAAS setting from 1 minute to 4 minutes. This allows TerraSync to chill out up to 4 minutes if it last heard a WAAS "chirp". Be sure to set in logging settings (in TerraSync) as the first correction source as WAAS, uncorrected as second.
4. Lastly, monitor the status bar. lock onto WAAS (the blue radio icon) before you start on your grid. The only way to do this is holding the reciever up or, better yet, connect to a good Trimble antenna (Tempest, Zephyr) so your antenna is as elevated as possible. You stand on the southside of your receiver, then your body is blocking WAAS.
Depending on your geographical location, that signal is 15 to 30 degrees above horizon. Confirm that in Terrasync on the Skyplot. The WAAS satellites are seen with that aircraft looking icon.
My tests with Geo7x, TS professional will put you solidly at 60cm, if you did the right thing in GIS, AND controlled for the reference frame (WGS84) which you are in in the field.
And on the back end, your field data you do collect can be post processed (FOR FREE MIND YOU), using post processing differential. A test, like others we do up here on survey control (see below) exposes what you really can do with the most advanced GIS device ever (i mean - ever) created. The technology built into the Geo7x running TerraSync is the best in the buisness. Sadly, there is no Trimble out there with this capacity and power. Were waiting right Lane?
PostProcessed accuracy to Survey control. Datums done correctly. You hit in 3 dimensions under a foot. For Free, no subscription!! and all-in-one device for field effiency!
Good luck.
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Joel Cusick
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Original Message:
Sent: 10-07-2021 07:33
From: Caroline Bruyere
Subject: Trimble Geo7x accuracy
Hello!
I will be using the handheld Trimble Geo7x to navigate a grid I have loaded on the device.
I was wondering what is the accuracy without internet connection? (open field)
How can it be improved without a private VRS/RTK subscription? Is simple internet connection enough?
How about at DGPS subscription?
I am fairly new at this.
Thank you!
Caroline
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Caroline Bruyere
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