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Prism offset for the Trimble MT1000 and AT360?
Posted by kjac on November 23, 2020 at 2:31 pmIf I want to shoot a building corner with these prisms what offset distance do I add? It looks like the MT1000 is 0.15′ from what I am reading. How about the AT360?
rj-schneider replied 3 years, 5 months ago 5 Members · 4 Replies- 4 Replies
Measure from the physical center of the prism to the corner you’re measuring. With the MT1000 I typically use 0.15′ on outside corners if I’m able to get the prism tight against the corner and perpendicular to the instrument’s line of sight. If I’m leaning in at an angle the offset is greater. Inside corners often require two offsets, one out to the corner and one left or right to the corner and they’re always dependent on the angle from the instrument to the corner. I always keep a short box tape with me when shooting offsets so I don’t have to guess at the non-standard offsets.
I always kept a mini prism in my pocket and just switched the prism type over when I needed to shoot something direct like a building corner. The S5 tracked and shot that with no issues. Even walked corner to corner holding the prism facing the instrument so it would track.
I like the mini prism for corners too. But (back when I was allowed to go in the field) I found myself taking far fewer corner shots than I sued to. With the cameras integrated in the robotic TS, it’s easy to stitch a handful of reflectorless shots along the building wall, create fit lines in CAD and fillet everything. Or without the camera, spend 2-3 minutes at the instrument right before I broke setup and grab all my building line shots sighting manually.
With good procedures, when I did take corner shots carefully and compare them to the reflectorless-generated corners, I would see maybe 0.05-0.08′ of difference at most…good enough for most of the work I do.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil PostmanQuick google search doesn’t turn up any results for a spec sheet
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