Land Surveying 101 - Prism Selection

[@Panther-]

Most comprehensive guide on this topic by a mile,excelent info thanks.

[@ron6625]

I would like to send this video to my boss. I've considered spending my own money on a GMP101 just to make my own life easier. I don't think the bosses full grasp that if you're looking for a consistent under 3mm accuracy from different setups on different days over long periods of time, that you cannot expect things to work properly if you allow your layout distances to be as great as 30m away. You're already starting off with a resection that is not as tight as it should be, even if the numbers tell you otherwise. That's why limiting number of setups, distances to layout, and having checkshot locations peppered throughout the project, is how you keep things tight. Better gear, better practices, reduces headaches far more than trying to fix things. Instead, they insist on spending more and more time doing traverses. It's like, at a certain point, does doing another traverse really help, when you're not getting repeatable resections off those traverses anyways? Garbage in, garbage out. I'm a big fan of Trimbles traverse prisms. Solid, don't get to use those enough. And I've noticed that the Leica GRZ101 is still better than the knockoff versions of the GMP111' s or the non-nodal miniprisms. They're pretty consistently within 2mm of my points. Using a more old school approach to surveying with an instrument man and a party chief, non-nodal prisms still have their place...They just don't have any place in robotics...which is basically all I do these days.

[@geodesta]

Excellente in depth content! I like it keep share it with us.

[@alexandrecote9494]

Wow! You must had put on lot of time to do that so nicely maded information video ! I have a university degre in geomatic and I'm a legal surveyor, I can tell that you are a real professional. You did cover perfectly the subject. Congratulations !!!

[@The3rdDimensionSurveying]

Thank you for the kind words Alex!

[@PJLogue]

100% agree. Excellent, honest, in depth summary of the subject. Thanks mate!

[@marknielsen9315]

Great series of content on accuracy, have gotten a lot new information from these. Thank you

[@elcuate1100]

Thank you for sharing, all your videos are verry helpful.

[@steveo4749]

Thank you for this deep dive in prism technology.

[@aidanburfield2670]

Finally I've have found a channel that really deep dives into all aspects of survey! This video in particular I found very interesting, when I first got into this industry we used leica robots, with their 360 prisms. But used the non nodal 64mm prisms on a prism pole for backsighting/traversing and wondered why we were getting horrible closures.. Finally they sprung for the leica traverse sets with the circle prisms and additionaltripods, difference of night and day how much our accuracies and closures improved.. There is a lot of truth about what you said.. you spend over 10k on a 3" instrument, then buy cheaper lower quality prisms. Thanks for sharing this content!

[@DavidBrown-lv6ox]

Brilliant, thank you

[@thesiborg]

Really love your deep dive videos mate! Just a heads up at 13m30s you state GRZ4 as having pointing error of 3.5mm and the GRZ122 at 6.2mm, think you have transposed the prisms there as at 14m25s you state the opposite 😉 Looking forward to your next video!

[@The3rdDimensionSurveying]

Great catch! You’re absolutely correct, the older GRZ4 is much worse and carries the higher total error.

[@orangejuicepony6881]

The 360 Trimble prism (large or micro) is primarily for keeping the instrument following you, once you settle on a mark like a grid line you always point one prism back at the machine. Much easier than trying to search and lock for every setout with a directional prism. Almost not error this way either.

[@PedroHernandez-tw4nz]

Congratulations, nice video and topic.

[@The3rdDimensionSurveying]

Thank you Pedro!

[@IMGeotechInstrumentacao]

Great content! Already following the channel.

[@TalibHussainAttari]

what a great video thanks a lot

[@ronnieclewlow1491]

If shooting control with the MT1000 what setting would you say is going to give the best results? Active, Passive or Semi Active? Seems like you lose vertical or horizontal accuracy in whatever settings you choose? Im not a fan of using a traverse kit as I used to get great results from the Leica glass with a pole stand. But not moved to a company that uses Trimble.

[@The3rdDimensionSurveying]

Hey Ronnie, Yea it's really a trade off like I mentioned the video. First of all, I wouldn't use that prism for control unless the control had a loose spec. If I had a differential level I would use the MT1000 under active mode to ensure a higher level of hz accuracy and then run a closed level loop through that and process both data set in Starnet. If I didn't have a level, you have to choose which is more important for the application at hand. Maybe shoe them this video and they may Change their mind? If they're against Leica trimble does make a round prism specifically for traversing. It's not cheap but looks nice.

[@neilrobicheau6228]

​@@The3rdDimensionSurveying I shot you a message on LinkedIn. Good to have another Canuck surveyor in Florida.

[@antvander4456]

Great video, one thing I wonder about is how much can you rely on the automatic locking to prisms from robotics, if you actually look through the instrument when it’s locked it often isn’t centred. If this is the case, how come people will do traverse surveys using the automatic lock and measures?

[@The3rdDimensionSurveying]

Great question, even though the crosshairs may appear to be significantly off center when using ATR, the total station optical line of sight is supposed to be pointed at the center within the spec of that instrument (or should be if its calibrated properly), I believe this has to do with error introduced from parallax at the eye piece. It would be a very interesting test to run a traverse with ATR and repeat that traverse again using manual pointing but keeping everything else the same. I suspect the ATR would win but you never know. I'll have to add this to the list of tests to run. Thanks for the comment!