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Sub-meter resolution GPS?

Started by clearcut, November 08, 2021, 10:12:31 PM

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clearcut

Been thinking that a sub-meter resolution GPS would be useful for finding corners, and flagging boundary lines and water course protection zones. 

Yes, I am aware of how much they cost, but that could be justified considering how long I searched for a couple of corners today. Found one by literally tripping over it.  Another appears to be buried deep in slash. For unknown reasons, my GPS drifted around widely, more than I've ever seen it do before. 

So your thoughts or experience with a field worthy unit would be very much appreciated.

Carbon sequestered upon request.

SwampDonkey

You'll need good sky coverage unless you have a base unit out in an open field and a hand unit as a rover. You're then talking big bucks. Might as well become a surveyor and earn some real money to justify it. ;) You're probably down in some gullies and canyon terrain if the unit you're using is not getting a good lock. If you have just a handheld with real time DPS and no base, you will not be any better off, you could be standing there a long time to get a lock, that time increases with the higher the accuracy.

Lucky back here in NB I have not had trouble finding lines or corners with a Garmin Map64S. I have all the boundary lines loaded on it. I would not use it to establish a line, just to find evidence, since it's not a surveyor instrument and I'm no surveyor. And I have found discrepancies between ground evidence and mapping, a disclaimer from the government states there are possible errors and can not be used as evidence. I do some mapping of blocks on ground owned by one mill, and it is well known that lines move when this mill buys new ground. I've seen lines move 20 feet, in their favor. One time they thought I was over the line on their neighbor. The aerial photo of their logging and their own map showed the line swerved onto the neighbor and back. I never heard another word. :D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

BradMarks


foresterdj

Go to www.fs.fed.us/database/gps/mtdcrpt/accuracy/index.htm

real test results in different canopy levels for many devices. Very few give true sub-meter unless in the open. That said, if you are harvesting wood of any value and your options are leaving a half chain to 1 chain buffer to an estimated line vs the expense to get closer (knowing you are not surveyor correct) it will not take much to pay for itself.

Have myself found Trimble Geo 7x with WAAS, using TerraSync for the navigation (the off tracking feature for running lines) the best balance between crazy expensive surveying equipment and forestry line estimation. Pick your days. For heavy canopy forest types I like doing this work in leaf off, fall to spring.

SwampDonkey

I've used Trimble GPS a few years, mostly in young growth, sometimes to establish cruise points. In short, young, growth that we thin, I've not found them any more accurate than a Garmin 64S that I have used now for 5 years. I get paid for my GPS maps, and worth more than the GPS itself by the end of the week. That includes running lines for a crew of clearing saw operators across the block 40 meters apart, to determine the areas in each work strip. Crew men get paid by the area cut. Way better than string box and compass traverse. The GPS system replaced the string box 23 years ago, never looked back. And I've traversed a lot with string box and compass, used that 10 years before GPS came online. For the Trimble I have, the province has set up base stations to download corrections fee of charge. It did not do real time corrections. This was a $6000 device, for real time, pretty much double. :D Garmin? $700 ! Close enough for government work they say. :D :D I use the property maps and road maps from the government and made my own custom GPS layers. The actual GPS work is a track file.

Just a simple map. I show the aerial here so you can see stand boundaries. Any places not up to the edges is usually a raspberry area or residuals not included. I don't usually use the aerials for this type of work, all they want is a perimeter file at the mill, boss wants perimeter and strips.





Pays the bills. ;) The Garmin 64S can take aerials, but I don't need them out in the woods, I trace a work map by following stand boundaries on my GIS and Google map (aerial photo) overlay and use it as a guide when working on the ground. The mill gives us paper maps and it isn't hard to draw the shape off the photos. I only need the property lines on private ground because on crown or mill ground the lines are well marked. On crown it's vast areas with no private in the middle of it.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

foresterdj

I would add to my previous comment that for interior work collecting lines for harvest boundary, plots, roads, etc, just about any GPS is good enough at a few meters +/-. Often use the GPS on my phone with the Avenza App for collections. The GPS error is narrower than the boundary line symbology used on any map.

Only for trying to get close to a property line, if nothing else to relieve neighbor concern, is a device like a Trimble Geo 7 or Geo 6000 worthwhile. These devices running real time correction, are often estimating 20" to 3.5' accuracy. Very commonly within 1 to 3 feet when looking for existing pins, sometimes buried in litter. Thinking a recreational, or phone GPS is that accurate is a fantasy.

SwampDonkey

That depends on the accuracy of the map overlay to. I've seen a marked lines once in awhile be several feet different than the GPS map for sure. Wouldn't matter how accurate the GPS, off that much. I've found a lot more to be pretty bang on within a 1 or 2 meter on a recreational GPS. I don't have a bit of trouble proving it. I've found a lot of legally marked lines with a lot of wain to. I can challenge anyone to keep a transit dead on those lines. :D Accuracy isn't just GPS errors, it's mapping errors and ground errors from those who deem themselves the gate keepers. :D I have seen line locations move on a few lots with different legal surveys to. I certainly would not use a recreational GPS to survey with though, they just have too much multipath to hold a straight as an arrow line. And it's not legal to survey and establish a line location without the credentials.

I can show you where my pins are precisely, except one, with my Garmin, by using a map provided online by the government. A map they say isn't legal to hold up in court. Then where are the legal ones, up in the cloud? :D :D Yep, my pins are all placed by a legal surveyor. The one pin mentioned above isn't mapped, but I can walk to it precisely, no map, no GPS. I know it is there with the surveyors name on it, it's not in the 'system'. :D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

xkiwi

DIY so not field worthy but u might get a geek to help you

What is GPS RTK? - learn.sparkfun.com

About $1000 after battery packs , antenna etc and yields better than 1inch. On my list try out this winter if sunny NORCAL weather changes to rain and drives me indoors...

Old enough to know better but still confused

wkf94025

I have played around with RTK GPS gear on a fixed wing drone project that is still on the bench, yet to maiden. Per previous post, gear is under $1,000.  I recall $700 for the pair of RTK GPS receivers, a few years ago. One stays on the ground, one in the air, and post processing of their data to get within a centimeter in x and y, and a few cm's in z. Cool tech. My project goal is a long endurance 2 meter wingspan twin motor mapping drone, capable of cm-level mapping a thousand acres in one flight.
Lucas 7-23 swing arm mill, DIY solar kilns (5k BF), Skidsteer T76 w/ log grapple, F350 Powerstroke CCSB 4x4, Big Tex 14LP and Diamond C LPX20 trailers, Stihl saws, Minimax CU300, various Powermatic, Laguna, Oneida, DeWalt, etc.  Focused on Doug Fir, Redwood, white and red oak, Claro walnut.

John Mc

So what is the recommendation for a landowner looking to take the next step up from a consumer GPS to improve accuracy? I'm in hilly (but not mountainous), heavily wooded terrain. I'd love to reliable get within a meter or so. It would be great to be able to do this live, but would consider doing it with post processing

NOTE: I have never done any post processing, so have no idea what is involved with that. Any beginner guide to that sort of thing would be greatly appreciated.

John
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

beenthere

south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

reride82

Sub-meter accuracy is hard in full canopy even with survey grade. My sub-centimeter receivers have a hard time in full canopy, which means we are either removing trees to get a better sky view or surveying into our point via total station. It depends on the landowner, and the timber quality. A good Douglas Fir stand, I won't remove a tree over 6" DBH. but Aspen is free game! :D Don't discount the string box and Compass/Brunton combination, I still break it out once every few years. I'm envious of your GIS data for being that reliable, I retraced a few sections this past fall/winter that had mostly been un-surveyed since the GLO(Government Land Office) surveyed them in 1893, there a few that were 70'+ feet from record. The problem with GIS is the quality inputted into the system reflects the data output.

Levi
'Do it once, do it right'

'First we shape our buildings, then our buildings shape us'
Living life on the Continental Divide in Montana

SwampDonkey

John, the GPS which is $$thousands, then the software which is $$thousands more to even run it. And you need sky, no canopy much. I've run earlier models and you could stand there a long time to get a lock. And this would act like a rover to a base station if any real surveying was done with accuracy. That's $$thousands more.

Trimble GEO7X, Arcpad or Terrasync software, and Trimble GPS PathFinder Office.

For my line of work, I am not surveying lines. I am just measuring land, but I do have boundary lines loaded to help find evidence. I will compass down spotty lines, if a lot of trees are gone or fell down after clear cut. We are on mill and public lands so lines are all painted and surveyed. I've never had a company dispute my areas when using a Garmin GPSMap 64s. I use ExpertGPS and Maptitude GIS on my laptop to manipulate the files, convert to different formats and draw the map. If I want a custom GPS map I make it with Mapwel and load it to the GPS (roads, boundaries, streams, cut block perimeters). I can import GPX and KML into it. ExpertGPS can Import/Export lots of formats including shapefiles.

Up this way, all post processing with Trimple Pathfinder Office you go to the closest station, which our government has established across the province. There will be a URL and you just add it to the software. The software downloads the data once you set it up in the software, it downloads your collected Trimble files from your GPS and the correction files off the site and corrects your files. The corrected *.ssf file will have a *.cor extension. You can export as shapefiles, maybe other formats to.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

SwampDonkey

Here is a document for setting up a new base station in GPS Pathfinder Office, this program does the post processing. It was an older version of the program and uses NB base stations in the example. Pathfinder uses a sub program called Differential Correction Wizard.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

Kodiakmac

QuoteI've seen lines move 20 feet, in their favor...
Yup.  99 times out of 98! :D
Robin Hood had it just about right:  as long as a man has family, friends, deer and beer...he needs very little government!
Kioti rx7320, Wallenstein fx110 winch, Echo CS510, Stihl MS362cm, Stihl 051AV, Wallenstein wx980  Mark 8:36

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