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Not sure what to buy for basic precise coordinate information.

I am not interested in hiking, maps, altitute, barometer. I want to follow a straight line (my property lines). The cell phone GPS is worthless for this, especially as the land is wooded (rural area), and I get 1 or 2 bars on the phone. Perhaps the newer phones coming out, with dual GNSS chip and the ability to get both the L1 and L5 frequencys (see GPSTest app in case this is new to you), along with 5G, will be better.

From my survey map, I get the degrees, minutes, and seconds, and have calculated the degree (Ex s14,55'34"W =
194.926111111111). Obviously, hand held compasses cannot detect that kind of accuracy, so I rounded that to 195 (reverse is 15), but I cannot get that to line up with what I know should be the end point of the line. I put a line of stakes 50 feet apart on the line, and I can see then lined up backwards and forwards but they do not line up with where it should end. Big trees (where I cannot look back to see the lineup), throw my line off even more.

So, I am looking for more accuracy. Aside from very expensive survey equipment, can a hand held device (Garmin\whatever), give me the kind of accuracy that I am looking for, in particular, give me at least 2 decimal points
(194.93)?

I had written an Android app to calculate distance between two points, but again the GPs information is worthless. I understand that some devices can use bluetooth to broadcast so that a phone could pick up the information?

Thanks in advance.

Comments

  • Boyd 2043 Points
    edited October 2020
    Have a look at this thread:

    http://forums.gpsreview.net/discussion/31506/garmin-etrex-creating-a-trail-map-using-track-recordings

    Interesting that your survey actually shows coordinates. Or maybe I'm not understanding what you're saying? My survey identifies a starting point (such as a stake in the ground) and provides vectors to each successive point. For example:

    "...proceed North 65 degrees 50 minutes East, 374.56 feet to a point..."

    You might find this old thread helpful, especially the software that @RangerRushton posted.

    http://forums.gpsreview.net/discussion/comment/198851

    But, regarding accuracy, it will be interesting to see if the recently introduced GPSMap 65 series lives up to Garmin's claims

    http://forums.gpsreview.net/discussion/31512/garmin-introduces-the-gpsmap-65-series-and-gpsmap-66r
  • The 66 is the only one that specifically mentions the L5 frequency. Looking at the user manuals for the 65 and 66, their accuracy is 3.6 M or about 12 feet. So, it is looking like I am not going to find the accuracy that I am looking for.

    My survey, like yours, shows vectors. I got the S14,55'34"W =194.92611111111, by using the info on this link...https://support.goldensoftware.com/hc/en-us/articles/228362688-Convert-Degrees-Minutes-Seconds-To-Decimal-Degrees-in-Strater.
  • privet01 231 Points
    Only a survey by a surveyor will mean anything legally. All you'll do with a GPS is make yourself suspicious of things.

    The earth isn't flat so when a property description says go 500 feet, part of that might be up the side of a hill and not 500 feet in horizontal that simple math applied to a coordinate can come up with.
  • Boyd 2043 Points
    Here's a thread on a local website that might be of interest, one of our members got a used Trimble GPS for $150 to provide sub-meter accuracy for a personal project. Now, this is a professional device that he was already familiar with, it would not be user-friendly like a Garmin GPS or a smartphone.

    https://forums.njpinebarrens.com/threads/mapping-graves-with-a-trimble-gps.13430/#post-161215
  • I am going to try a different tack here. Instead of trying to purchase GPS equipment (of which even the newest Garmin devices will still only get to 3.6 M), I need a better understanding of how to adjust for magnetic north deviation. I am not sure if I should be using a different forum (if so please point me in the right direction), or, can this be addressed here.

    I have a survey map, I have the metes and bounds, I can calculate the azuimth degrees. I am right on the Mass\NH border. The survey is from 1994, there is nothing to indicate true north vs magnetic north, so my first question is... should I assume true north or magnetic north was used (there is just the one arrow pointing north, labeled December 1993).

    On this site..https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#ushistoric, I enter in my address, and it gives me Latitude 42, 49', 0", Longitude 71 9' 4". I select 1993 thru 2020, and it then shows me the years and Declination. 1993 is 15 58' and , 2020 is 14 30' W, so difference is 1.20? +\-?

    If the survey was using magnetic north, then I should be subtracting (?), 1.20 degrees (Ex: if it was 6.45 degrees previously, it should now be 5.?), fror my compass reading? Or should I be adding?

    Thanks for any help or direction.
  • Boyd 2043 Points
    edited November 2020
    what2buy said:

    I am not sure if I should be using a different forum (if so please point me in the right direction), or, can this be addressed here.

    I hope you get some input, but frankly it would surprise me. This is a consumer-oriented site where the majority of discussion revolves around Garmin automotive devices with a few posts about Garmin handhelds. And, unfortunately, we no longer see much activity here since people are moving away from dedicated devices to smartphones.

    Sorry, no idea what forum you should use. If it were me, I would consult a surveyor. I don't mean necessarily hiring one, just getting them to answer your questions. I mean, I have a friend that could help me out with this kind of thing, but surely any surveyor would help for a small fee. Then you would have some confidence in whatever work you do in the future.
  • Does the survey indicate who did the survey, and is the surveyor still around for you to contact?

    You brought up questions about magnetic north and true north. It could also be grid north.

    On declination, you said "1993 is 15 58' and , 2020 is 14 30' W, so difference is 1.20? +\-?" The declination is in degrees, minutes and seconds. If you want to express the difference in decimal format, it is about 1.47 degrees. You already observed that "hand held compasses cannot detect that kind of accuracy". The bigger problem would be trying to follow such a precise direction, especially in and around trees.

    I agree with privet01 that you'll likely need a surveyor for anything involving a legal issue.
    privet01 said:

    Only a survey by a surveyor will mean anything legally. All you'll do with a GPS is make yourself suspicious of things.

    The earth isn't flat so when a property description says go 500 feet, part of that might be up the side of a hill and not 500 feet in horizontal that simple math applied to a coordinate can come up with.

    Here is a link where you might get some hints on what markings to look for as you walk the property line, some might still be observable. https://www.nh.gov/osi/planning/programs/clsp/documents/map-compass-skills.pdf

    Like Boyd, if you need precision, if this potentially involves a legal issue, I would consult a surveyor.
  • privet01 231 Points
    edited November 2020
    Magnetic North is subject to east and west variation depending one where exactly you are. It also changes over the years. So if the bearings you are going by are not recent, then there are corrections that might need to be figured in to them.
  • I pointed out the link, https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#ushistoric, so I am familiar with what you are saying. I am just trying to figure out how to use the information on it, add to (I think (rather than subtract from)), the degrees\azimuth, the difference from 1993 to 2020? My lines go through woods, I am cleaning up, taking down dead trees (not big ones :)), do not want to bother someone elses property, does not need to be exact, don't expect to be exact, just reasonably close.

    Thinking about it, being that 2020 is 14 30' W, and that I do have some markers, that I do get close to (but not exact) using the compass, I think that they must have done it using magnetic north. If I were to add 14 degrees to the azumith that I have, for those close matches, it would be nowhere near the markers. There are other side lines that have no markers, that I am having trouble with.

    Above, it was noted that the difference from 1993 to 2020 is 1.47 degrees. So using the origional azumith of 6.45 and adding 1.47 to it, that brings it pretty close to 8.0 (7.92). Agree or disagree?

    Also, if you want to reverse direction, does the add or subtract changes?
  • "Above, it was noted that the difference from 1993 to 2020 is 1.47 degrees. So using the origional azumith of 6.45 and adding 1.47 to it, that brings it pretty close to 8.0 (7.92). Agree or disagree?"

    Since your declination is westerly, and it decreased by 1.47 degrees, then your magnetic heading would also be decreased by 1.47 degrees. If your 1993 magnetic heading was 6.45 degrees then for 2020 it should be about 5 (4.98) degrees.

    True North will not change.

    To reverse your direction when following your compass simply add, or subtract 180 degrees.

    You can get a MUCH more detailed instruction from Map Reading and Land Navigation, (Field Manual) FM 3-25.26 which can be downloaded. See pages 6-8 to 6-12. Yes, there was a time when people had to find their way around without GPS (or LORAN) in places without street signs. Some still have to know how.

    Here are two suggestions.

    1. If still in doubt, buy a can of spray paint and a six pack. Then invite your neighbor over to walk with you as you mark trees. Take the six pack so you don't get dehydrated, and offer to share with the neighbor.

    2. You could use your phone with a GPS app to record the location of survey markers you find. That GPS device only has to be accurate enough to lead you back to where you are close enough to spot the corresponding survey marker. Just be sure to pay attention to which format you are using when you write down the numbers. Lat Lon - degrees minutes seconds decimals / degrees minutes decimals / degrees decimals. Or, Military Grid Reference System (MGRS).
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