How accurate is the HMC5883L Compass?

I'm trying to survey a property line that is North 0 degrees 50 minutes East. I can't read 50 minutes on my hand-held compass.

Can the HMC5883L Compass module read that precise?

If not, are there any other compass modules that can read that precise?

Thanks.

To check the accuracy and other characteristics of components. Check the datasheet. Always check datasheets. Get used to this practice when dealing with electronics. HMC5883L datasheet

Rent a transit - rental places should have them

Can the HMC5883L Compass module read that precise?

No, and it must be very carefully calibrated to achieve even +/- 2 degree accuracy.

jremington:
No, and it must be very carefully calibrated to achieve even +/- 2 degree accuracy.

Thank you very much.

I just went out and did it manually with a “hand-held” compass. 50 minutes is close enough to 1 degree and my compass has a very fine 360 degree marks. So I just went with reading 361 degrees. The corner posts have already been put in place by a professional surveyor. I’m just trying to mark a straight border line between the corners. Over a hill and through dense woods. Can’t see the corners from each other.

Anyway, I must have done pretty good because I came out within 5 feet of the corner marker. I was using a tripod this time and being extremely careful with my readings and measurements. The last time I did it I tried doing it by hand without the tripod and by the time I got to the corner post I was 30 feet off. This time being only 5 feet off feels much better.

My hand-held compass must be pretty accurate.

+/- 2 degrees wouldn’t be any better. Maybe even worse. So I may as well go with the manual compass. I’m happy with the line I just marked out.

Have a google about basic surveying . With several markers you can construct lines of sight across hills , triangulate and so on .
Mason/Dixon went across the USA using such methods .

Or rent an instrument .. if your cheapo device shows there to be a difference compared to the professional who will they say is right ?

You also have to allow for the difference between magnetic north and true north which varies from place to place and varies slowly over the years.

For example, according to my Ordnance Survey map for the Peak District in the UK magnetic North was about 2°40' west in July 2011 and changes eastwards by about 09' each year.

...R

Robin2:
For example, according to my Ordnance Survey map for the Peak District in the UK magnetic North was about 2°40' west in July 2011 and changes eastwards by about 09' each year.

When I first started walking the hills of the Brecon Beacons, we were using 8 degrees declination. These days its about 1.5 degrees.

Thanks for all the feedback.

What I'm doing is not real critical. As I say, the corner posts have all been set by a professional surveyor so those are basically carved in stone so-to-speak. At least from a legal perspective. The cosmos itself may be changing, but I don't think that will change people's property markers.

Just for further information, for whatever it's worth.

I own 10 acres of land. Fortunately it was surveyed many years ago and all the corner posts are well established. However the lines between the corner posts have not been well-marked. In some situations the corner posts can be seen from each other so a direct line-of-sight is possible to establish those boundaries perfectly. In other places a line-of-sight cannot be established because of hills and dense forest.

Why am I concerned with marking out these boundary lines?

Well, recently two people bought property next to me. In one case the follow actually came onto my land by a major distance (i.e. he was 1/3 of the distance into my property) and he was putting up posted signs on my property. I had to go out and show him where the corner posts are. Fortunately once I showed him the surveyor's stakes he was quick to recognize and respect the true boundary. And in that case a line-of-sight was possible between the corner posts. So now we have that entire line marked off very clearly.

The gentleman was very good about it and didn't give me any strife. But, as I say, originally he was 1/3 of the way into my property putting up posted signs thinking that was his property line. So had I not said anything right away, that could have become a property line dispute at some point in the future.

That was on the back property line from my house. He was originally 1/3 of the way into my back yard. So I'm glad I was able to nip that in the bud and clear that up in a timely manner.

Shortly after that my next-door neighbor to my right died. His place is now up for sale. So I'm marking that boundary really well now so when the new owners move in there won't be any confusion over where the property line is. That property line is also line-of-sight between corners so again, no major problems there.

However, most of my property is on the other side of the road. And that's where the property lines are murky save for the corner posts. I've decided to take preemptive steps to mark these lines clearly before any new neighbors move in. And so that's where I wanted to mark the boundary lines as close as possible to their correct location. I don't mind being a few feet off one way or the other. Even the deed states +/- a few feet. But I don't want to 30 feet off, like I was the first time I tried to mark it.

I finally got it down to where I'm only 5 feet off at the very end of the line. I can live with that.

I was thinking that if an Arduino electronic compass could be used to mark out a perfect line I'd build one.

But if the electronic compass is only good to +/- 2 degrees, then I'm already doing better than that with my hand-held compass. So not point in building an electronic compass that won't even do as good.

I also thought I'd post this here because sometimes electronic makers come up with ingenious ways to improve the accuracy of various sensors. I've seen this done with distance senors on robots where by using more sensors and configuring them in certain ways accuracy can be improve over what a singe sensor can provide. I was thinking that maybe someone figured out a way to squeak out better performance from a compass sensor too.

Maybe by using several of them and calibrating out their mutual errors with a known measurement? Makers are always coming up with ingenious ways of solving these sorts of problems.

Fortunately I've already solved my problem. Simply by using a tripod to hold the compass steady and taking great care in reading the dial accurately I was able to mark off the line with only a 5 foot error over 565 feet. That's close enough for me.

I've often wondered how the electricity utilities align their pylons. I many (most?) cases a person standing at the location of the base of one pylon could not see a person standing at the prospective base of the next pylon yet over long distances they seem to have been able to locate the pylons in an incredibly straight line - my guess is that any error is a matter of inches rather than feet. And this was done long before GPS.

Presumably it was all done by triangulation, and I wonder if that is an option for you. In essence it would mean erecting an additional marker post at a location where it is visible to at least 2 other posts. This would probably not be on your boundary line and might even be outside your property as it is just a temporary thing. Then use that new post to site another new marker etc etc.

I guess the essential tool is a theodolite for measuring angles between marker posts.

Back in the days of the British Empire the Ordnance Survey surveyed India using surveying chains and theodolites with sufficient accuracy to detect an error caused by the gravity of the Himalayas pulling a plumb-line off vertical (when they did not know the Himalayas existed).

...R

Robin2:
Presumably it was all done by triangulation, and I wonder if that is an option for you. In essence it would mean erecting an additional marker post at a location where it is visible to at least 2 other posts.

Unfortunately there is no position where both corner posts can be seen simultaneously. Although there might be a possibility of that if I were to extend the corner post to an extreme vertical height. Perhaps by using a tethered helium balloon?

Speaking of GPS, and more specifically Google Maps:

When I decided to remark my property lines I couldn't find one of the corner posts. I had an idea of where it should be, but searching for the actual post failed. So I actually came back in the house and looked at a Google map of my property. The clarity is astounding. Of course, you could never see a surveyor's stake. But what I was able to do was to use the Google map to measure back to where the stake should be. Then I was able to study the Google map in detail at that area. I noticed a configuration among the trees that I felt I could recognize on the ground. So I went back and looked again taking note of configuration of the forest trees and low and behold I found the stake right where it's supposed to be!

It was actually hidden by a large dead branch that had fallen on it.

So that was amazing that I was able to use Google maps to find my property stake. But it actually worked. Now I have four foot tall 2" diameter pieces of iron pipe painted bright yellow for the corners. I'll never lose them again.

Robo_Pi:
Unfortunately there is no position where both corner posts can be seen simultaneously.

I suspect you are referring to the two corner posts for the boundary line that you are having difficulty with. But I was thinking of working from one of those posts and the posts on the other boundary lines so as to create an intermediate post (maybe you will need a few intermediate posts) that can be seen from the corners of the difficult boundary line.

Or, ask yourself another question, how did the professional surveyor do it?

…R