An interesting case study in measuring one's own land.

I have a former working background in surveying calcs and mapping, and have also been long considering embarking upon a similar DIY project for my own property.

One aspect I note, having spent quite some time at it myself, is that there is somewhat of an art to the generation of accurate topographical contour lines from a set of manually surveyed points. Both in what points to survey, and in how to treat the points. The reference term here is TIN or Triangulated Irregular Network. Automated software does a fair job of building TINs, but the resulting contour lines can in some areas represent detail or features that don't really exist.

For example in the author's contour maps under the "Finally, The Mapping" section, much of the leftmost half is particularly sparse in measured points and as a result, the contour lines have interpolated some wacky humps-and-hollows across that half of the land, at least some of which probably don't exist in reality. (Technically speaking, long skinny triangles = not ideal, particularly at large scale; and separately, another key word or concept to look into is that of topographical "breaklines")

Ultimately, the specific arrangement of triangles in the TIN defines how the contour lines will be drawn. Good starting data is half the equation, and the other half is how you TIN it.

Database connection error - could not find the article on archive.is or archive.org but it was available on Google Cache:

https://webcache.googleusercontent.com/search?q=cache%3Ahttp...

Great writeup, may add to my list of projects for 2024.

I am halfway done reading, "GPS and GNSS for Land Surveyors Fidth Edition", which I bought to better understand the survey issues we were having with surveys and data on a project I was on in Saudi Arabia for 6 months last year and 2 months this year. I was a physics major and I have to say surveying is a lot more complicated than I had ever imagined. Realizing that relative height data from one point to the next is straightforward, but that a simple elevation reading is based on MSL and what area in the world you're in for your reference are just a few of the variables that go into the craft of surveying. I really went down the rabbit hole, but I've learned so much and I am now hooked on taking it much further.

In my high school in 1980, we took a 2-hour survey/questionnaire filling in circles with a #2 pencil, and we we waited 3 to 4 weeks to get the results of what career we were suited for, and mine was cartographer! I imagine there were humans and machines doing the analysis back then, but maybe I should have followed that path!

Another good source for RTK receiver stuff could be https://www.ardusimple.com/

I was once going through the same process and considered buying from them. But then a more official survey turned out to be rather cheap so I did not have any need any more.

https://bendauphinee.com/writing/ Link to the post

It's an interesting technical challenge. I wonder if there is any "tangible" benefit by moving your land these few meters and spending $4600 on a surveyor to do it considering it's a woodland property. One immediate benefit I can see is that it now borders a road and previously it didn't. That's prety useful.

What are the laws in that place? Could you, let's say, not do any surveying, build a fence, and then have a new neighbour show up 25 years later with a survey and ask you to move it?

Here, we have this law that if you occupy some piece of land for 20 years (with no "malice", if it can be proved you knew it wasn't your land the amount of time is 30 years). After that time it essentially "becomes yours". The neighbour had no fence, but I imagine he could argue his camper being there for the required amount of time fulfills the requirement and then I imagine the boundary would get redrawn.

What is the authoritative thing that defines the boundary in absence of pins/markers?

2 things:

first, absolutely fascinating topic, and solid write up. i skimmed through certain bits but am wondering: "Turns out, the survey was off a lot more than any of us expected" did you mean off from the title, or the surveyor's work? (also, since you're in Canada, allow me to quote Les Stroud: "if you sweat, then you die" sweating is actually the easiest way to get cold heh, you brought sweat up in the same paragraph)

second, i'm a musician who lives in Anchorage. i'm a recovering programmer. a good friend of mine is a recovering surveyor, and he runs Trapper Creek music festival up here, 15 years and counting. since you said you mounted equipment on a mic stand you just happened to have -- wondering if that event you were planning for was music related :-D

This was wonderful!

Do you have more posts about how you went about buying the land?

The surveying aspect is super interesting, including the fact that your neighbor had such an imprecise knowledge of their boundaries.

I wonder what the history of surveying looks like... I assume as mapping precision increased there must have been many many cases where structures were found to lie on neighboring properties.

This is an awesome project. Curious how much we could "cloud" apply NTRIP RTK corrections over 5G to any mobile phone device. It wouldn't be survey quality but it seems like it would work well enough for many use cases.

I wonder what the gain is in doing this compared to using government lidar data - it seems this is available for new brunswick [0]

The 0 cost solution would be to use this lidar data for topography, perhaps even for tree clusters, then use an aerial photo to help plot on some extras like roads. Maybe there's a little accuracy difference I'm not sure

[0] https://open.canada.ca/data/en/dataset/80ccc975-d6ec-9e24-a7...

A really nice write up! I’m a professional land surveyor and it was interesting reading an outsiders perspective; for the most part you really nailed it!

I'm curious if you looked into PPK and possibly hiring someone with a drone based LIDAR setup to give you a quick DEM.

I actually prefer PPK over RTK for all work these days. RTK still gets used, but only to help control the drone's flight path in specific scenarios. Otherwise, uncorrected flight paths are fine since all the collected data is run through PPK after collection.

A good write up! The one thing I’ll add is that in most regions that aren’t terribly remote, you can just use a VRS RTK service, avoiding the entire base station effort. You’ll still get 1cm RMSE, and all you need is a temporary subscription and a cell modem, often built into your receiver.

Hi Ben! Cool seeing you on HN!

so incredibly cool

Google has held a couple of GPS precision challenges for smartphones, and Galileo recently launched their High Accuracy Service (HAS) for high accuracy Precise Point Positioning. Android has built in support for full GNSS phase measurements. Smartphone positional accuracy is already pretty good with L1+L5 bands, and it will probably get even better soon.

https://www.kaggle.com/competitions/smartphone-decimeter-202...

https://www.euspa.europa.eu/european-space/galileo/services/...

https://barbeau.medium.com/gnss-interrupted-the-hidden-andro...

Right now, the GPS receivers that support RTK corrections charge a substantial premium for the capability, so you're unlikely to see this in a mobile phone without the phone makers intending it.

Also, you only get ~3cm precision while you have direct line of sight to a reasonable number of satellites, including some that are closer to the horizon. So if you're close to a building, or in a car with a metal roof - the accuracy might not turn out that great anyway.

People doing fancy surveys use a special antenna that rejects reflections from near ground level, but has to be pointed towards the sky. That's undesirable for a phone, where the user might want it in portrait or landscape, might hold it at an angle for readability, and so on. I have no idea if you could achieve respectable RTK performance with an omnidirectional antenna.

So even if you were the iPhone GPS chip selector, and you had the market leverage to get RTK support cheaply and get a killer deal on network NTRIP corrections, you might think the benefits aren't worth it.

I suspect costs will fall precipitously in the next few decades, though, because this sort of tech is useful for self-driving cars, and automotive order volumes tend to make chip prices fall a great deal.

You'd have to have a GPS capable of taking the correction data, which a lot of units can't. I'd be interested if the iPhone could, since it has L1+L5 capacity, but I'd bet not, and iOS doesn't expose their location data very well anyway (a lot of mapping seems more flexible on Android for this reason).

Should perhaps start with universal SBAS support first, which seems to be not a given still.

OTOH at least in Europe there’s the EUPOS project that, if opened to the public, could very well provide good-enough corrections to give everybody high quality results.