Well, sort of, actually 0.98m in NATO where the approximation of Pi =
3.2 is used giving 6400 mils in a circle compared with 6283 milliradiansOne mil is approximately 0.06 of a degree and a variation of 1 mil is impossible to determine using any field magnetic compass.
Oops. I managed to get my scale wrong again, possibly due to my compass being graduated from 0 - 64, not 0 - 6400.
That would depend where you were coming from. The military version is
1/6400 of a full circle which is marginally different.
The unit used was the Mud (abbreviated m to distinguish it from the metre which is abbreviated m), this is the distance of the impression left on a floor made to BS66754 at 23degC by a surveyors left boot whilst walking at 2 MPH.
The Mud is exactly 12 inches in length.
Roger Chapman ( snipped-for-privacy@nospam.zetnet.co.uk) wibbled on Wednesday 26 January
2011 15:41:
Sorry I think I missed a step (was along time ago). I guess I must have used 2 points, the zero and another one that was in sight of both the zero point and the next station point - a reasonable distance apart. I'll have to read the Leica manual to remind myself - they basically told you how to do it...
But I guess I must have calibrated the new station point to two orevious points.
Same way, with less accuracy - you get abearing to the said landmark from the map.
ITYM 304.8mm
Basic Triangulation. The points you survey need to join up in /triangles/. If you join a series of points in a daisy chain your errors could in theory at least cancel each other out and you would have 0,0,0 when you get back to the first point yet still have errors in the intermediate steps. Establish triangles between the points and the errors will be apparent. Establishing a position in the absolute rather than relative sense is also a matter of triangulation, or you trust the position of the official survey's benchmark/trig point
The crux of the matter is that in order to position your survey on the map you need to know what passes for the absolute position of at least two points.
Which brings me back to square one or at least somewhere round a circle. Taking a bearing from a map is likely to be even less accurate than using a sighting compass which in turn is unlikely to give better than half degree accuracy. Disregarding my scale error in my earlier misuse of mils that is a possible displacement of circa 9 yards at 1000 yards distance.
Roger Chapman ( snipped-for-privacy@nospam.zetnet.co.uk) wibbled on Wednesday 26 January
2011 18:21:
I will have to say again:
does reference to map based coordinates matter? - and this is something for the OP...
I could survey our end of the road with no knowledge of longitude, latitude or which way north is.
I would have a plan accurate to cm with all the houses and boundaries accurately positioned relative to one another and all distances would be correct to the margin of error.
If the object of the exercise is to interpret a district planning scale map, draw some conclusions from it and then make some marks on the ground, then an external frame of reference is not essential.
It is generally easier with such maps to take surveys of points that interpret cleanly to the map, such as other people's boundarys and any landmarks and "fit yourself in".
eg - my deeds (original ones) say I have specifically a 75 x 100 foot curtilage.
The scale isn't great and the lines are thick and fuzzy.
I know I am a corner plot, and I know where the pavement is - my boundary might be the tarmac edge or it might be a foot or so in.
One of my neighbours built a boundary stub wall that defined a short edge of his boundary with me.
Long and short is the map is not good enough to say "this is my land" to the foot but I can make a 100' x 75' plot fit in cleanly to my neighbour's wall, to my other neighbour's fence and be a bit back from the pavement - so noone is complaining...
I suspect that is the way to proceed in a great many cases. If the OP has a plot in the middle of nowhere with no adjoining bondarys or the deeds actually mark coordinate points in numbers, then, I agree, it becomes more important to fit to the OS coordinates (whatever the local system is).
In which case, the best you can do is triangulate off as many distinct landmarks as possible, even distant ones[1] and use the best maps available of your area including, of course, the one taken as a definative layout of his land.
[1] A total station can of course be used as a theodolite (ie without the ranging) so sighting a mountaintop over there, a building 1/2 mile the other way and so on should get you about as good as is possible without conducting a series of medium distance surveys over several miles in stages from known markers (ie like map making used to be done).
I was able to stand under a tree, get readings to 5 decimal places of a degree, feed those readings into Google Maps and get a picture of the same tree. That's certainly close enough to find boundary pegs. I was able to stand at each boundary peg, take the readings and plot them on a diagram and get a picture rather like the plan of my section supplied to me by the authorities.
Maybe that is the problem. They just left the Theodolite at one point in the middle of the section. They may have moved it a couple of times, but I watched them putting three pegs in without moving the Theodolite. The land is so steep and overgrown that one peg cannot be seen from the next peg. In addition I prefer to use abseilimg gear while climbing around on the slopes of around 60 degrees.
I don't see how there can be any kind of checking if they don't move the Theodolite to each peg.
The last survey in 2006 was done by someone who is on the list of people approved to do that work. And I trust that survey because it makes sense. The front fences of all our properties are now in a straight line. The pegs that I am able to measure are within about
10mm of the correct figure.
I think we are all at a disadvantage here as none of us know anything about NZ mapping habits. Matty refers to a section of land which may or may not have anything like the same meaning as it has in the States or Canada where it is an area of one square mile.
Yes indeed but by including features that are undoubtedly already positioned on maps of the area you are linking your survey to a map on which direction has been established.
The external frame of reference is already there. Whatever Matty has it will be a subsection of a larger area whose boundaries are certainly already mapped. Getting the subdivisions in the wrong place will mean someone's holding is larger than it should be and someone else's is smaller than it should be. However unless the land is extremely valuable and the dimensions critical for access or building then even a 500mm discrepancy shouldn't be enough to get any land owner losing sleep over it.
And on a modern housing estate all your neighbours will have similarly defined plots which, when added together, should match the area of the original development. By contrast Matty and his neighbours appears to have plots of known size but without all the boundaries being clearly defined.
You sure that wasn't 6 decimal places. By my admittedly suspect calculations 5 decimal places gives a resolution in longitude of approximately 37 feet which is 10 times worse that a 10 figure grid reference in the UK.
Regardless of the resolution hand held GPSs do not usually have accuracy anywhere near as good as the resolution would imply. If there is such a model on the market I would very much like to buy one so what is it you are using.
Being able to get a fix under tree cover is also a useful aspect which my GPS sadly lacks.
A section in NZ is just a piece of land that could be from say 600 square metres upwards. My land was first surveyed 160 years ago, and some of the fence posts and barbed wire are still there and roughly in the right place.
The land here is valued at about 500 GPB per square metre. That sounds a lot to me.
There are plenty of accurately known points all around. I could measure all of my pegs myself if the land were flat. But parts of the land are extremely steep and overgrown and most of the time one boundary peg cannot be seen from the next.
I presume that your deeds, like Tim's, specify the extent of the land. Nevertheless if it was in the UK the chances are after all that time what was left of the fences would define the property rather than the nominal area.
It sounds a lot to me as well. I thought from the description it was low quality agricultural land which can go for as little as £5K a hectare round here. £5M per hectare is good quality building land in the UK. On that basis Tim's plot would be worth some £350,000, more than double the average cost of a home in the UK.
These days UK land measurement is generally plan view only. Is your land measured on the map or on the ground?
Roger Chapman ( snipped-for-privacy@nospam.zetnet.co.uk) wibbled on Wednesday 26 January
2011 20:31:
That's the point I've been trying to make ;->
Mine's not modern (deeds, and in feet!) - in fact rather the opposite problem is that everything's rather fudged and random. I have a lump in my boundary that is alluded to on the plan but does not look anything like the shape it actually is. Nothing we can do except accept it as established fact
- but noone is whining... I'm lucky that my principle dimensions are actually stated so categorically and actually fit in the space available.
I can imagine. Which was my other point: if Matty can "fit" his plot between his neighbours such that neither complain, everyone's happy - and a careful DIY survey can accurately establish a plot of a given size. That only leaves the matter of minor translation and rotation.
What I would do if I had an instrument on day hire, is set corner posts to exactly the plot size and fitted as seems reasonable.
If there is a bit of hooha about whether it is a few metres to far to the right or the left it is now very easy to put a second set of pegs in by tape measure alone until general agreement is reached. At least Matty will know he has the right land area - even if he has to move it about a bit until eveyone else thinks they have their areas. He could even do a quick survey of their land to establish their exact areas too. Cheers
Tim
My property is bounded by 7 straight lines and there are only two boundary pegs that can be seen from each other. I managed to mark the fenceline along the longest side by suspending a hose from the top of the cliff to the peg at the bottom, and using a plumbob in a few places. The hose followed the contour of the ground rather well, i.e. a catenary curve. How do I measure along that and adjust to get the horizontal length?
I think you're out by a factor of 10 - I make it 44" exactly at the Equator [1]. At this latitude (say 51N) that will of course be reduced by cos 51, IOW to about 28".
I've no idea how this affects the discussion you're having.
[1] Assuming earth circumference of 25k miles.
The Land Registry maps are certainly interpreted with surprising accuracy. A year or two ago I had a letter from the Land Registry, they systematically review their records and check for accuracy and discrepancies. They had found an error on the map for my property and the adjoining council owned playground so that the boundaries overlapped. The difference being the original boundary of the 19th century garden wall and the modern chain link fence. As the 4 inch gap between the two is not of much interest to anyone we decided not to spend money on lawyers and surveyors to tidy things up. At some point, should the freehold ever change hands, the matter will no doubt arise, at which case the costs will be just another part of the conveyancing.
In surveying boundaries, a map will show features that are (or were) on the ground, the surveyor is taking measurements with reference to those features.
For OS maps see <
I worked it out assuming that the distance form me to you is 20,000 km and divided by 180 degrees!
I have a Tom Tom XL250 navigation unit. When I ignore its planned route and turn off the motorway, it recalulates a new route in a few seconds. I think it knows when I change lanes, i.e. a resolution of a metre or so. I can walk along my footpath and the last decimal place changes.
I've had a problem with it for surveying becuase sometimes it suddenly decides that I am too far from a road, so it gives me the lat/long of the middle of the nearest rioad. It doesn't have a "walking mode" so I can't turn the unwanted "middle of road" feature off.
I must admit that I was thinking of modern in terms of after Britain had been surveyed and accurate maps were to be had.
My neighbour is a farmer and I am absolutely certain that he has a boundary that diverges from the line on the map by some 3 metres at one point. It is however a particularly grotty bank of a gully on a north facing piece of steep hillside that wouldn't be worth arguing about if the other owner wanted to do something about it. Indeed it might be worth moving the fence to the top of the bank next time it needs replacing.
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