This may venture into IMHO, but since I have some specific questions I thought I’d try here first.
My husband and I are buying 40 acres of land in a couple of months, and we were thinking of getting a GPS device to help in determining where we should put the road in.
It’s wooded land with no real landmarks, but the road needs to divide it up pretty evenly, but also be cost effective. Since the land is kind of hilly, it would be helpful to be able to see where we are on the lot while we are walking it, instead of just guessing.
So, my questions are:
The land is wooded. Is tree cover going to be a problem with getting the device to work?
From the looking around I’ve done, it sounds like the loaded maps cover “most” of the US. Can I look online somewhere to find out if the area we need is covered adequately by the included maps, or do I have to just buy the unit and hope? (I’ll have to buy on-line.) The area is semi-rural, but close to Little Rock.
We might be interested in doing some geocaching over here, all though it isn’t the primary purpose of getting the unit. Does anyone know if some units offer maps of Japan?
I’d like to keep the cost under $300, but as low as we can get away with. It will probably be used very rarely.
Just how accurate are the things, anyway? If it can’t show us within 30 feet or so of our exact location, it’s not going to do us much good.
Not used it in the circs you suggest (only in car and on the ocean), but quite a few of your questions can be answered by the manufacturer and/or agent. Maybe ‘should’ be answered that way as they’ll be the people you’ll take it back to if it doesn’t do the job you want.
I would think the path of a road in a hilly area is largely dertermined by the topography - otherwise you’re moving masses of earth at huge cost.
GPS can be very accurate now, say 5-10 feet, but like I say, this might be better to consider the way the land lays.
Depends how densely wooded it is. Most consumer GPS units have pretty good antennae nowadays, but dense woodland can still produce spurious readings. If it’s raining, you can often forget about getting a good lock, or even any signal at all, as wet leaves do a very good job of blocking the satellite signals.
I’m not quite sure why this is relevant to what you want to do. Most GPS units only come with street mapping installed, which is not going to be much use in an undeveloped plot. You can buy some which have topo mapping available, but you usually have to buy the relevant sections of mapping and install them via an SD card or similar.
If you are trying to lay out a road, I imagine that what you would want to do is find the co-ordinates of the corners of the plot, then calculate the suitable co-ordinates for points along the road and use the GPS to find them on the ground. Either that or walk a possible route of the road, with the tracklog on, and compare the tracklog to a map on the PC (there are plenty of programs that can do this).
Again, I’m not sure why you would need the maps. Geocaching uses lat/long co-ordinates, which are valid on any GPS unit (as long as you have the correct datum). But yes, most units above enty-level let you install different maps, so you could get street mapping for Japan. As for topo map availability, I am not sure.
$300 should get you a pretty decent unit. You probably wouldn’t get all the bells and whistles for that price (I don’t know how prices compare to the UK, but over here, that’s about £160 or so, and entry-level units start at around half that.)
With good satellite coverage, you can often get accuracy down to around 15 feet or less. Under dense tree cover, it is likely to be less accurate. One thing to beware of is that you must make sure that the GPS unit is set to show the correct map datum, otherwise your lat/long will be out by a considerable distance. (The datum is basically related to the baseline used by the cartographers - a map drawn in the UK will use the UK Ordnance Survey datum, a map in Arkansas will use the US datum called NAD27. If you extended the UK datum right out towards the USA, you’d find that the lines of latitude and longitude are in a slightly different place from the USA datum. The GPS standard is called WGS84 and is a kind of global best fit of all these different datums. Most GPS units can adjust between the various datums and show your lat/long adjusted to fit the map.
I have heard good things about the Garmin eTrex range. The basic unit is here: http://www.garmin.com/products/etrex/ but follow the links at the right for more expensive units, with mapping etc. The eTrex Vista retails around $200 in the US I believe.
The Garmin Map Source topo maps and worlkd street mapping will work with the Vista.
The standard data set that comes with it is not very good. The additional streets dataset is great.
The topo data set has a contour interval of 1:100’ which is not very useful.
I also have 40 acres of land, and only about half of it is wooded, and it’s not dense wood at all. I sort of wonder how a GPS would help you put in a drive. You say the land is hilly, yet the road has to divide it up pretty evenly.
Why does it need to be divided?
If you are planning on subdividing it, you need a surveyor, no question. Otherwise, especially on hilly property the drive goes in where it makes the most sense for travel
I guess you could find your property corners and mark them as way points…. Then walk where you want the drive to be. I’m still a little confused as to why you would need to do this though.
Colophon, thanks. I’ve never used one of these things before, so bear with me. If I go to the lot and find the four corners, I can mark them on my GPS device, right? Then it will show me where I am in relation to those four corners? That’s really all I need it to do, I guess. I know where the land is, and the corners will be marked, so that should do it. I just need to get an idea of how steep certain parts of the land are so that I can determine the basic best route for the road.
Yes, that’ll work for orienting yourself roughly on the property. If you have a topo map on your PC, you should be able to connect the GPS to your PC and download the waypoints and track log onto the map, so you can see exactly where you’ve been. There are various cheap or free programs that allow you to do this.
Plus, of course, you can set a waypoint at any particular spot, so that you can find it again. So if you find a spot where you want the road to curve, or where you discover buried Indian treasure, say, then you can store it in the GPS and go back to it when you want.
You mentioned four corners. If the land is square, that’s 1320 feet per side.
A square mile is 640 acres. 5280 feet per side. That’s called a Section. A quarter section is 2640 feet per side or 160 acres. A quarter/quarter is 40 acres.
I see that your location is Okinawa, but I am guessing that if it is square, and at 40 acres, that the land is in the US? If that land is in the US, and it’s square, it was almost certainly divided up and described by the PLSS.
Thanks, guys. Enipla, that link is helpful (the land is in Arkansas).
The reason we need to do this is that we’re dividing it into 5 acre lots and when the survey company comes out they’re going to want to know how we want it divided and where we want the road easement. There are several different ways to do this, and it’s hard just wandering around out there hoping you’re where you think you are. We also may keep some of the land, and it would be useful to know where we were on the lot when we saw the part we liked.
More: Some GPS handhelds can do “waypoint averaging” and get more accurate positions by measuring for seconds or minutes or hours in the same spot. I do this for amateur surveying applications and get standard deviations of 18 inches (not feet) with half hour averages under a clear sky. It’s harder in the woods but waiting still gets better accuracy. Foliage seems to make it more difficult so winter’s a bit better. If you want to get USGS quadrangle maps, beware - latitude and longitude are defined by “datums” (the plural of “datum” in this specific context) and many of those maps use the older NAD27 datum, which is tens of feet different than the WGS84 or similar NAD83 datums typical of GPS units.
I forgot to point out the Garmin GPS-60. I have 4 of these and use them for the surveying. They feature 12 channels (and I often see 9 or 10 operating), waypoint averaging, a quad helix antenna, and a price in the mid 100’s.