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Measuring Land

Started by WH_Conley, February 01, 2005, 10:29:50 PM

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jeffreythree

If you can find the property on Google Maps, then the Planimeter works pretty well: http://www.acme.com/planimeter/ .  Just put way points wherever the property line changes directions.  View as a satellite, topo, or usgs doq image.
Trying to get out of DFW, the land of the $30,000 millionaires.  Look it up.

redprospector

I'm lacking a little in the math department, so I got a Garmin Etrex GPS. It has an area calculator built in. Just set it to area calc. and walk around the area in question. It's pretty accurate and is right with the State Forestry's $4000.00 GPS.
It dosen't work as well on cloudy / rainy day's.

Andy
1996 Timber King B-20 with 14' extension, Morgan Mini Scragg Mill, Fastline Band Scragg Mill (project), 1973 JD 440-b skidder, 2008 Bobcat T-320 with buckets, grapple, auger, Tushogg mulching head, etc., 2006 Fecon FTX-90L with Bull Hog 74SS head, 1994 Vermeer 1250 BC Chipper. A bunch of chainsaws.

mad murdock

According to my 'learnin' 60 seconds to a minute, 60 minutes to a degree and one degree = one nautical mile, this is true for N-S lines(lattitude), E-W (Longitued) degress will equal 1 degree per nautical mile along the equator, but he further North or South you go from there, the closer the degree marks get, for obvious reasons.  1 Nautical mile equals 1.15 miles or about 6,072 feet.  so if you divide according to the avobe information, one minute = about 101.2 feet, one second will = about 1.6 feet.
To figure acres within a polygon, you would have to know the 3-D lay of the ground, I am not a Surveyor, but have done lots of work following Survey parties around in Alaska, as a member of their helicopter support crew, and from what I have been able to glean, survey only concerns itself with the 2-D area of any given Polygon, i.e. if you have a square mile (640 acres), you follow a line 1 mi. on all 4 sides, and if you were to divide that area into say 2 acre parcels, you could come up with 15 to 20% more acres on the small survey than on the large one, just because you are not walking every contour of the land in between the mile long sides, so you always come up with some "bonus" acres whenever you take a large parcel and cut it down to small bits- at least that is the way I have found to visualize it.. wokrs for me, I hope its a bit clearer than mud:-)
Turbosawmill M6 (now M8) Warrior Ultra liteweight, Granberg Alaskan III, lots of saws-gas powered and human powered :D

Scotswood

Go metric.

Use grid ref (10m points) instead of lat/long - you can probably use an on line converter as each point is unique. Another way could be to convert minutes/seconds of angle to metres and do it that way.

Then calculate hectares 100mx100m, then convert that to acres, again using an on line converter.

I know we invented the imperial system, but it's easier to count in 10s!.

BaldBob

Madmurdock,
All legal land surveys are in 2D, even those for 2 acre parcels. While there may be a "bonus" in surface area when there is topographic relief, there is no "bonus" in acreage.

SwampDonkey

Quote from: BaldBob on May 14, 2009, 03:08:33 PM
Madmurdock,
All legal land surveys are in 2D, even those for 2 acre parcels. While there may be a "bonus" in surface area when there is topographic relief, there is no "bonus" in acreage.

Ditto, to Bob's post. Surveying is on horizontal distance, not slope distance and thus not surface area of the landform. And as far as bonus, there is no extra trees on a plot with a big dip than there is with a plot that is flat. Trees grow toward the sun, not perpendicular to the land surface. Otherwise the woods would look like a pin cushion. When you GPS a plot you can get 3D relief because z-valued are collected, but the area and perimeter are 2D (perimeter is also computed for slope distance).



Circled in yellow.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

mad murdock

I am no surveyor, as I stated. I have been puzzled though, that whenever we apply herbicides on commercial forest land here in the west, (ORE, WASH, IDAHO, N. CALIF), almost without exception, when the customer supplies their .shp file (polygon), for us to use in the helicopter, and we fly the area, the acreages do not match exactly, almost every time the area sprayed differs form sometimes up to 5-7 percent from the area that the customer supplies drawn from their GIS dept, or walked on the ground with a plugger.  The ground we cover is very vertical, usually greater than 20% slopes.  Thoughts??
Turbosawmill M6 (now M8) Warrior Ultra liteweight, Granberg Alaskan III, lots of saws-gas powered and human powered :D

SwampDonkey

A lot of agencies are using consumer grade GPS with a lot of multipath that they are not base correcting. All my GPS traverses have to be corrected from my GEOXM in order to be accepted by the NB forestry companies. But, a GPS with capability to average positions at each vertex will have almost no need for corrections. This is possible with my GEOXM and ArcPad from ESRI. To do base corrections I need GPS Correct from Trimble for the TSIP protocol (Arcpad extension) and an internet connection to a base correction site, in my case I use Acadia Timber in Edmundston, NB. I could also use a base at Caribou, Maine but it is an unreliable site. Also, the capability to filter out non 3D positions, high PDOP and minimum elevation above the horizon for useful satellites (usually set to 15°) will help accuracy. I have distortion free aerials and all my traverses line up, whizz bang, with any roads and cut boundaries I see on the corresponding aerial. 3-5% discrepancy is acceptable, an 8% difference or more is subject to scrutiny, but that only pertains to my situation as the local standards may vary by region.

If the so called survey ends up with more acreage by adding up smaller parcels inside the limits then they did not do slope correction or the surveys have gross errors. Tree thinners think they should be paid on surface area, the standard established a long time ago is slope corrected distances. That argument comes up every season. For the slopes and areas we are working on it wouldn't add up to anything significant. I had a guy last summer question it and he took out his string box to prove himself wrong. I been around long enough to know when a guy is working and when he's pull'n a fast one. ;D

Horizontal = COS (θ) x Slope Distance

θ = ArcTAN (Slope %) using a % SUUNTO clinometer
                   100
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

BaldBob

mad murdock,

How are you determining the acreage sprayed?  You may be determining the slope surface area, which, as swamp donkey pointed out, is of no meaning in determining the acreage to be sprayed area since plants grow vertically - not perpendicular to the land. This is quite likely what is occurring, since spray choppers tend to fly at a fixed height above the land the land rather than at a fixed altitude.

BaldBob

Swamp Donkey,
I can see a case for paying more for thinning on steep ground - not paying for more acres (surface vs. slope corrected), but paying more per acre simply because of the greater difficulty in getting around.

SwampDonkey

Yes in that case, you are correct. The rates are based on density and difficulty. If you want to eliminate all the head ache just pay a good rate and take the good ground with the bad. ;) We don't work on over 35 % slope, 99 % of work areas are less than 20 % slope. I like some slope, trees tip real good and come to the ground with no effort. ;D We start a block tomorrow at 6:00 am, can't wait to start mow'n them down and listen to all the blat'n. ;) :D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

pappy19

I have used Deed Plotter and Topofusion, both are some of the best in acre calculations based upon known bearing and distances for use in Deed Plotter, and one can get estimated bearing/distances by using Topofusion; which will also give you Lat/Long as well. These are the 2 best programs that I have used in the land management work that have have done.

Pap
2008 F-250 V-10
2007 Lincoln LT
1996 Ford Bronco
Kubota 900 RTV
Shindiawa fan

SwampDonkey

I've used Deed Plotter as well for string box and compass traverse. Very easy to use and you can also export DXF to bring into a GIS program. I never went that way however because you needed a starting lat/long position or your map was at 0,0 on the globe. Our traverses never started at a known position such as a corner, they were out in the middle of a woodlot, even though most hit the marked property boundary. Best you could do was guess from photos and orthophoto maps. Many times the contractor never even knew where he was. A certain timber company got some free thinning. ::) By the time we had GIS we also had Trimble GEO3 GPS's within a couple years.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

pappy19

That's why you could use Topofusion and get within 3 feet of any lat/long for a start and do your traverse on Topo. It would also give you acerage, but the PI's used on the Deed Plotter would be more acurate. Neat thing about Topofusion, in combo with Faststone software, is you can save it in a Word document as a picture and then describe the enclosure. With Topofusion you can use it with aerials, USGS, and 3-d topos. Great stuff.
2008 F-250 V-10
2007 Lincoln LT
1996 Ford Bronco
Kubota 900 RTV
Shindiawa fan

SwampDonkey

Attached is a spreadsheet with illustrations. I calculated in meters and hectares. You can change the area column to get acres by substituting "10000" (m2) with 43560 ft2 to get acres. A meter is 3.281 feet. You can see my results and compare with the bottom illustration showing the area calculated on a GIS program.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

SwampDonkey

I might as well toss this in here. It was a thinning block, outlined in yellow, that I created a 3D topo map out of. It's actually exaggerated  3-times it's actual relief. You can see a hardwood ridge to the north with a road corridor, it looks sharper in this map than it actually is because of the exaggeration used. You can see contour lines in orange every 20 meters in elevation. This was done using Landsat and creating a TIN file. Then I draped the aerial photo over it. I then compared surface area with map area and the difference was only 0.03 ha on a 45 ha block. I could get a lot more accuracy if I took a GPS point at all slope changes in the perimeter and strip lines. The satellite only took points every 200 meters as I understand it, much courser resolution.

"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

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