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digga
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Joined: Feb 05, 2005
Posts: 7
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 Posted: Sat Feb 05, 2005 4:31 pm Post subject: working out the area size of a piece of land with gps? |
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 hi i am a total newbie to gps but i have a question i was wondering if anyone could help me with or offer me some advice on
the question is i do a lot of woodcutting in my job and get payed by the acre what im wondering is there a gps type system that i could walk around the perimeter of the block of wood i have just cut to work out the
Acreage that i am owed for and if so what would be the best system and way to go about it and a rough idea on prices ? like i said im a newbie to gps so any help would be very greatfull many thanks |
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MarkHewitt
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Joined: Nov 16, 2004
Posts: 1077
Location: Chester-le-Street & York
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| Posted: Sat Feb 05, 2005 6:02 pm Post subject: |
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| If you have a system such as memory map you can use GPS to plot locations or a track and then work out the distance between the points and hence the area. |
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digga
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Joined: Feb 05, 2005
Posts: 7
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| Posted: Sat Feb 05, 2005 10:08 pm Post subject: hi thanks for the reply |
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hi mark thanks for your reply like i said im a total newbie to gps so was wondering how the set up you was saying about sometimes the block i need to measure can be as small as half an acre or upto 10 acres in one block ? i wouldnt be sure how to get the points and how many i would need for memory map to work out the area its not to hard to work out on pen and paper on evenly shaped blocks  but odd shape ones are hard to do so thats why i was looking at gps to see if it is an easy solution to working it out ? any help is greatfull |
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MarkHewitt
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Joined: Nov 16, 2004
Posts: 1077
Location: Chester-le-Street & York
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| Posted: Sun Feb 06, 2005 10:33 am Post subject: |
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I guess like any area you need to plot the points at each of the corners, once you've done that you can work ou the area with some graph paper and a calculator  No doubt there are packages to do that for you but this seems the cheapest way. Note however it doesn't take into account gradient, if that is important to you? |
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LeighB
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Joined: Jan 23, 2005
Posts: 156
Location: Ipswich Suffolk UK
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| Posted: Sun Feb 06, 2005 12:16 pm Post subject: |
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Hi,
I am not v experienced with Memory map, but I believe that if you plot Marks at all the angles of the area you are interested in, then create a Route using all these Marks and finish where you started, the Route Properties will show the area enclosed by the Route.
This is certainly the case if you create a Route to send off for the 1:25000 Selectons, you need to check the area in Properties to make sure you have not exceeded, but are close to the 2,500 sq km. If you use Imperial Units I suppose the area would be expressed in acres or sq miles?
Hope this helps
Leigh |
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MarkHewitt
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Joined: Nov 16, 2004
Posts: 1077
Location: Chester-le-Street & York
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| Posted: Sun Feb 06, 2005 1:04 pm Post subject: |
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| One thing, I believe you can get the memory map software for free, and it's just the maps you pay for? In this case then 'digga' would only have to download this software, as having a map (although useful) would not be essential for his requirements. |
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digga
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Joined: Feb 05, 2005
Posts: 7
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| Posted: Sun Feb 06, 2005 11:08 pm Post subject: hi thanks for the help |
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| hi thanks for the advice like i said some blocks i have to measure are some very funny shapes so im guessing i would have to take a reading at every angle change and corner and would i be right in thinking the more points i put in the more acurate the measuring of the block will be ? was wondering what kind of system farmers use on there machinery to work out field sizes and stuff ? allso could anyone recomend a good hand held gps for ploting the points with ? guess im going to have to look into this a bit more yet many thanks |
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MarkHewitt
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Joined: Nov 16, 2004
Posts: 1077
Location: Chester-le-Street & York
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| Posted: Mon Feb 07, 2005 12:16 pm Post subject: Re: hi thanks for the help |
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| digga wrote: | | hi thanks for the advice like i said some blocks i have to measure are some very funny shapes so im guessing i would have to take a reading at every angle change and corner and would i be right in thinking the more points i put in the more acurate the measuring of the block will be ? was wondering what kind of system farmers use on there machinery to work out field sizes and stuff ? allso could anyone recomend a good hand held gps for ploting the points with ? guess im going to have to look into this a bit more yet many thanks |
Yes, the more points you can take the more accurate your result will be. Ideally if you can ensure accurate GPS reception for your entire area you should load up memory map, get a GPS lock and walk the entire perimiter of the area, then get it to save the track. When you get home you can upload this to your PC.
I've just tried that now manually drawing a track by hand, and I selected "Track is a closed loop" and it told me the total area in acres, which I think is just what you are looking for.
From what I know farmers usually don't go to all that trouble, they usually get a detailed map of the premises and work it all out on paper, of course you could do the same.
Be aware of the limitations of GPS however, I believe the accuracy is something like 10 metres these days, so don't expect to be able to use GPS to be able to map out areas of only a few metres square, cos it won't work. . As for what you will require, I believe you already have a PDA? Well you can get either a bluetooth GPS or a CF GPS (if your PDA has a CF port, and run the whole thing on your PDA |
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barryd
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Joined: Mar 27, 2004
Posts: 285
Location: Cheshire, England
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| Posted: Mon Feb 07, 2005 2:10 pm Post subject: |
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Just a note that OziExplorer can also do this area calculation for you from a GPS track, much as has been described above for Memory Map.
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Barry Davies
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Skippy
Pocket GPS Verifier
Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
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| Posted: Mon Feb 07, 2005 8:32 pm Post subject: Re: hi thanks for the help |
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| digga wrote: | | allso could anyone recomend a good hand held gps for ploting the points with ? |
If you just want a hand held GPS to measure the area and you are willing to walk around the border then you can get a cheap Garmin GPS for <100 pounds which will record a track log and tell you the area.
The basic models don't display maps but they will record a track and tell you what the area inside the track is. More advanced models will display maps that you can upload.
A street routing GPS like the Garmin Quest can be had for £350 and will do turn by turn routing with voice prompts and maps of all of Western Europe.
Note that you can only load Garmin maps on Garmin GPS units, (you can't load an Ordinance Survey map into the GPS)
If you want the full monty, then get a PDA and a Bluetooth GPS receiver and Memory Map or Fugawi software. You can then display Ordinance Survey maps on your PDA screen (download the OS map you want from somewhere like www.multimap.co.uk or buy them with Memorymap). All up this would be 400 pounds or more.
Good luck making a decision and tell the supplier what you want it for to make sure the specific unit you are buying suits your needs.
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Skippy
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Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
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| Posted: Mon Feb 07, 2005 8:49 pm Post subject: Re: hi thanks for the help |
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| digga wrote: | | some blocks i have to measure are some very funny shapes so im guessing i would have to take a reading at every angle change and corner and would i be right in thinking the more points i put in the more acurate the measuring of the block will be ? |
Most GPS units can record a "Track Log" which means it will record your position periodically. If you are moving in a straight line at a constant speed then it may record a position every 10 seconds but if you go around a corner then it will increase the resolution to one sample per second.
So you don't have to manually add the points, just switch your GPS on, make sure it has a good view of the sky and off you go.
Note that GPS doesn't work well under heavy foliage or if you are in a steep canyon or surrounded by tall buildings. Even in difficult conditions it should give you a reasonable approximation of the area though.
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digga
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Joined: Feb 05, 2005
Posts: 7
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| Posted: Wed Feb 09, 2005 10:28 pm Post subject: thanks |
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| hi thank you all for the help and advice you have given me guess im going to go shoping for a handheld gps hope i can find one that i can plug into my home pc when i get back home so i dont need to buy a pda as well ? think i will try go for a model that offers mappingFacility as i will need to be able to have some form of a printout to show to my clients so they can check the measurements for them selfs can see gps is going to be a learning curve but a fun one to :D |
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Skippy
Pocket GPS Verifier
Joined: 24/06/2003 00:22:12
Posts: 2946
Location: Escaped to the Antipodies! 36.83°S 174.75°E
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| Posted: Thu Feb 10, 2005 1:00 am Post subject: Re: thanks |
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| digga wrote: | | hope i can find one that i can plug into my home pc when i get back home so i dont need to buy a pda as well ? |
All but the most basic hand held GPS units can connect to your PC to upload the "Track Log" and any waypoints you have recorded.
| digga wrote: | | I think i will try go for a model that offers mappingFacility as i will need to be able to have some form of a printout to show to my clients so they can check the measurements for them selfs can see gps is going to be a learning curve but a fun one to :D |
Bear in mind that the Garmin mapping GPS units will only take the Garmin maps and these only show roads - they are no where near as detailed as the OS maps.
The good news is that you can upload the track log or waypoints from the GPS onto your PC and use a topographical mapping program for your PC to overlay the track log onto the Ordinance Survey map.
You can then print off the map with the overlaid track log and waypoints for a very professional looking result. 8)
Have fun!
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oddsock
Pocket GPS Verifier
Joined: May 01, 2004
Posts: 706
Location: Monmouthshire
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| Posted: Thu Feb 10, 2005 4:08 pm Post subject: |
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| MarkHewitt wrote: | | If you have a system such as memory map you can use GPS to plot locations or a track and then work out the distance between the points and hence the area. |
Would this be accurate if the land was on a slope?? I ask this because during the 1960's I worked in forestry clearing ground for re-planting (by hand with axe and crosscut saw ), we were paid by the acre (£40) and worked out the area in chain widths (22yds) this was a more accurate way of doing it as the map area of a given wood was far less an area than that we had measured by our method (but only if the land was on a slope)
Dave |
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digga
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Joined: Feb 05, 2005
Posts: 7
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| Posted: Thu Feb 10, 2005 7:56 pm Post subject: on a slope ? |
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hey I had never even thought as to if i would be as accurate on a slope as on the level ? but it is a very good point as oddsock pointed out there are 22 yards in a chain and 10 chain to the acre that’s how I normally work it out when i measure it with a wheel and work it out on paper its not hard to do on fairly regular shape blocks of wood but can be a headache on some blocks
it got me starting to think if there was an easier way of working it out and gps came to mind and from what i have learned from this forum and the good advice ive been given (many thanks to everyone again)
it looks like it is very possible to walk around the boundary of a block with a gps and work out how many acres are in it and if you can look more professional in front of a client its always a good thing  like i have said before i am a total newbie to gps but think even i can work it out with the advice ive been given :D so just now need to decide on what hand held gps to get and i also like the idea of what Skippy said about the track log or waypoints from the GPS onto myPC and use a topographical mapping program for your PC? to overlay the track log onto the Ordinance Survey map.
You can then print off the map with the overlaid track log and waypoints for a very professional looking result as i will need a print out of the measurements to show the client any suggestions on software to do this: D |
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