Creating contour maps of a large property

Discussion in 'Designing, building, making and powering your life' started by DJ-Studd, Sep 28, 2010.

  1. DJ-Studd

    DJ-Studd Junior Member

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    Hi Guys,
    what would be the most economical way to create a detailed contour map of a property between 100 and 200 acres in size?

    Are there GPS units that you could mount to the back of a vehicle and drive the property, taking waypoints?
    Is aerial surveying cost effective?

    There are no government maps as far as I am aware.

    Cheers.
     
  2. sun burn

    sun burn Junior Member

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    what about google maps?

    Are you sure there are topographical maps of your area? Have you been to the lands department?
     
  3. DJ-Studd

    DJ-Studd Junior Member

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    Unfortunately the property falls outside of the metropolitan surveying and the countour lines available are at 100 metre intervals... not much use really!
     
  4. adrians

    adrians Junior Member

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    100m contours? are you sure? that would be for the 1:250 000 maps, what about 1:25 000 or 1:50 000?

    there are 1:25000 topographic maps for large areas of australia, usually with contours at around 10m.. is that enough? probably not I guess, but it woudl be a start, these maps are usually about $8.00..
    Do you know the name of the map covering your area (look here https://www.land.vic.gov.au/Land/lc...56D660019A51416D5A1DCB4D6FC324A256A5D0025B15A)

    You're right though, the more accurate maps such as orthophoto maps aren't available in alot of areas..
    other options:
    - you could look into hiring a "differential GPS" this is the type you would need to create a contour plan.. not sure of the costs, you would need to know your way around a contouring package such as surfer to creat the contour plan though :-(
    - hmm, not cheap either.. eg https://www.keyline.com.au/key1maps.htm
     
  5. DJ-Studd

    DJ-Studd Junior Member

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    Thanks Adrian. Land Vic have 10 metre with the correct map layer enabled. It's a start, but realistically I need much more detailed. Keyline are in QLD so I'm not sure how much use they will be in Victoria. Perhaps I need to find someone in Vic that can do Aerial mapping. I have emailed Darren Doherty and will see what he suggests.

    Cheers
     
  6. permup

    permup Junior Member

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    Hi

    I have a client who has taken thousands of GPS coordinates of his property and is now grappling with turning them into a contour map. My next step was to ask Darren too, so looking forward to what he tells you DJ. The contour maps provided free of charge are just not good enough to plan keyline from.

    Paula.
     
  7. DJ-Studd

    DJ-Studd Junior Member

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    Hi Paula,
    that was going to be one of my options, but as with you the question is what do you do with all of the GPS waypoints?

    Cheers
     
  8. permup

    permup Junior Member

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    I thought it would be as easy as importing all of the latitude and longitude points, with the elevation, into a software tool, and out spits a wonderful contour map. I found a couple of online tools purporting to do just that, but they didn't work for me. I've contacted a surveyor who reckons you have to do it manually, but THAT'S not going to happen!
     
  9. adrians

    adrians Junior Member

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    you should be able to use a program like surfer, it is a contouring program.. unfortunately not sure what free ones there might be out there.
    permup.. if you send me the data file I'll have a go at contouring it for them, I don't have the software surveyors use though.
     
  10. PeterFD

    PeterFD Junior Member

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    Hi Dj-Studd

    I have about 100 acres on the side of a mountain in the French Alpes and have tried to work with contour maps to locate positions for swales, dams etc.

    A couple of years ago I bought an electronic device that gave an indication of altitude using changes in air pressure (a bit like the systems originally used in aircraft). Unfortunately it was necessary to take several readings over several days to get some idea of actual altitude.

    This year I started to install my first swale and soon realised that contour maps have no respect for forests, trees, boulders and rocky outcrops that are all to frequent in my location.

    Contour maps, even basic ones, are fine as starting points, however there is no escaping the actual physical work of plotting a contour. So, I built my first “A-frame”, attached a spirit level to the cross-bar and set to work.

    The first thing I discovered is that although under my left foot I may have a nice sandy loam, possibly a meter in depth, under my right foot I may have the start of a 60 foot boulder/rock formation which is impossible to cut through.

    My only conclusion was that to gain a realistic overview of useful contours on my property I would have to do the job myself no matter how time consuming or tedious.

    However, recently I discovered, via www.ebay.fr “Globalstat DG-100 USB GPS Tracker Logger” available from DigigoMart. This device allows up to 60,000 GPS latitude/longitude/altitude readings for 45 pounds UK including postage world-wide ( about 72$ or 74 Au $) including USB cable to upload data to computer and software.

    There is some sort of export/interface to Google Maps/Google Earth (KML?) but you will need to buy the software or locate open-source.

    When my piggybank gets a bit fatter in the next month or so I’m going to look into this approach.

    You can google on the name of the device, however, if you need the ebay France reference I can provide further information.

    I would certainly be interested in Darren Doherty’s response so hope you can post!

    If I have understood the specifications correctly, once I have marked-out the respective contours, I can use the data logger to record the exact locations (possibly metre by metre) via GPS and upload this information onto my computer. The opportunity then presents itself to plot this data on a Google map.

    Hope this all make some degree of sense,

    Peterfd
     
  11. adrians

    adrians Junior Member

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    Peter, at that price, the GPS is a standard GPS, not a differential one, the accuracy of elevations measurements for a standard GPS are usually not accurate enough (a few metres rather than a few mm or cm).
     
  12. DJ-Studd

    DJ-Studd Junior Member

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  13. PeterFD

    PeterFD Junior Member

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    Hi Adrians

    You’re right, its just standard GPS, nothing fancy for the price. What attracted me to this Globalsat device is that it allows 60,000 recordings, has a USB connection to a computer and some software thrown in. Not bad for the price. Most others I came across for the same money allowed 16 recordings and no USB.

    I checked on DJ-Studd’s link provided by Darren, seems similar to the type of approach I was evolving towards with an “A-Frame”. However, his idea of plotting the actual swale/dam etc., with a GPS data logger, such as the Global sat, onto a map would hopefully give an excellent presentation and be worth the small investment.

    If you get a moment, could you give some idea of how the Differential unit works-out the altitude to such a high degree of accuracy?

    Thanks,

    Peterfd
     
  14. adrians

    adrians Junior Member

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    a differential gps, is a big unit used by surveyors etc, it works based on error correct based on broadcast signal (which you have to "hire") I don't know any more than that, sorry.

    Yes, the idea of GPS for E, N and level for RL sounds very suitable.
     
  15. LittleFish

    LittleFish Junior Member

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    Hi there
    If I was you I would talk first of all to your local CMA. Over here at the Wimmera we have the entire region aerial laser mapped down to a 1 metre level. Not sure what its like over that side of the state but us GIS people in the CMAs are usually a good resource for any land mapping issues.

    Be aware that your hand held non-differential GPS has a horizontal accuracy of about +-5 metres and vertical accuracy can be worse than that.

    For a super cheap but time intensive method of contour mapping your best bet would be to use a water level - anchor one end to a "reference point" and then measure the rise or fall relative to that point. Start with maybe 5 or 10 metre radius sample lines depending on the size of the block to be surveyed.
    Hope that helps
    cheers
    Steve
     
  16. Terra

    Terra Moderator

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    Just buy a "Dumpy" level and tripod and staff about $400 starting point or spend as much as you want , lazer gear is fine and yes you can do it unassisted but you just end up walking miles for nothing do it with a friend in your own time , easy , my wife and i have done contours in all the paddocks on our 1100 acre farm . Its not super high tech fiddle with GPS computer program work just getting out there and walking your land , its really interesting trying to guess where to go with the staff after awhile you get pretty good and the level operator just has to fine tune your position . They are a fantastic tool to have mine is damaged at the moment (lent it to others and the focus gear is stripped ) i really miss it ,costs more to repair than replace (typical) . On 200 acres we could mark 10 metre contours in a couple of days easy , if all you want is levels we would mark at 15 metre spaces with a piece of paper with a rock on it and then shallow rip the line so you can see it easy , do maybe three across your land and then have a good look at whats happening if you want to retain the mark deep rip it , lasts for ages cetainly long enough to do your planning or drive pegs in . If your looking to move water around , research how much fall your soil can cope with the original ones that Primary industries did for me were too flat and water seeped straight through they silted up on corners ran over erosion big mess ect ,so we do them a bit steeper now and put more fall on the tight corners (water slows here and will drop silt with disasterous effect) . So as is often the case if you want something done properly do it yourself , we filled them in and started again . Also research local regulations on moveing water around more rules every year of course with $$$ FEEs attached . In our case interceptor contours (drains cut into the soil anda bank on the down slope edge ) were the best option to control wet areas so you could get machines over the paddocks . Same principles apply on small scales handy tool for backyards as well eg building neat square chook pens making swales .
    Terra
     

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