Posted by & filed under Dams, Earth Banks, Surveying, Swales, Terraces.

by Darren Doherty of Permaculture.biz


An example of the results
Click for larger view

I developed a technique in 2007 during a Keyline Design Course at Tuscon, Arizona for making a contour map using cheap available materials. One of our students didn’t have the cash to get a surveyor to do the job on his 40 acres, so I came up with this solution on the whiteboard and have since tested it on the ground quite a few times now.

Using a Bunyip/Water Level, A Frame, Laser Level or Dumpy/Automatic Level mark out a contour line using stakes or pin markers (see below for an alternative to this technique in some circumstances).

Using a Bunyip/Water Level, Laser Level or Dumpy/Automatic Level go down or up the desired elevation (eg. 1 foot or 0.5m) more or less stepping down (or up) each contour interval and then running along until you run out of signal (laser) or come to a boundary or obstruction.

Using a consumable GPS (I have a Garmin Etrex HCx – about $200 worth) record waypoints at each of the stakes. Be sure to wait for the GPS to ’settle down’ reducing its error down to between 1-3m. Hold the GPS out in front of you over the stake and then take the waypoint. You can also take waypoints of important features such as rocky outcrops, dam perimeters/maximum water levels, fences, pipes, buildings, tree drip lines etc remembering to codify/name each point so that the points can be distinguished from you contour points.

You can choose not to use stakes if you like by marking the waypoints directly onto the GPS as you mark each contour point. This reduces the time needed to survey dramatically. If you have livestock then you will most certainly lose many of the stakes anyway as their curiosity gets the better of them!

Using a measuring wheel (or paces if you’re good!) take some ‘ground truthing’ measurements across the site. This will be useful later when you want to rough out the ‘coefficient of error’ from the GPS as there will always be with a consumable model….

Then load the GPS data onto computer. Most GPS units come with a basic mapping program or you can (as I do) use a program like MapInfo, or other GIS or CAD programs. The waypoints will come up marking the pattern of the contours. You can then join the dots and presto you have your contour map.

The image above is an example of the results. For this job I only needed a few contours. The accuracy came in at between 1-3m which over 10 hectares acres is fine in my opinion.

We also now import GPS points directly in Google Earth for immediate viewing. Go to TOOLS then GPS, click off ROUTES & TRACKS leaving ‘WAYPOINTS’ ticked, then click IMPORT. Good idea to make a new folder in Google Earth by selecting ADD then FOLDER. Name the Folder of the Property/Owner name and date etc.. (Or just keep them as whatever Google Earth calls them if you just simply import them.) Click on the new folder so it is active and now go through the GPS points importation procedure as described.

The points will then be shown on your Google Earth map. These points can be exported into programs such as MapInfo Professional by saving these points either individually or as a folder in Google Earth as .kml/.kmz and then using KMLCSV freeware (available at www.kmlcsv.pbworks.com). You then import these points into MapInfo using the Create Points function and then open them in your mapper as a .tab file. Other GIS software provides for a similar process.

8 Responses to “Making Contour Maps on the Cheap”

  1. Stan Depuy

    I’m not having much luck finding out what a Bunyip/water level is.
    I’ve taken a hose filled with water with a foot of see through tubing at each end and viewed the water level to find the same heigth from one spot to another. Is that similar to the bunyip?

    Reply
  2. Robert

    This so-called Bunyip level is simply a clear plastic tubing/hose filled with water. In the Philippines this is a standard tool by carpenters, and is called simply a hose level. I have used it, still use it, in my hydraulic ram pump projects (site surveys and installations). But here, we use an entirely clear/transparent hose– so that bubbles along any section can be seen and removed. If only the two foot-long ends are transparent, bubbles that form in the non-transparent sections can’t be seen and this could result to inaccurate readings. Hose levels are low-tech but simple, very portable and effective. I call them GPH (Global Positioning Hose).

    Reply
  3. Bill

    If you have the laser or optical level, you can place a lattice of points over your area. A regular square grid is easiest, and you can use a tape down one of the lines to keep people in position. Pacing is sufficient, and with a positional error of about 1 to 3 m, it is at last as good as a hand-held GPS, if not better.

    If you want to look at the errors, change the vertical values at a point, and re-compute the volume, looking at the differences. A change in horizontal location will cause smaller errors than changes in a vertical value, if the surface is not very steep.

    If you can get enough hose, you can do the leveling with the water level (bunyip level, hose level, water level, or hypsometer), but an optical level and staff/rod or laser level and staff/rod can be a lot quicker and easier, especially if the ground is reasonably level.

    The advantage of a regular square grid is that the computations are much easier. You can do it easily in Excel, or on paper, but if your points are irregular, you introduce a lot of computational overhead, with the chance of significant gross errors.

    If you are looking at a low-tech solution, keep it simple all the way. Don’t complicate things unnecessarily, and just because there are a few high-tech pieces of gear in the overall system doesn’t mean that the errors are any less. They just hide differently. Computing volumes has a fairly high error potential, simply because you can’t measure every point, so you are looking to get the result to within 1-2 truckloads of dirt, 10-20 m^3 or yd^3.

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  4. Darren J Doherty

    G’day, not a bad way for a smaller area Bill, though this method involves more than one person and would take a lot more time.

    A colleague of mine earlier in the year did a 200ha 2m survey of a farm in Mexico in 2.5 days…got back to the car loaded up the points onto his laptop and then hooked onto the internet via his 3G stick and posted the points to me….the results can be found here (http://picasaweb.google.com/lh/photo/gg_32Jr5ITq2owOSVqIg9w?feat=directlink)….

    I should add that the most important thing to survey when intending to do cut & fill earthworks is to survey not using the grid method but along ‘tops and toes’.

    Grid surveying using the method Bill has described is something I did back when I started the Permaculture journey and our 1st job financed a dumpy level. My partner at the time, Michael Heenan (also my brother in law) and I surveyed a clients undulating property and had a lot of fun doing it but boy it was a pain….important thing was that we missed so much of the actual topography as a result of taking ‘shots’ on the grid and not on the landscape tops and toes.

    Our intention is to use this method to give us a better than government map topo map (often 10-50m contours!) using relatively cheap and available equipment. We can then get a better idea of the patterns of the landscape and design a plan accordingly.

    At the end of the day however the old adage of ‘the map is not the territory’ comes in and we still use a design as a guide which then informs us as to a set out which is based on the land on which we stand and measure accordingly.

    Best thing to do is to know all of the basics, which includes the method Bill described, as machines do fail and we have to fall back on other techniques occasionally.

    All the best,

    Darren

    Reply
  5. Darsa Bhikkhu

    Thanks for that info. Another way, for larger propreties, as the contours are 20m apart:

    Get the property on Google Maps (“classic” map view)

    Check “Terrain”

    Zoom to the 1000ft/200m view – this is the closest you can go and get contours

    Print it out

    Swap to satelite view and don’t move the map or change the zoom

    Print it out

    Mark on the printed satelite view the corners or boundary of the property

    overlay the map view onto the satelite view and mark the corners or boundary onto the map view

    scan the map view with marks

    in a graphics program (or with a photocopier, scissors, glue and white out pen): enlarge the scan and move the 1000ft/200m ratio indicator closer to the property; change to greyscale (B&W) and whiteout other shading around contour lines and corners/boundary

    You might want to do similar with the satelite view if you want to overlay them.

    there you have it

    Reply
  6. Blake H

    Im currently using this method for a job, and so far so good! Im using a Bosch tripod site level, garmin gps, google sketchup with KML importer plugin: http://sketchucation.com/forums/viewtopic.php?t=38009
    The problem I have is the excising vegetation is getting in the way to continue plotting waypoints on some contour’s. There are still a few tricks to be learnt and will know them all shortly. Im creating a 2m contour map over 14 acres.

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