Land Surveying Basics: An Easy, Cheap Land Surveying Process Explained
Tackle land surveying basics early in the farm development process with this cheap land surveying process explained here for setting out farm buildings,
earthworks and dams.
Land surveying begins with constructing yourself an accurate but cheap land surveying instrument. Such an instrument is the Hose Level, which you can easily make for the princely sum of about $60.
MAKING A HOSE LEVEL
You will need:
• 2 x 2.2 meter long sturdy hardwood stakes
• 2 x 2 meter measuring tapes (we paired up 4 cheap 1m dressmaker’s tapes)
• 4 meters of clear plastic tubing with a ½ inch (13 mm) inside diameter
• 30 meter non-kinking garden hose (the higher the quality the better): This is the single biggest expense - ours cost $35.
• 2 joiners to join the hose ends to the plastic tubing
• 2 in-line taps to suit the plastic tubing
• Nails or glue to secure the tape to the stakes
• Wire or zip-ties to secure the tubing to the stakes
• Water colored with food dye
To make your cheap land surveying instrument, simply:
• Glue, nail or staple the measuring tape securely onto the stakes, taking care that each is in exactly the same position on each stake. Use the flat end (i.e. not the pointed end) of the stake as the bottom for sitting on the ground when you start to use your finished Hose Level.
• Divide the clear tubing to produce two pieces of equal length (about 2 meters each).
• Cut each length of tubing again to produce one of 1.3 meters long and one of 0.7 meters long, then rejoin them using the inline taps.
• Secure each length onto its stake using wire, tape or zip-ties so that the top end of the tubing is a few cm (an inch) higher than its respective stake. Insert your joiners into the other (lower) end of the tubing.
• Fill the garden hose with water.
• Use the joiners to join the ends of the tubing to the garden hose to complete your Hose Level.
• Open both taps and top it up with a jug of water to which food dye has been added.
• Close the taps and store upright when not in use.
LAND SURVEYING BASICS: USING A HOSE LEVEL
For a cheap land surveying tool, the properly constructed Hose Level is very accurate. It utilizes the principle of physics that water in an open container (such as a hose) will always settle at the same level. Its only disadvantage over more sophisticated tools such as laser leveling devices is that 2 people are needed to use it.
Before you begin use a level surface to check that both ends of the Hose Level are registering the same level.
To do this, and whenever taking readings, move your ends to the desired location with the taps closed, then open them to allow the water to find its level and give you the reading. Air bubbles in the line distort the accuracy of the Hose Level and can result in a false reading.
If you find the Hose Level is not reading correctly, you’ll need to get the air bubbles out.
The best way to achieve this is to fill the level with water, close the taps, and place one stake in a slightly more elevated position than the other. Open both the taps, and thump the bottom of the lower stake onto the ground to encourage any air bubbles to rise up and escape from the higher stake.
You may have to repeat the process a few times. Avoid air bubbles forming by closing both taps whenever moving the Hose Level around.
Once your Hose Level is operating properly, measuring the difference in elevation between two points is readily accomplished. Since the water in the hose level will always return to level when the taps are opened, the difference in the water level tape reading on your calibrated stakes will give you the true difference in elevation between the two points on the land.
In the photo opposite, the reading for the stake placed on the bucket was 1.48 meters, and for that more lowly placed on the ground was 1.72 meters. So the height difference between them was 1.72 – 1.48 = 0.24 meters.
SURVEYING A SITE: THE LAND SURVEYING PROCESS EXPLAINED:
The topography or shape of the land needs to be known beforehand for a range of site works: for siting a building, planning excavations, or staking out earthworks, banks and dams. So here we describe land surveying basics that can be used to plan any works on your property.
You can develop a map of the undulations of building site, for example, by using your Hose Level to measure elevation at several points across the site.
The Grid method of surveying a site:
Use stakes to mark out a regular grid pattern on the site. The amount of detail required determines the size of the grid. For preliminary work a grid of 2m x 2m cells would suffice.
Use the Hose Level to determine the difference in height between each point on the grid and record these readings onto a drawing of your grid. So you don’t confuse your results, link each pair of readings by circling them and linking them with a line.
Select one point on the grid to be your “zero” (the lowest point is most convenient) and then mark each difference in height relative to that onto graph paper. This will result in a statistical representation of the topographic variations in elevation over your site. Connecting points of equivalent elevation will produce a contour map of the site.
The Degree method of surveying a site:
This method for land surveying basics is useful for when you reach the stage of more detailed site works. In this example we describe the procedure for marking out a site for a solar passive home.
• First determine the direction of ‘true North’ (read this as ‘true South’ if you are in the northern hemisphere). You can use a compass for this. Another method is to consult a newspaper for the times of sunrise and sunset. Midway between these times the sun will be at ‘true North’, and the shadow cast by a stick driven into the ground can be marked out to produce an accurate North-South transit line.
• Mark out the North-South transit line with stakes
• At one end the N-S transit line select a convenient “zero” point on your site. Mark this securely with a solid stake. This point becomes the centre point of a semi-circle.
• Divide the semi-circle into 12 equal sectors (each of 15 degrees) and mark the ends of these “sector lines” or rays of the circle on the outside of the circle with stakes.
• Start surveying the site: One person stands an end of the hose level at the “zero point”, while their partner moves away along a “sector line” ray until there is a difference in elevation of 3 cm (or 1 inch). A measuring tape is used to find the distance from the “zero point” of this 3cm change in elevation, and this is recorded onto a sector drawing of the site. The partner then carries on along the same “sector line” until a point with an elevation of 10 cm (or 6 inches) difference from the “zero point” is reached and the distance to the “zero point” is again recorded. And so they continue on the “sector line” measuring the distance to each 15 cm change in elevation until they are outside of the vicinity of the house site.
• Repeat the process for the N-S transit line as well as each “sector line” rays of the semi-circle.
You could record your results on a Table like this:
How to transcribe your readings to produce a contour map of your site:
• Start with a large sheet of graph paper having a convenient grid of 5 squares to the cm (or to the inch for imperial people). Select a suitable scale – say 5 squares to equal a meter (or 1 square to equal a foot).
• Use a pencil and ruler to lightly but accurately sketch in your site semi-circle with its “zero point”, N-S line, and 15 degree rays of the “sector lines.”
• Abiding by your scale, along each “sector line” mark in the points where the elevation varied from the “zero point” and the appropriate distance from the “zero point”. Lightly label each dot with the associated change in elevation (e.g. – 15 cm, + 3 cm, etc).
• For the purposes of building the area that differs in elevation from the “zero point” by 3 cm or less is considered as level with it.
• Once you have transcribed all your readings onto the graph paper, connect dots of like elevation with gently curving lines to produce an accurate contour map of your site.
All the work involved is worth it for the headaches it will save you in the long run. Use your contour map to find the best location for your building by drawing its foundation footprint to the same scale on a piece of clear plastic and sliding it around on your contour map until the ideal location is determined.
That’s cheap land surveying...
Hope you have enjoyed these land surveying basics and feel confident to DIY!
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