Levels, Surveying and Booking Sheets

Why do we take levels?

It is not common to have a perfectly flat site and if we do then we would have water pooling across it. So, when we take a site analysis, we need to survey the levels, employ someone else to, or acquire existing site levels from previous works on the site. This allows us to design taking into consideration changes in height to allow for retaining, stairs, ramps, and drainage.

How do we describe levels?

In garden design in Australia, we use millimetres for a lot of our documentation. Generally, though we use metres for boundaries and levels. When noting levels, we are trying to describe the height of on point or plane in comparison to another. We can do this relative to the height of sea level or for small jobs we can use something like the internal floor of a house as the reference point.

How to record levels

These days the most common way is to use a laser level. The base device rotates a prism bouncing a laser beam out on the horizontal plane. The lasers now commonly level themselves if they are within approximately 5 degrees of horizontal when you turn them on.

A receiver is then used to work out where that same horizontal plane is at any position on the site. The receiver is moved up and down as it become close to height of the horizontal plane it starts to beep. When low they commonly beep fast, and when high they commonly beep slowly. Once the receiver is at the same height as the laser in the horizontal plane it turns to a continuous sound. You now know that you are at the same height as the laser. Now we can compare how high or low different points are within the site in comparison to this horizontal plane.

Estimating Levels

There are different methods that can be employed rather than using a laser level or dumpy level.

String Line Bubble

In this method you pull a piece of string taught over a garden space and tie it on to two points. You place a string line bubble at the midpoint of the string. A string line bubble is a tiny spirit level that hangs off the string. You move one of the ends of the line up and down until the bubble is in the centre of the marks telling us it is level. Once level you can measure down from the string to the ground along the line and record the difference in height.

Water Level

This is a technique still used in parts of the world. You fill a length of transparent plastic tube with water. When you leave them still the water will equalise to be at the same height at each end. You can keep one end stationary and get the water to level with a marked point. You can then measure down to the ground at the end moving around the garden.

Visual Ques

If you are waiting to receive height data, you can use some visual ques on the site to help you estimate heights. You can count bricks, block and weather boards and note how many are exposed across a contour.

Contours

Spot Levels

Spot levels note the height of a single point.

FFL - Finish Floor Level

TOW - Top of Wall

BOW - Bottom of Wall

Booking Sheets

Lesson Outline

• Why do we take levels?

• How to record levels

• Booking sheets

Presentations

Activities

Grading and Contours Exercise