Congratulations, you have purchased a block of land and now you want to start construction.
However in order to get the plans are drawn you are going to need to get an idea of the slope or fall of your land. This will allow you and your trades, especially the excavation trades, to work out how much material they will have to move in order to get to the levels or depths required.
The grid survey is achieved by taking levels in a grid pattern across the site, recording the levels and booking the Reduced level of each point.
- Mark out the grid pattern on the site.
- a grid pattern of 5m x 5m is generally accurate enough for a residential site
- when marking point on the ground you can use surveyors paint, a brick, chalk or lime, it doesn't really matter as long as you can find the mark again later so you can take the reading.
- This can be done with a combination of measurement and visual alignment.
- the setout should be conducted as accurately as possible however these point can be off by 150mm to 200mm without affecting the accuracy of the survey.
- Make sure that you identify each intersection so you can reference it later. This can be achieved by assigning a letter to grid lines in one direction (say East -West) and a number to the grid line running at 90 degrees (North- South) see below.
- Using the instrument of your choice take readings at each point and record them on to a booking sheet. See my video ‘Taking Levels’ for more information on how to do this.
- Make sure that you record where the reading was taken in the remarks column.
The grid survey is now complete but how do we put it to use? See Contours and Contouring from Grid Surveys.
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