# Ancient Egyptian Surveying

### From DT Online

Egypt is regarded as the home of the first known Surveyors. Surveying was necessary in Ancient Egypt because the annual floods buried or destroyed boundary markers, which then had to be re-established for ownership of the fields.

The Egyptians developed a system of measurements based on the human arm:

• Cubit = the length from the bent elbow to the tips of the fingers;
• Palm = the width of the palm of the hand;
• Digit = width of the human fingers.
• Rod or Cord = 100 Cubits

So four Digits equal one Palm and seven Palms equal one Cubit - the wooden Cubit Rod, one Cubit long, was marked in Palm and Digit divisions and used by Architects and Surveyors as we now use our modern Rules.

The Egyptian phrase for a surveyor was a Rope Stretcher and surveying was known as ‘stretching a rope’ - a rope or cord calibrated with knots placed at regular intervals, was one of the tools used in surveying larger distances (measuring cords may have been 100 Cubits long since since the number 100 is represented by a picture of a rope in Hieroglyphs - any longer and the cord might have been too difficult to stretch tight).

It is thought that the Ancient Egyptians were not familiar with what we now know as the Pythagoras' Theorem but it seems their knotted cord or rope enabled them to set out right angles using the special case of a 3-4-5 Triangle and testing for Square by checking the Diagonals.

The main unit of area was the Setat. This was equal to one square Khet (aka Rod or Cord) of 100 cubits. The Setat could be divided into strips one Khet long and ten Cubit wide.

In addition to Cubit Rods and knotted Cords, the Ancient Egyptian surveyors used Builders' Squares, Plum Bobs, Gromas and Square Levels to check for Squareness and testing for vertical or level. Checking that long distances were level may have been achieved by filling trenches with water and alignments with stars established using a device known as a Merkhet.

Using such basic equipment the Pyramids were built and aligned with astonishing accuracy. The Great Pyramid at Giza (Khufu) has been measured at 231 meters square and the largest discrepancy is 30cm between the north and west sides - but the difference between the north and east sides is only 6cm!

Each of the pyramids at Giza have the same slope angles. They are aligned very accurately to the north-south axis and in relation to each other except that the smaller Pyramid of Menkaure is offset. This gave rise to a theory that the group of pyramids is designed to reflect the star constellation of Orion and that the internal passages of Khufu point to certain stars - but this theory is not generally accepted.

Activity: Make some model Ancient Egyptiian survey tools and survey your own room - or house. What are the dimensions in Cubits? Is everything vertical or horizontal? What is the area of your garden in Setats?