THE 2-MINUTE RULE FOR CONTOUR SURVEY

Lastly, the tripod leg must be mounted ready exactly where equally the bubbles are approximately in the middle of their run.An isohyet or isohyetal line (from Ancient Greek ὑετός (huetos) 'rain') can be a line on a map joining details of equal rainfall in a offered period of time. A map with isohyets is referred to as an isohyetal map.– Ph