Topographical lines
Called both Elevation Lines or Contour Lines
I think it's an index contour, but I'm not sure.
A contour line on a topographic map is typically labeled with the elevation in round units. This helps to indicate the elevation of the land and the change in elevation across the map.
Contour lines are typically labeled with their elevation, indicating the vertical distance above a reference point, such as sea level. This allows users to easily determine the elevation profile of the land or terrain represented on a map.
"contour lines"
Elevation contour lines.
To determine elevation on a topographic map, look for contour lines that connect points of equal elevation. The elevation can be found by reading the numbers on these lines. The closer the lines are together, the steeper the terrain.
Contour lines show elevation on a topographical map. These lines connect points of equal elevation above sea level, with lines close together representing steep terrain and lines further apart indicating gentler slopes.
Mountains on a map are usually depicted with contour lines or shaded relief to show their elevation and topography. The lines are drawn closer together to represent steep slopes and farther apart for gentler terrain. Peaks are indicated by closed contour lines with the elevation labeled.
Contour lines or also known as isohypses, connect points of equal elevation on a map. Contour lines can be curved, straight or a mixture of both. The lines on a map describe the intersection of a real or hypothetical surface with one or more horizontal planes.
A topographic map shows the elevation of the Earth's surface using contour lines to represent changes in elevation. The closer together the contour lines, the steeper the terrain; the farther apart, the gentler.
Brown lines