Difference among ascent, height gain, and height difference

Like change in mood and season, change in altitude that is common in the Himalayas affects all type of activities, including trekking and cooking.  A steep increase in height, for instance, affects speed of trekking. At high altitude, cooking takes longer because of low pressure and temperature. Planning hikes and treks in the Himalayas, therefore, requires clear understanding of gain and loss of height along the routes.

Height gain means the height to be climbed during a trek. The total gain is the sum of all climbs, whereas total height loss is the sum of all descents. Net gain is difference between the total gain and total descents.

Ascent is the total height gain along the hike.

Height difference means difference between the lowest point and the highest point on the trek route. While calculating the difference, height loss (descent) and / or gain (climb) that may occur during the hike are not taken into account.

For example, height of the starting point of trek (A), the lowest point on the route, is 1,000 meters. The highest point of the trek (F) is at an altitude of 2,000 meters.  The trek also ends at F. You climb up 200 meters, go down for 75 meters, again climb up 300 meters, go down for 125 meters, and climb up 700 meters to reach the point F.

Height gain 1 = 200 meters

Descent 1 = 75 meters

Height gain 2 = 300 meters

Descent 2 = 125 meters

Height gain 3 = 700 meters

Total height gain = Height gain 1 + Height gain 2 + Height gain 3

Total height gain = 200 + 300 + 700

Total height gain = 1200 meters

Ascent = Total height gain

Ascent = 1200 meters

Total height loss = Descent 1 + Descent 2

Total height loss = 75 + 125

Total height loss = 200 meters

Net height gain = Total height gainTotal height loss

Net height gain = 1200 – 200

Net height gain = 1000 meters

Height difference = Height of the highest point – Height of the lowest point

Height difference = 2,000 – 1,000

Height difference = 1,000 meters

Net height gain = Height difference

1,000 meters = 1,000 meters

You have thus actually gained 1,000 meters but climbed 1,200 meters that should be taken into account while planning and calculating the time required to complete a hike / trek.  In this example, net height gain and height difference are equal, but it may not be true for all trek routes.

For example, along the above route, if you have to descend 25 meters (G) on the last day to catch the bus to return home, net height gain and height difference will not be equal.

Height gain 1 = 200 meters

Descent 1 = 75 meters

Height gain 2 = 300 meters

Descent 2 = 125 meters

Height gain 3 = 700 meters

Descent 3 = 25 meters

Total height gain = Height gain 1 + Height gain 2 + Height gain 3

Total height gain = 200 + 300 + 700

Total height gain = 1,200 meters

Ascent = Total height gain

Ascent = 1,200 meters

Total height loss = Descent 1 + Descent 2 + Descent 3

Total height loss = 75 + 125 + 25

Total height loss = 225 meters

Net height gain = Total height gain Total height loss

Net height gain = 1200 – 225

Net height gain = 975 meters

Height difference = Height of the highest point – Height of the lowest point

Height difference = 2,000 – 1,000

Height difference = 1,000 meters

Net height gain Height difference

975 meters   ≠ 1,000 meters 