The survey was a collaborative effort between the NLSI, the Icelandic Coast Guard and the Institute of Earth Sciences. Because Hvannadalshnúkur is a glacier the NLSI plans to measure the height of Hvannadalshnúkur every 10 years.

Surveys on glaciers
Because Hvannadalshnúkur is a glacier its height varies within the year. The height is therefore more after a heavy winter than in the fall when the temperatures have been higher during the summer and melted the snow.

History of the surveying of Hvannadalshnúkur
Source: Þar sem landið rís hæst by Snævarr Guðmundsson

The height of Öræfajökull was a fascinating secret for centuries and for a time Öræfajökull was considered to be among the highest mountains in Europe. This point of view was documented in a report from 1776 by Sæmundur Magnússon Hólm, one of the biggest Icelandic mapmakers in the second half of the eighteenth century.

1794
Sveinn Pálsson was the first man to make an attempt to walk on Öræfajökull. He walked up to a peak that is now called Sveinsgnípa about 1900 m above sea level.

1813
The first mountaineering to Hvannadalshnúkur in 1813 may have been a misinterpretation. The Norwegian Hans Frisak doesn't mention Hvannadalshnúkur but according to descriptions of the view he has probably walked on the Hnappur mountain peak.

1891
During the most part of the nineteenth century people believed that Hnappur was the highest mountaintop in Iceland. This was until August 1891 when Frederick W.W. Howell walked to Hnappur and saw that the Hvannadalshnúkur peak is actually higher. He climbed Hvannadalshnúkur the same day along with Páll Jónsson and Þorlákur Þorláksson. Howell believed that Hvannadalshnúkur was about 1950 m above sea level.

1904
In spring 1904 surveyors lead by Johan Peter Koch officer in the Danish Army surveyed the height of Hvannadalshnúkur by using triangulation network based on already known ground stations that could be seen from the peak. Their outcome was 2119 m above sea level. This digit has since been in all school books and scientific journals regarding Iceland.

1955
More accurate surveys were executed after 1955. For example a triangulation network using another reference system was done in 1956 lead by J.W.K. Ekholm with the results of 2123 m above sea level.

1993
In spring 1993 the Science Institute of the University of Iceland and the Iceland Glaciological Society measured with DGPS (Differential Global Positioning System). Their result was 2111 m above sea level. However, the uncertainty in this survey is estimated to be about 5 metres.

2004
In June 2004, 100 years after the first survey on Hvannadalshnúkur, members of the Iceland Glaciological Society surveyed the height of Hvannadalshnúkur with accurate GPS equipment with the outcome of 2111 m above sea level.

2005
In July 2005 the National Land Survey of Iceland executed the most accurate survey that can be done at this time. The outcome was 2110 m above sea level.

Primary methods to survey mountain peaks until present days:

Triangulation network
When using the triangulation network, a network of known ground stations is used to calculate accurate position of new and unknown points with the rules of geometry. Surveyors stacked milestones in prominent places which were then surveyed and marked on maps. Later these points were used to estimate the height of the place to be surveyed. Imprecision in this type of survey is in the refraction in the air that deceives the eye of the surveyor.

GPS-surveying
Global Positioning Systems rely on communicating with many satellites that are in orbit around Earth. Imprecision in GPS-surveying can be due to interference in the aerospace, incongruence in clocks, etc. To minimize the uncertainty in surveys the GPS equipment must be on the same place during a certain amount of time.