Development of Latvian national 2nd order leveling network

Latvian National First Order Levelling Network consist of 15 polygons and 51 lines and was re-established in 2011. From 1^st of December of year 2014 in Latvia Republic is new Latvian normal height system at epoch 2000, 5. Normal heights are widely used in origination and application of geospatial data in civil engineering and quasigeoid computation etc. The main objective of this work is to describe 2^nd order leveling network development idea, purpose and process. Essential of work is option, check, used and analyze historical height data, which has all Eastern European countries, and newly measured height data.