THE REPUBLIC OF BY Clifford J. Mugnier, CP, CMS, FASPRS LATVIA The Grids & Datums column has completed an exploration of every country on the Earth. For those who did not get to enjoy this world tour the first time,PE&RS is reprinting prior articles from the column. This month’s article on the Republic of Latvia was originally printed in 2002 but contains updates to their coordinate system since then. etween 2500 and 1500 BC, the Finno-Ugric and proto-Baltic tribes settled on Baltic Bshores. The closest ethnic relatives of the Latvians are the ancient Prussians, the Galinds, the Jatvings, and the Lithuanians. The first settlers in the territory of Latvia were the Livonians or “Libiesi.” The Livonians were once concentrated in the northern part of Latvia, but today only about Delivered by Ingenta 100 individuals speak theirIP: ancient 192.168.39.151 language On: Thu, 23 Sep 2021 19:59:43 which nevertheless hasCopyright: contributed American to a Societyprominent for Photogrammetry and Remote Sensing Latvian dialect. By the 12th century, the natives network of 1820-32 in Semgallen and Courland, and were were split into a number of tribal groups, all published by Czarist Russia in 1843 and 1847. Tenner later practicing nature religions. The Knights of the supplemented his primary net with lower-order stations. The Tenner chains were originally computed on the Walbeck 1819 Sword (Livonian Order) were crusaders that ellipsoid where the semi-major axis (a) = 6,376,895 m and forcibly converted Latvia to Christianity in the 1/ = 302.7821565; they were later recomputed on the Bessel th f 13 century. For centuries, Latvia has been under 1841 ellipsoid. Between 1878 and 1884, Schulgin further in- Swedish, Polish, German, and Russian rule. In creased the density of lower-order stations in the area origi- 1918, Latvia proclaimed independence from Czarist nally surveyed by Tenner. However, the majority of these lat- Russia. By 1940, Latvia was occupied by the Soviet ter station monuments did not survive into the 20th century, Union and was soon overrun by Nazi Germany. and they were ignored by the Russians. The Tenner net in the Soviet forces reoccupied the country in 1944-45, east did not extend further north than the Sestukalns-Gaiz- and Latvia remained under Soviet rule until 1991 inkalns side, and the Struve primary net extended north from this side through Yuryev and over the Gulf of Finland. when it was admitted into the United Nations. In The Russian Western Frontier surveys were executed mainly May 1994, the Latvian National Independence by Yemel’yanov and Nikifirov between 1904 and 1912. These Movement finished first in Latvia’s first post-Soviet chains formed a major part of the modern (early) 20th century local elections; the excommunists fared the worst. network of Eastern Latvia with some of the first-order sta- Latvia shares borders with Estonia to the north (343 km), tions being old Tenner or Struve stations. This Russian sur- Russia to the east (246 km), Belarus to the southeast (161 km), Lithuania to the south (588 km), and the Baltic Sea Photogrammetric Engineering & Remote Sensing and Gulf of Riga to the west comprises a coastline of 498 km. Vol. 86, No. 10, October 2020, pp. 599–602. Slightly larger than West Virginia, the country is mostly low 0099-1112/20/599–602 coastal plain with the highest point being Gaizinkalns at 312 © 2020 American Society for Photogrammetry meters. and Remote Sensing Survey activities in Latvia began with Tenner’s first-order doi: 10.14358/PERS.86.10.599 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING October 2020 599 October 2020 Layout.indd 599 9/17/2020 11:46:08 AM vey covered much of western and central Deflections of the Vertical in Latvia Livonia in 1904-05, and eastern Livonia and Lettgallen were covered with the 1906 Because of the ground- and 1912 nets. Lower-order nets to fourth breaking work the order supplemented the primary chains. University of Latvia’s These Czarist Russian surveys were com- Institute of Geodesy puted on the Pulkovo 1904 Datum or the and Geoinformatics Yuryev II Datum, both of which are refer- published on their re- enced to the Bessel 1841 ellipsoid where a 1 search to develop a = 6,377,397.155 m and /f = 299.1528128. one-centimeter geoid After Latvia achieved Republic status, model and the inven- the new Latvian Survey Office began to tion of a relatively unify these various nets in stages, before inexpensive Digital commencing with their own survey activi- Zenith Camera (DZC) ties in 1924. The results of this program of by Dr. Ansis Zarins, unification are published inLatvijas Valsts I traveled to Riga a Trigonometriskais. The Pulkovo 1904 Da- couple summers ago. tum points were recomputed into Yuryev LSU’s Center for II Datum based on 14 available first-order GeoInformatics had Scharmhorst points, and this was then acquired an absolute put into the Senks Soldner Grid. The 1905 gravity meter along Russian net had already been computed with a couple relative on the Yuryev II Datum, and was accept- gravity meters and ed into the Old Gaizinkalns Soldner Grid various related instru- where jo = 56º 52´ 15.184˝ N and lo = 25º ments and vehicles 57´ 34.720˝ East of Greenwich. No false with the same objective for the State of Louisiana. DeliveredSince their by DZC Ingenta only origin was used. Similarly, the 1906 and IP: 192.168.39.151 On: Thu, 23 Sep 2021 19:59:431912 nets were already on the Yuryev II works at night with clear skiesCopyright: for star American shots, days Society were openfor Photogrammetry for the staff and Remote Sensing to take me around Riga and environs. A major point of interest for me was Datum, and those form the Old Vitoleieki the origin of the Yuryev II Datum and the General Latvian Triangulation Soldner Grid where jo = 56º 40´ 08.64˝ N , Net Datum Origin is Riga St. Peter’s Church (top of the Riga Church spire). lo = 27º 15´ 11.79˝ East of Greenwich, and no false origin was used. Tenner’s survey The Latvian Geodesists then took me inside of the church, and a plaque had been calculated on the Walbeck 1819 in the floor of the vestibule, directly under the plumb line of the spire dis- ellipsoid and was now recomputed on the played the actual Datum Origin: Bessel 1841 ellipsoid and controlled by the Yemel’yanov-Nikifirov survey of the Puci-Sarmes side. This had the effect of introducing a slight swing to the orienta- tion of the Tenner triangulation. The Lat- vian Kulkigan and Puci systems cover this net. For most of eastern Latvia, the earlier Russian surveys could be used to form the basis of the Latvian triangulation as the station centers could be found. In Courland and Semgallen the original triangulation dated back to 1820 and few of the old sta- tions could be recovered. This necessitated a complete new survey, which was started in 1924 from the Liepaja-Paplaka base and By the way, their DZC worked flawlessly, and LSU purchased one for extended in stages to the Puci-Sarmes side €100K, including training. Our DZC is currently kept busy here in Loui- and thence to Riga and Jelgava. The origin siana observing the deflection of the vertical at all of our GPS CORS sites. of this system is the Yuryev II Datum val- ue of Riga St Peter’s Church “tower ball” which is the same station as the Tenner first-order point. The Yuryev II Datum azi- 600 October 2020 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING October 2020 Layout.indd 600 9/17/2020 11:28:39 AM muth to Jelgava Church was adopted for the orientation of the Provisional Courland System geographics and the General net. Although the Riga Church and Courland values are the Latvian Triangulation Net. However, care is taken in the Lat- same as Scharnhorst value and the azimuth is identical, the vian “Trig” Lists to show from which geodetic system the Riga coordinates of Jelgava Church vary slightly by 0.002˝ in each Cassini-Soldner coordinates are computed. axis. This was due to the scales of the Liepaja and Jelgava bas- During these inter-war years, the Russians were also ac- es, which were adopted for the Courland System in preference tively recomputing their survey information in the Baltic to the less reliable Scharnhorst scale. This became known as states. Prior to 1932 the Russian horizontal control of the the “Provisional Courland System (datum).” The Provisional Baltic States was always referenced to Dorpat Observatory Courland System was divided into two Cassini-Soldner Grids: at Tartu in Estonia. In 1932 the Russians set up Pulkovo Ob- The “Riga System” with its origin at Riga St. Peter’s Church servatory 1932 as their horizontal datum and origin reference where jo = 56º 56´ 53.919˝ N and lo = 24º 06´ 31.898˝ East to the Bessel 1841 ellipsoid, and later revised this to Pulkovo of Greenwich, and the “Vardupe System” with its origin at 1942, now properly termed “System 42” (datum) referenced to the Provisional Courland station Vardupe where jo = 56º 51´ the Krassovsky 1940 ellipsoid. 32.961˝ N and lo = 21º 52´ 03.462˝ East of Greenwich. No false Thanks to E.A. Early of the U.S. Army Map Service, “In origin was used for either grid. The Provisional Courland 1942 the German Army undertook the conversion of the Lat- System was immediately adjusted and computed before the vian Soldner coordinates to DHG Pulkovo.” (Deutches Heeres triangulation of central and east Latvia was completed. This Gitter – German Army Grid) “The first phase of the conver- Provisional Courland System was first adjusted within itself sion embodied the change of projection from Soldner to Gauss- and then adjusted to the Latvian part of the Baltic Ring.