Ever since around 1788 to 1789, when he was a private student of Professor Johann Georg Tralles at the Bernese Academy, Hassler showed an intense interest in national surveying. In view of the national survey of Switzerland, he financed the two first measurements of the baseline in the "Grosses Moos" in 1791 and 1797. Several triangulation measurements were connected to this first length scale. An authentic coordinate list of that time includes the latitude and longitude of 51 points between the Moléson and the Chasseron in western Switzerland and along a line from the Hörnli to Hohentwiel in the east. Even though no maps resulted from these geodetic bases, they are indeed significant preliminary efforts for such work.

During the Helvetic (Swiss) Republic, Hassler was commissioned by the minister of finances to establish a list of all existing maps and plans. In January 1799 he submitted an exposé "Ueber ein Vermessungsbureau", which can be regarded as a scientific concept for national surveying. A synopsis of its content could be translated as follows: the accurate knowledge of the territory is a prerequisite for a government with respect to its interior administration; nothing can provide this information, show each part of the country, and the needs and resources of each, than an accurate and systematic survey of the entire country, combined with stat(ist)ical and economic tables which should systematically contain all national information (except the situation) that could in any way be required for the purpose of governing the nation. From the political point of view, Philipp Albert Stapfer, Swiss minister of fine arts and sciences, had already called for the founding of a cadastral bureau or a bureau for geodetic work in the summer of 1798. Hassler would have had the abilities and education to head such an institution, however, during those unstable times when the Helvetic Republic was shaken by national crises, these prospective ideas were unfortunately never realized.

The government of the "one and indivisible Helvetic Republic" named Johann Georg Tralles as representative to the international committee for determining a new weight and measurement system in Paris in the summer of 1798. He brought back to Bern two examples each of the so-called committee meter and the committee kilogram. One specimen of each of these "archive meter and kilogram" was used as the primary measure for Switzerland during the following decades. In 1801 Tralles culminated his position as the Swiss expert in matters of weights and measures with his report on the definition of the basic unit of the metric system, which had already been adopted by the Franconian Republic, and which lead to the passing of the respective laws in that same year. Thanks to his proximity to Tralles, Hassler was always well informed about the latest developments in the subject of weights and measures. When he traveled to America, Hassler even brought along the other specimen of the committee meter. He had about the same impact on the system of weights and measurements for the United States as Tralles did for Switzerland years before. If anything, Hassler is one of the first scientists of outstanding significance in American history.

In February 1803 – shortly before the signing of the "Mediations Act" – Hassler expressed his ideas On establishing a measurement system in the Canton of Aargau to the government of the canton, which did not even discuss these opinions. The fact that his already developed and farsighted ideas in surveying were not accepted, and the degrading personal experiences which he made with the "liquidations commission" of the Helvetic Republic upon requesting reimbursement for his expenses while carrying out his governmental commission in national surveying all added up to the result that Hassler emigrated to America in 1805 because he couldn't see any personal future in a "Switzerland by the grace of Napoleon".

There are no known maps from Hassler during his time in Switzerland. However, it is known that he took a three-dimensional relief model of the area around the Mont Blanc to the United States with him. He seems to have adapted a similar method of working as Joachim Eugen Müller from Engelberg, who used to make plaster models of the terrain he was surveying for the Atlas Suisse directly on site, and then convert these at home into a landscape drawing. Large parts of America were topographically surveyed and mapped by Hassler.

In the course of his lifetime, Hassler had worked in all fields pertaining to geodetic and topographic surveying and the cartographic representation of territories. He was active in higher geodesy (astronomic positioning, baseline measurement and triangulation), the standardization of units of measurement, techniques in topographic surveying (relief models, introducing the plane table in America), cartographic projections, and building instruments. Primarily, however, Hassler was a pioneer in that national surveying became one of the central tasks of a modern nation. Even though he had not yet been successful in Switzerland, he was finally able to implement in America years later and after persistent battles against all kinds of obstacles and adversities, the establishment of national structures for the two domains of land and coastal surveying, and standardizing weights and measures.

The problem of the traceability of observations to so-called standard units was to follow Hassler his whole lifetime. His great merits in the field of metrology, however, were evident mainly in America (1832-43). The pace of America's trade with foreign countries picked up in the 19th century and the resulting customs and tariffs called for national and international comparisons of the most varied units of measure. Hassler investigated the volumes, lengths and weights of the different units used in America in those days. He carried out these investigations at 47 different customs stations and reported his results (Comparisons of Weights and Measures of Length and Capacity) to the Senate in 1832. He played a decisive role in founding the Bureau of Standards and became its first superintendent.

Hassler also developed aids for taking more accurate measurements, and instructed designers in how to apply his ideas. Even before he emigrated to America, he cultivated lively contacts with renowned European geodesists, mathematicians and other scientists. Hassler maintained these contacts through letters and trips to Europe, which assured him access to first-hand information about the sciences and the art of making instruments. These circumstances proved to be an advantage for the Bureau of Standards, since it was always at the source of the newest standards.

One of Hassler's characteristics was that – despite adverse conditions – he never gave up and pursued his visions and their application with the persistency of a pioneer. He was always able to transform his great theoretic knowledge into practical applications, and with this reasonable and mutual interaction between theory and practice, he made a decisive contribution to scientific progress. This distinguishes him as one of the internationally eminent personages in the fields of surveying and metrology.

The seal of
Ferdinand Rudolf Hassler