In the era of the high level of technological achievements of remote sensing of the Earth and the high level of development of web cartography, interactive web applications for the analysis of data of remote sensing of the Earth are gaining more and more popularity. Considering the large amount of space image data, and the complexity and heterogeneity of the analysis tools that need to be developed, the question arises of quickly and efficiently creating an interactive web application for the analysis of space images that will help scientists monitor and study changes in the Earth's surface and predict optimal ways of territory development with minimal expenditure of time and resources. In solving such a question, the specialized web platform Google Earth Engine (GEE) can help. The purpose of the article is to highlight the characteristics and advantages of the GEE platform by creating an interactive web application using the example of analysing changes in the NDVI index. Analysing GEE allows us to conclude that this web-platform provides a comprehensive solution for creating interactive cartographic web applications for the analysis of space images with a built-in IDE. It will help to significantly reduce development time and costs, allowing for quick and efficient analysis of Earth remote sensing data.

Geoportal.lt is a Lithuanian state information system whose scope is to allow all data users to freely access geographic data, maps and e-services. The portal also allows drawing relief altitude profile and set the altitude of point on location. It is performed by applying the tool “Set altitude of point on location”. It is one of the newest tools of geoportal.lt website, whose accuracy has not been analysed, and which, according to the information provided by GIS Centre, complies with the requirements set for 1:50000 scale maps. This tool is selected as an object of research, while the aim of the research is to analyse the accuracy of data provided by Lithuanian spatial information portal tool “Set altitude of point on location” in case of different land covers. The following methods of investigation have been employed: literary analysis; the analysis of cartographic material; field measurements and data processing; comparative analysis of data. The data is processed using Geomap and Microsoft Excel programmes. After the analysis has been carried out, it was established that the most common errors in all types of land covers are from 0.5 m to 1.5 m. Such errors comprise 70 per cent in forest areas, 35 per cent in built-up territory, and 53 per cent in thin land cover. Taking into consideration that the website geoportal.lt operates on the basis of orthographic map whose accuracy is 1 meter and the discussed tool shows the altitude of the nearest known point, it can be stated that the obtained presumptions are permissible. To summarise the obtained data, the tool is reliable. The reliability of the data is 91 per cent in thin land cover, 86 per cent in forest area, 75 per cent in built-up area. To compare it with topographic maps of analogous format, where the errors of altitudes may reach up to 10 meters, the tool is reliable even in case of major errors.