For decades, geolinguists have been using cartographic materials to display their data and understand the spatial distribution of local dialects. They have used many forms of maps such as maps with labels, symbols or colors. The most widely used are maps with isoglosses which are hand-drawn boundaries defining areas where people share the same language feature. Our source data is a mesh of georeferenced survey points representing a region of interest and each point of the mesh has a phonetic form attached. The issue is to transform this survey point mesh into homogeneous areas sharing similar categorical values in order to identify spatial patterns. This paper describes interpolation methods implemented to produce isogloss maps, namely turning a sample of points into areas boundaries. Implementing such methods requires performing spatial interpolations on a qualitative data set. We also describe a new cartographic tool, ShinyDialect, made for geolinguists to automate the construction process of maps with isoglosses in order to use it as support for spatial analysis. First, we will discuss geolinguistic data and the limits of the existing methods to compute linguistic areas. Next, we will describe the spatial interpolation methods we have implemented. Lastly, we will present features of the tool ShinyDialect to help geolinguists to build accurate maps.