# A Multilevel Road Alignment Model for Spatial-Query-by-Sketch
## 1 Introduction  
With the widespread availability of the internet, people can create, publish, or query spatial data through web-based geographic information systems (GIS), such as volunteered geographic information (VGI) [1]. Geographic information systems can store, analyze, and visualize a variety of spatial information. They help for resource management, navigation, decision making, etc. Spatial query is one of the commonly used means of manipulating geographic information for individual citizens. It refers to query based on object's name, location, distance, etc. However, existing spatial query methods for general users are usually based on single attributes, such as the feature's name--finding a building named \"Hotel\", or distance between features--finding the nearest hotel. However, if you want to find a hotel with amenities such as restaurants, shopping malls, etc. in its vicinity, a spatial combination of multiple attributes (distance, name, etc.) is required. However, existing geographic tools for common users cannot perform this query, such as Google Maps. Professional GIS tools, such as QGIS ([[https://qgis.org/en/site/](https://qgis.org/en/site/)]([https://qgis.org/en/site/](https://qgis.org/en/site/))), implement this query by first creating the hotel's buffer, and then calculating the intersection of that buffer with the restaurants, shopping malls, etc. This process is obscure for the average users. The key to solving this problem is whether it is possible to find ways of human-computer interaction that are close to human's daily communication methods and can be understood by GIS systems, so that humans can communicate with computers in the same way as their counterparts [2]. A sketch map outlines a place/area/region in a drawing where the mappers represent the more characteristic elements according to their point of view. In 1948, [PERSON] categorized sketch maps as cognitive maps [3]. Sketch maps often reflect a strong correspondence between the spatial relations in the map and the environment and the interaction interfaces between people and their environment [4]. Individuals can create sketch maps simply by drawing an object on a paper or on a touch-sensitive screen by using a drawing software. Spatial-query-by-sketch (SQbS) [5] aligns the objects in a sketch map with those from different spatial databases. It translates a sketch map into a symbolic representation and processes it against a geographic database [6]. For example, the SketchMapia framework [7; 8; 9] can be used to identify seven invariant sketch features to find out a correspondence between the sketch maps and metric maps. In this framework, qualitative constraint networks based on existing qualitative calculi are compared to match the spatial objects and a new structure involving the local compatibility matrices is used to ensure partial matching and high accuracy. SQbS is a convenient tool for regular individuals owing to the following advantages: (i) individuals can conduct a spatial query without any particular background technical knowledge; (ii) in contrast to traditional query methods, which focus on a single attribute query, the approach supports scene queries; and (iii) in contrast to text queries, this approach is a more intuitive and natural query method that displays all the features. SQbS have the potential application in navigation [10], 3D shape retrieval [11], facilitating crime scene identification [12], etc. However, according to [PERSON] [13], only a small quantity of objects (12-17) appears in a sketch, where human-built objects (e.g., roads and buildings) are often given more relevance than natural objects (e.g., green spaces). In addition, in [PERSON] and [PERSON] [14]'s study, aspects that are visibly, semantically, or emotionally significant for them are usually given more priority, and as [PERSON] et al. [15] pointed out, the aspects that mappers consider \"uninteresting\" are usually simplified.