*Article* **Usefulness of Plane-Based Augmented Geovisualization—Case of "The Crown of Polish Mountains 3D"**

**Łukasz Halik \* and Łukasz Wielebski**

Adam Mickiewicz University, Pozna ´n, Poland, Department of Cartography and Geomatics, 61-712 Pozna ´n, Poland

**\*** Correspondence: lukasz.halik@amu.edu.pl; Tel.: +48-61-829-6246

**Abstract:** In this article, we suggest the introduction of a new method of generating AR content, which we propose to call plane-based augmented geovisualizations (PAGs). This method concerns cases in which AR geovisualizations are embedded directly on any plane detected by the AR device, as in the case of the investigated "Crown of Polish Mountains 3D" application. The study on the usefulness of the AR solution against a classic solution was conducted as part of an online survey of people from various age and social groups. The application in the monitor version showing 3D models of mountain peaks (without AR mode) was tested by the respondents themselves. The use of the application in the AR mode, which requires a smartphone with the appropriate module, was tested by the respondents based on a prepared video demonstrating its operation. The results of the research on three age groups show that the AR mode was preferred among users against all compared criteria, but some differences between age groups were clearly visible. In the case of the criterion of ease of use of the AR mode, the result was not so unambiguous, which is why further research is necessary. The research results show the potential of the AR mode in presenting 3D terrain models.

**Keywords:** mountain geovisualizations; augmented reality; mobile devices; 3D visualization of landscapes; geomedium efficiency; relief representation; cartographic products

**Citation:** Halik, Ł.; Wielebski, Ł. Usefulness of Plane-Based Augmented Geovisualization—Case of "The Crown of Polish Mountains 3D". *ISPRS Int. J. Geo-Inf.* **2023**, *12*, 38. https://doi.org/10.3390/ ijgi12020038

Academic Editors: Wolfgang Kainz and Florian Hruby

Received: 2 December 2022 Revised: 11 January 2023 Accepted: 17 January 2023 Published: 22 January 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

### **1. Introduction**

Along with the development of technology and the introduction of mobile devices, such as tablets or smartphones, to the market, new opportunities to use maps and the derivatives of cartographic visualizations that apply the third dimension to present spatial data have arisen [1–3]. New map products have been emerging as a result of technological advances. Digital geospatial representation has been evolving in three areas: threedimensional (3D) spaces, real-time dynamics, and fusion of virtual and real objects [4,5]. Augmented reality (AR) has similar characteristics. The concept of AR was first introduced by scientists working for Boeing Company in the early 1990s to assist in mechanical assembly [6]. The important step in laying the theoretical foundation for the augmented reality system was to create a reality–virtuality continuum [7] in which AR could find its place. This paved the way for a further process of defining three fundamental features of AR by Azuma [8]: combining real and virtual, interaction in real time, and registered in 3D.

From a geographical point of view, visualizations that use AR can be divided into: augmented virtual environments (AVEs) or as augmented geographic reality (AGR) [9]. According to Cheng et al. [9] (p. 427), AGR should be divided, based on field experiences and maps, into augmented reality environments (AREs) and augmented maps (AMs), respectively. In AREs, visual information (e.g., digital tags) is added to objects in the real world to perform functions, such as navigation and illustration. AMs are maps on which multiple types of geographic information (e.g., models and multimedia files) are superimposed to enhance cartographic information transfer and users' spatial cognitive ability. AMs are a subgroup of cartographic products that use the marker-based tracking method [10].

The campus tour system prototype by Feiner et al. [11] is referred to as the earliest prototype of the ARE. The opportunities offered by ARE were also examined in the context of using classic visual variables [12] and those that were gradually appearing as a result of technological advance related to digital cartography [13] for designing signatures that demonstrate the distance of the topographic object from the observer [14]. Another example of an ARE is provided by the research of Fukuda et al. [15], who demonstrated a solution that uses handheld augmented reality systems for urban landscape simulation. Kourouthanassis et al. [16] presented the use of mobile AR on the smartphone, testing a travel guide named CorfuAR.

In 2002, Bobrich and Otto [17], for the first time, developed AMs that integrated paper maps and virtual geographic information. In this system, the map becomes the reference frame of multiuser interaction, and cards with a quick response (QR) code become the identification anchor points of virtual interaction tools. When listing examples of the opportunities that augmented maps (AMs) bring, one also needs to mention the research by Morrison et al. [18], in which the employment of AR technology in combination with traditional paper maps was compared. De Almeida Pereira et al. [19] noted that adding 3D AR representation at the top of a paper map can enhance users' abilities to perform spatial positioning and to read map data.

Two aforementioned methods of generating AR content (ARE and AM) fail to consider cases in which AR geovisualizations are located on a freely chosen plane detected by the AR device. It was possible to single out the new method of generating AR content thanks to the progress in the evolution of algorithms of detecting planes in the real world. For this reason, we suggested introducing the third group of geovisualizations, known as planebased augmented geovisualization (PAG), to the classification system. In such solutions, geovisualization is mounted on a freely selected plane identified by the mobile device. It releases the user from the necessity of handling a physical object (e.g., a map) that displays virtual content on its screen. PAGs are a subgroup of cartographic products that use the feature-based tracking method [10].

Until recently, AR solutions have been created and shared mainly as applications uploaded from dedicated stores and installed directly in the memory of the smartphone. Advances in technology have allowed one to establish a set of *webXR standards* that use the opportunities of web browsers of mobile devices. *WebXR* is a group of standards that are used together to support rendering 3D scenes to hardware designed for presenting virtual worlds (virtual reality, VR) or for adding graphical imagery to the real world (augmented reality, AR) on the Web (https://developer.mozilla.org/en-US/docs/Web/API/WebXR\_ Device\_API accessed on 18 November 2022) [20].

Numerous currently available models of smartphones are equipped to handle webXR, which allows one to assume that in the near future the number of users of such solutions is going to grow. It is also the reason why such applications should be developed in cartography as well. Nevertheless, similar assumptions should be supported by the research.

In the literature, one may encounter different solutions used for cartographic visualizations, starting with static 2D ones, surface three-dimensional, and ending with interactive ones [21]. The examples of publications that present land relief with the use of 3D and AR are as follows: studies by Siqueira [22] that apply this technology to teaching topographic surfaces; papers by Templin et al. [23] in which it is used as a supporting tool in "inland and coastal water zones" navigation; works by Brejcha et al. [24] that create augmented photographs resulting from the combination of DEM and a photo taken in the field. The research on moving around the virtual world by walking and teleportation is also known [25].

The usefulness of 3D geovisualization in the AR technology displayed with the use of the PAG method was the topic discussed in this research. In the research, the usefulness was defined by examining the preferred by users' way in which the landscape and topographic traits were explored for the collection of mountain peaks, visualized in AR

and using the PAG method, and without the AR mode, within one "Korona Gór Polski 3D" (The Crown of Polish Mountains 3D) application. The application tested included a 3D representation of the collection of mountain peaks, the so-called crown of mountains, i.e., the highest mountain tops in a given country, whose review and exploration is possible through the Web browser, on the smartphone (in AR), or, more conventionally, on the PC (without AR technology). The subjective feelings and impressions that application users had during the process of using both modes (AR/no AR) may decide upon what solution will be chosen more willingly; thus, we decided to test how respondents evaluated those two opportunities.

### **2. Aim and Questions**

The main objective of the research was to determine the preferences of users from different age groups related to the opportunity to watch a 3D model of the *Tarnica* mountain peak onscreen in the AR mode (using the PAG method) and without AR. To meet this objective, researchers prepared an online survey, which allowed them to test the application, based on a set of objective and subjective questions, and ask users' opinion concerning it.

An online survey is a method of testing used on application users that offers the opportunity to reach the largest group of respondents of different ages and from different backgrounds. The survey proves to be a useful tool for obtaining opinions concerning the tested cartographic products regardless of whether researchers need the opinions of experts or amateurs [26,27]. Based on the appropriate structure of surveys, one may obtain answers from users related to their subjective evaluation of cartographic visualizations and objective effectiveness determined on the basis of the tasks completed [28]. In this research, we focused on subjective feelings that matter significantly because, for the large part, they determine whether or not a specific cartographic product meets with interest and is going to be willingly used. To make it more precise, the objective of this research raised the following questions:


### **3. Materials and Methods**

To meet the objective and answer the above questions, we adopted six main research stages:


### *3.1. The "Korona Gór Polski 3D" Application*

The "Korona Gór Polski 3D" (The Crown of the Polish Mountains 3D) application is an original application developed by the authors. The application uses webXR standards that make it work directly in the web browser, without the necessity of installing files. It is available to anybody, free of charge, at the following link: https://kgp3d.amu.edu.pl (accessed

on 29 November 2022) The purpose of the application is to demonstrate 28 3D models of mountain peaks on the territory of Poland, located in different mountain ranges referred to as "Korona Gór Polski" [29,30]. The application may be used on a PC or smartphone screen. Figure 1 presents an example of the view in the application on the screen of the mobile device. Figure 1a shows the application's welcome screen, with the option to select a 3D model of the mountain peak, 1b demonstrates a given peak with the option to display it in the AR mode and 1c presents the same peak in the AR mode. is available to anybody, free of charge, at the following link: https://kgp3d.amu.edu.pl (accessed on 29 November 2022) The purpose of the application is to demonstrate 28 3D models of mountain peaks on the territory of Poland, located in different mountain ranges referred to as "Korona Gór Polski" [29,30]. The application may be used on a PC or smartphone screen. Figure 1 presents an example of the view in the application on the screen of the mobile device. Figure 1a shows the application's welcome screen, with the option to select a 3D model of the mountain peak, 1b demonstrates a given peak with the option to display it in the AR mode and 1c presents the same peak in the AR mode.

an original application developed by the authors. The application uses webXR standards that make it work directly in the web browser, without the necessity of installing files. It

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— To choose age groups for the result analysis (Section 3.3); To present a statistical analysis of the results (Section 4).

*3.1. The "Korona Gór Polski 3D" Application*

**Figure 1.** View of the tested application displayed on the screen of a smartphone (**a**) with the initial page enabling the selection of a mountain peak; (**b**) the 3D model of the *Tarnica* peak displayed without the AR mode; (**c**) the 3D model of the *Tarnica* peak located on the top of a coffee table in the AR mode using the PAG method. **Figure 1.** View of the tested application displayed on the screen of a smartphone (**a**) with the initial page enabling the selection of a mountain peak; (**b**) the 3D model of the *Tarnica* peak displayed without the AR mode; (**c**) the 3D model of the *Tarnica* peak located on the top of a coffee table in the AR mode using the PAG method.

Technologically, the application is based on the *model-viewer* library (https://modelviewer.dev accessed on 27 November 2022) [31]. It offers the opportunity to view 3D models of specific mountain peaks, both on a monitor and smartphone screen, in the classic mode or in AR, provided that the device is equipped with the ARCore module. The Technologically, the application is based on the *model-viewer* library (https://modelviewer. dev accessed on 27 November 2022) [31]. It offers the opportunity to view 3D models of specific mountain peaks, both on a monitor and smartphone screen, in the classic mode or in AR, provided that the device is equipped with the ARCore module. The application has the same functions both on PCs and mobile devices, but the there are differences in how the 3D model is navigated on the mobile device with a touch screen vs. on the PC. Those differences are presented in Table 1.


**Table 1.** Comparison of the operations and capabilities of the tested application according to three modes of use: on a computer screen (PC), on a smartphone without AR, on a smartphone with AR.

The first difference is related to the size of the screen on which the 3D model is presented. For PC monitors, the difference is much greater than for smartphones. Only some monitors are equipped with a touch screen (i.e., interactive monitor) function, which is actually the fundamental feature of smartphones [32]. To change the scale of the 3D model on the classic monitor, one needs to use the scroll mouse and on the smartphone a two-finger move (changing the distance between them increases or decreases the scale). In the application displayed on the PC monitor, the rotation of the 3D model in the application used on the smartphone, in the no AR mode, is related to the scrolling move of the finger on the screen, whereas in the AR mode, the rotation is possible with the use of two fingers and making a circular movement with them.

When it comes to the opportunity to change the location of the 3D model in relation to the observer, the model remains in the center of the monitor for the whole time by default. As far as the smartphone (without AR) is concerned, a quick double tap on the screen moves the model. In the AR mode, the user may move the 3D model freely, moving the finger on the touchscreen to a freely selected part of the screen. When the application is used on a PC monitor, the location of the model remains fixed in relation to the observer like on the smartphone without the AR mode. The AR mode is related to two types of the observer–3D model relation. The first one assumes a fixed location of the operator in relation to the

model. It is actually a situation, in which, initially, users find a plane on which they want to display the model, rotating and scaling it to adjust it to the plane appropriately. The second type of the observer–3D model in the AR mode relation is directly related to viewing the 3D model in that mode after it is mounted on the selected plane.

The application's modes of use differ in the ways the model may be explored. In the monitor mode, the observer may watch the model from a distance like on the smartphone without AR. However, when the AR mode is on, the observer has an opportunity to enter the model, i.e., by making a large close-up or by stepping onto the plane the model is mounted on if the model is on the floor.

### *3.2. The Subject of the Study and the Online Survey*

The 3D application, presented in Section 3.1, works on mobile devices in the AR mode or without the AR mode (compare with Table 1). However, to be able to collect unified data, independent of the parameters of the mobile device, we decided that respondents would study the following material: the application that was displayed on the PC screen without AR and the demonstrational video on using the application on the smartphone in the AR mode. This approach allowed us to carry out the study on a bigger group of respondents. Regardless of the technical abilities of the mobile device that the respondents had, it was how they could see how to use the application with the AR technology with the PAG method applied. The preferences of the users who selected either the AR mode or no AR mode while answering questions, according to the traits that were included in the comparative criteria, constituted the object of research. In order to collect all of the data, an internet survey was designed.

The research survey was constructed in Limesurvey (internet survey tool) and consisted of four metric questions and two task sections with 6 subjective questions, based on the Likert scale [33]. Firstly, the data regarding respondents were collected (sex and age). In addition, respondents were asked about the AR term and previous experience related to the application that used that technology. The interaction between the user and the 3D model of the mountain peak *Tarnica* without AR (Figure 2b) was the next step. This was the rotation of the peak, closing it up and switching on and off the layer that showed the area visible from the peak. This was supposed to familiarize users with the way the application (and some selected elements of its functioning) is handled.

Figure 2a depicts the welcome screen of the application displayed on the monitor in the web browser in which respondents had to select a mountain peak from the list. Figure 2b presents a view of the selected 3D model.

Then, the respondents were asked to watch a video that showed how to use the application in the AR mode (Figure 3). Due to the registration of the real image and of the image displayed on the smartphone screen, functioning in the AR technology, each respondent had an opportunity to see what operating the 3D model looked like and what opportunities to view/operate it in that mode were available (https://youtu.be/E\_t8ZU2 OtMY accessed on 29 November 2022). To demonstrate how the AR mode worked, a Samsung Galaxy S20 smartphone was used.
