Mobile Apps for Foot Measurement in Pedorthic Practice : Scoping Review
individual items that were found during the review of the included foot measure apps relevant to the same goal . The finalized rating tool model with the updated overarching domains and individual category items are illustrated in Table 1 .
The key domains essential for evaluating foot measurement apps were identified as follows : app classification , aesthetics , general features , performance and efficiency , usability , measurement-specific functionality , transparency , subjective quality , and the app ’ s perceived impacts on users .
The app quality criteria clustered around the domains , excluding the metadata section , were used to build the app rating scale . Depending on the type of question asked to assess the criteria , each item can score a response as a 5-point Likert scale or a binary response ( 1 or 5 ). Cases were found in certain categorical items that were not applicable ; thus , the “ not applicable ” rating was introduced to the scale . Other cases displayed complexity in gaining access to certain types of information , and therefore a rating option “ unknown ” was added . A few subscale items were excluded from the quantitative measurement since they provided qualitative descriptions about apps that could not be weighed quantitatively . These items are the app metadata domain items , applicable age group item , and app subcategory item .
App Metadata
General information about the apps was abstracted as app metadata from the respective app stores under the app classification category . App metadata include information such as app platform , app URL , store rating , store description , number of downloads , developer information , and origin . However , this information has no impact on the rating scale . App metadata were extracted systematically by two investigators from each app store on a Google Sheet and this dataset was cross-verified by a third investigator for data anomalies .
App Classification
Through an extensive review of prior work on foot measurement and related technologies [ 20-23 ], the apps were subcategorized depending on their type of functionality into the following groups : ( 1 ) simple size-unit converter , ( 2 ) 2D foot scanner , ( 3 ) 3D foot scanner , ( 4 ) shoe recommender , ( 5 ) foot tilt calculator , and ( 6 ) foot progress tracker .
Subcategory 1 ( simple size-unit converter ) apps are the simplest type of apps that take user input values for foot shape and dimensions to produce another category of size or shape , which can be related to both shoe and foot properties . Subcategory 2 ( 2D foot scanner ) apps are more advanced in comparison as they use imaging sensors to acquire 2D data about foot images and use algorithms to compute the user ’ s feet dimensions . The 3D scanner apps ( subcategory 3 ) generally require state-ofthe-art techniques and external hardware such as 3D imaging sensors or dimensional digitizing devices . This type of app is generally capable of providing an array of user feet dimensions . The shoe recommender ( subcategory 4 ) and foot tilt calculator ( subcategory 5 ) apps are modified versions of 2D and 3D scanners that do not directly output raw measurement information but rather transform this information into more consumer-friendly , useful views , and derived information . Foot progress trackers ( subcategory 6 ) are common apps that were not specifically designed for applications to feet , but this category was nevertheless included in the study because of the ability
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