In designing a mobile app which allows to search for nearby places through geolocation, distance is important. In fact, the concept of proximity is relative, and it depends from distance itself. So, I want to design a mobile app to search places, and I know that my target users are used to walking to these places, so I thought to set default distance in 500mt/1km. My question is, when user performs the geolocation-search, do I have to inform them how much is the default distance? This doubt arises from the fact that , by changing the distance settings, the app can show more places in the map. Of course there is a filter sections (to perform a filtering search, even changing distance), but I don't want to fall in error by not giving users any results merely because the default distance is too low.
Number of search results!
Setting a distance will give varying results. Rather, you'd search for an optimum number of search results. This will always give the user:
Remember, you're showing the closest items, not items within walking distance, because you don't know what counts as walking distance for each user. My mom won't walk as far as I do, for example.
You could consider giving them an estimated time to the goal to make it more useful, but don't exclude anything because you might be right at that cut-off where Person A would walk it but person B wouldn't.
This is as opposed to not getting any results if nothing's close enough. It takes into account cases like, for example, rural Australia, where some cities can be many hours of traveling away, but also places like New York, where there's always bound to be something close by.
Number of search results?
Additionally, you know how with Google people don't look at search results beyond the first page (or only rarely?) so you might want to do some research into that behavior for your app. Will users look through amount X or amount Y of results? If there's a cutoff point, great! That's the number of results you should show.
Instead of setting a default value, I would recommend just showing the results and allowing the users to sort by the service required so that they get more accurate results as this example shows
Restricting to a minimum value can cause your users to miss out on great restaurants or places to visit nearby if the restaurant or place is just out of your proposed walking range.
However since your focus is on easy access ensure the results are shown in ascending order of distance.
Lastly, your proposed walking range might not be applicable to all users as some users might not mind walking long distances to find something they like.
Here is another example of an app which employs a similar design
However if required you can provide users the option to specify a minimum filter as this app does to show results only for that distance range
Absolute distance measurements are hardly assessed by people, it's better to use more tangible measure unit, which is time.
Google Maps use both parameters for car and walking routes (Google asumes walking speed is about 4.5 km/hour), and time only for public transport routes:
People search for objects, not distance. The distance affects the decision. If the distance too big for someone, he just refuse that object. So displaying default distance is not so important. Again, people search for objects. You could display distance in more useful way: