ACS MaxDistance

Question

ACS MaxDistance

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Hey,

I am having a hard time getting $maxDistance to work. I pass the following object to the "where" parameter in the cloud search:

var searchWhere = {
    lnglat =     {
        "$maxDistance" = 50;
        "$nearSphere" = [
            40.72760009765625,
            -74.00137329101562
        ];
    };
}

And the list of results still returns a location which is across the country (US) from where I am.

I read in another question here that $nearSphere needs floating numbers to work and that's what I'm passing -- my proof is that Ti.API.info(typeof searchWhere.lnglat['$nearSphere'][0]); returns "number" -- but Ti.API.info(searchWhere) prints this object:

{
    lnglat =     {
        "$maxDistance" = 50;
        "$nearSphere" = (
            "40.72760009765625",
            "-74.00137329101562"
        );
    };
}

And I can't tell if my problem is that $nearSphere is not getting floating numbers as values OR if there is something else wrong in my code.

Thanks.

2 Answers

Your Answer

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The full cloud query/search looks like this:
Cloud.Places.query({ per_page: 30, where: searchWhere }, function (e) { if (e.success) { callback(e); // renderSearchResults(e); } else { alert('Error: ' + ((e.error && e.message) || JSON.stringify(e))); } });

— commented 7 months ago by Stoyan Vasilev

Answer 1

Hi there,

max distance is expressed in degrees - I think that's the correct term. My technical geography is terrible - got no idea what that all means but I use this to find places in the map region displayed on screen. It's very crude but does an okay job

lnglat : {
                    "$nearSphere" : [longitude, latitude],
                    "$maxDistance" : (mapView.longitudeDelta + mapView.latitudeDelta) / 2,
                }
            }

Answer 2

I am going to answer my own question since I figured out the answer myself.

1) In the $nearSphere parameter I was passing [latitude,longitude] instead of [longitude,latitude].

2) $maxDistance is in decimal degrees.

I couldn't find a calculator that simply converts decimal degrees to miles but I figured out that 1 mile is approximately 0.000126 decimal degrees. Note that this is a really rough approximation and if you want exact values you should take into account that the earth is not a perfect sphere and calculate the distance based on where on the planet you are measuring this distance.