Consider the scenario where a person is applying for a liquor licence and the law stipulates: New liquor premises must be located at least five hundred meters (500m) away from schools, places of worship; recreation facilities, rehabilitation or retreat centers, residential areas and public institutions.
For this requirement Survey123 can be a valuable tool and in this blog post I will show you how you can enable this functionality in a Survey123 form:
Step 1: Create a new survey with Survey123 Connect
Step 2: Create a geopoint field in the main survey which will be used to capture the location of the new licence premises
Step 3: Create a repeated section to capture the occurrences of nearby schools, places of worship etc. Each with a premise type and a geopoint
Your survey design should look similar to this:
| type | name | label |
| geopoint | new_licence_location | New Licence Location |
| begin repeat | nearby_places | Nearby Permises |
| select_one category | place_type | Type of Premises |
| geopoint | nearby_location | Nearby Location |
| end repeat |
Step 4: Now, split both the coordinates sets into their x,y pairs and convert them to radians:
| calculate | gps_lat | gps lat | pulldata(‘@geopoint’, ${new_licence_location}, ‘y’) * pi() div 180 |
| calculate | gps_long | gps long | pulldata(“@geopoint”, ${new_licence_location}, “x”) * pi() div 180 |
Do the same for the nearby_location geopoint field.
Step 5: Use the X, Y pairs to perform the distance calculation (in meters) with the Haversine formula:
| acos(sin(${gps_lat_end})*sin(${gps_lat}) + cos(${gps_lat_end})*cos(${gps_lat})*cos(${gps_long}-${gps_long_end}) ) * 6371000 |
After having made some cosmetic enhancements and adding the 500m stipulation your survey should look like this:
Feel free to use and adapt as you require. Here is a link to the Survey123 Excel design file: Licence Application